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Vorshlag Budget 2015 TT Build: Project DANGER ZONE

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Project Introduction, Dec 18th, 2014: Welcome to Vorshlag's latest crazy project build thread. Many of you know how we have documented our various project builds on the forums over the past 12 years and this will be another fun one. I will be cross-posting this on a number of forums, shown in the list below. Pick your favorite, subscribe, and feel free to join in the conversation! If you've never seen my build threads before, there are links buried throughout (usually in bold) as well as LOTS of pictures. Click on any picture posted and it usually goes to a larger resolution version. I will embed car construction and race videos as well.

Before we get started I have to admit that this is just an introductory, background laying TEASER post. In it I will describe in basic terms what we are doing, and why, but we ARE NOT revealing what this new TT build car is until AFTER our first time trial competition event (NASA at MSR Houston Jan 17-18, 2015). Why? Everyone likes surprises, and I want to spring this on our competitors before they pitch a fit and leave the class, hehehe! This car will be built to run in a NASA Time Trial "letter class" (something from TTB to TTF) as well as SCCA Club Trials (when the two clubs' events don't overlap). We might sneak it into a few other series and classes, if it looks like a good fit.


Who Are These Vorshlag Guys?




Some of you know Vorshlag (primarily a suspension parts manufacturing and supply company + street/competition prep shop) from our various online build threads, like our 2011 Mustang GT, shown above. We purchased this "test mule" to use for parts development, and with it we tested with 3 brands of shocks (AST, Moton and MCS), all with custom valving. We developed our second revision of the S197 camber plate set-up, helped Whiteline develop and test lots of parts, developed an 18x10" D-Force wheel for the S197 chassis, and tested and race proved Forgestar wheels, among other items.


We tested these things by campaigning it in various racing groups over the past past 4 years (GTA, SCCA, NASA, USCA, Optima, Goodguys) and it was extremely competitive in the last 2 seasons in NASA's TT3 class, with dozens of wins and setting 13 NASA class track records. We also won with this car in Optima/USCA, SCCA Club Trials, Goodguys autocrossing, and more. All of the development on this car has been shared on this Project Build Thread, but that car is currently for sale (here) and off limits to me on a race track from now on. We kind of went overboard on the custom fabrication and suspension work with that build, so somebody is going to get a smokin' deal when they buy it.


Low Budget Build This Time


This Mustang was an example of Winning at All Costs. While we could have spent even more on it, we focused our expenditure where it would help performance the most. We used the best suspension, high end aero parts, lots of custom body mods, and we ran on brand new "sticker" sets of Hoosier A6 tires ($1700 worth per weekend) at each event to guarantee success. Maybe we over did it... we set every TT3 track record for 2 years on the NASA Texas calendar and in 2014 had win margins over 2nd place by 5-7 seconds on most race days. Overkill costs extra. This DANGER ZONE project will be more about Winning with Low Costs, spending just enough to get that win, without massive overkill modifications or needless expenses. The inherent nature of the TT lettered classes limits our ability to go hog wild with spending or mods, too.


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Our TT3 Mustang was a big brawler - we ran it HEAVY, with the biggest tires Hoosier made, and with huge aero


We learned a lot of valuable lessons with the TT3 build, with breakthroughs and mistakes. We noticed what was worth the cost, and what was not, and shared these lessons publicly. While we had generally excellent results the last 2 years, the first 2 years of competition were a bust (poor planning on my part put it into the wrong series & wrong class), and even in 2014 I made a critical error that caused a high speed off (ran out of brake pad material & overheated the fluid). That little shunt at Road Atlanta caused some injuries to my back, but barely hurt the car or the splitter - this car is a tank! I am not keen to repeat those mistakes - so we will use all the test data we can get and over-do the safety aspects on this car (spending far more on safety upgrades than are required in Time Trial - so I'm not counting that in the "race prep" budget). That TT3 car progressed greatly the last 2 years, winning 13 of 15 NASA TT events in 2013 and all of the TT events we entered in 2014, while securing the Regional TT3 championships both years by huge margins (with the maximum possible 800 class points). We relearned the importance of tires (width and compound) in TT, the value of proper testing, where to spend money on suspension, and of course we experimented with aero.


At Vorshlag, when we purchase "shop car" it has always been to develop new parts for that chassis then to go prove those parts in competition. We usually only keep a development car for one or two years, jumping around from different makes and models that have ranged from BMWs, Mitsubishis, Subarus, Mazdas, Chevys, Fords and more. Running the same red Mustang four seasons in a row has somehow made us into a "Mustang shop" in many people's eyes, but Vorshlag is more than that - we make suspension products for over 24 different makes/models and prepare and build race-oriented cars for many motorsports venues, including autocross, HPDE, TT, Club Racing, Pikes Peak, drag race, rallycross, and even top speed competitions.


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This pair of Subarus we have worked on aren't track cars. Left one is made for running Bonneville, the other for Pikes Peak


We hope this new build will show some of the variety of cars we work on, across all budgets, and show off some of the fabrication and race prep skills our crew excels at. Of course we are known for LS1 swaps into BMWs (E30, E36, E46, Z3 - see below) and we have Alpha Builds (development projects for future kits) for the Miata NB chassis and Scion FR-S/Subaru BRZ as well. Sadly, project DANGER ZONE won't be getting LS1 V8 powered swap, but it will make good power for it's class.


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A lot of people that see us at the track or read our build thread think "These Vorshlag guys spend a lot of money!", but the reality is we build our cars to run on a tighter budget than you might think. How did we stay on sticker sets of Hoosier A6s in 2013 and 2014? We won all of them, except for 1 set purchased at the beginning of the 2013 season. Our service shop also has experienced mechanics and fabricators who do all of the work on our cars between paying customer work - so we have the manpower, tools and skills, but not always the big bags of cash. We kept the engine bone stock on our TT3 car because it was easier for us to do suspension and aero mods than "purchasing horsepower" (we don't build or tune motors here). We also have two guys in the front office that are crew chiefs on outside race teams, and everyone that works here is a racer with regular motorsports experience, track side and/or behind the wheel. So a lot of times we build the things that might seem "expensive" to others, but are really just hand built items that come from hard work and experience - which can often be worth more than just throwing money at a race car.




We have done some very low budget builds, too. In late 2009 we wanted to try our hand at a budget-restricted magazine shootout, so we jumped into the Grassroots Motorsports sponsored $20XX Challenge. This is an annual 2-day competition event with 3 differing categories: autocross, drag race, and concours. You have roughly two grand to spend on the car and parts, plus a rigid set of rules to go by. With an all-volunteer crew (15 people helped put in 1200+ man hours!) we built a BMW E30 in my home garage with a truck LS-series V8 and ran it in the the GRM $2010 Challenge (as in: we spent less than $2010). We did fairly well that first year, learned a LOT by going to that event, recognized what mattered most by watching the winners, and came back in 2011 and won the whole thing. Lots of people fell in love with that car - whether it was the home built wide body, the nasty little V8 under hood, the BMW Art Car inspired graphics for 2011, or the extensive custom fabrication work done throughout the car to keep the parts budget low.


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I also ran our little GRM E30 in NASA TTU class where it fit with the power to weight ratio it ended up with, and had a blast there as well. After a few upgrades it was actually a better track car than an autocross car, funny enough. We cleaned it up, added a splitter, added some good looking 18x11" CCW wheels and sold that car for $18 grand... so sometimes your budget builds DO pay off after all!




Our very first NASA TT car was the TTU BMW E36 LS1 shown above, and it set an overall TT track record in its debut event way back in 2008. After that car left our stable we had a couple of other autocross cars that we ran briefly in TT lettered classes as well. My blue 2001 BMW E46 330 coupe (below left) was built initially around SCCA's DSP autocross class, flared with big 285s under all four corners, but it proved to be a MUCH better track car in TTD. It was run exactly one time and set a TTD record in the process. Same went for our STU autocross prepped 1997 BMW M3, which set a TTC record in one outing without any considerations made for track use.


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These two Bimmers were initially built as SCCA autocross cars but ran briefly - and won - in NASA TT lettered classes


Before This Our 2015 Race Season Looked... Bleak!


After the last two successful seasons running our Mustang in NASA TT3 and a couple of other series, this car was tidied up for SEMA with new flares, new paint, and new aero. We ran it at the Optima Challenge after SEMA, then when we came back home in November it went up for sale. The car looks so perfect right now that nobody here will let me take it out on track. They think I'll bang up the bodywork or paint... and with as wild as I drive, they are probably right. It now sits to await its new buyer, untouched and undriven.


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A major shop upgrade + new machines and equipment + extended SEMA/Optima trip all cost a lot of money


We just moved into a new shop that is twice as big as our old place, and did construction here for 6 weeks before we moved. The move happened 2 days before we went to SEMA, which was a 10 day trip for almost everyone here at Vorshlag. The pair of CNC machines arrived a month later. So needless to say, a lot of money was spent on the pre-SEMA car work, the move, construction and equipment of late. My "its a done deal" buyer for the Mustang fell through right before SEMA, too. All of that combined put a serious dent in my personal 2015 racing budget!


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There's a whole program of cars I was hoping to kick off with a shop built BMW E46 with a BIG nasty LS1 motor planned, and I've got 3 more chassis sitting in my home shop along with this E46, awaiting this turn-key race car program to start. But getting the drivetrain parts and wheels alone is going to take about $20K in cash, which seems to be missing at the moment, heh. So this project is delayed a bit while we get our CNC machines up and running and finish the construction at the new shop, so that meant no Vorshlag team car would be on track for at least 6 months. Sucks.


In Texas we race dang near year round. We did some track testing with the new S550 Mustang as recently as this December and there are NASA and SCCA road course events we need to hit in January and February, so there's no "off season" to complete any big build. Even if we kicked off the E46 build TODAY it wouldn't be on track until May or June. That's the majority of our Texas race season, and NASA Nationals West is in August. Long story short: We're out of time, and need to make a quick, low budget race car to be able to make the 2015 NASA race season.


continued below

Edited by Guest

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continued from above


I had all but written off racing at all in 2015, but as luck would have it, something came up that was too good to be true. Tomorrow I am picking up a semi-finished race car that will be our new "quick build" race car project. Until we fix a few things, and do a track test, I'm keeping "identities withheld to protect the innocent", so the make and model of the car are under wraps. It will be prepped and stored off site in a secret skunkworks facility...


NASA Time Trial Classing - A Brief Summary


This next bit might be confusing, but I'll be quick. So NASA Time Trial series rules are nearly identical to the Super Touring (ST) wheel to wheel club racing ruleset, without a lot of the safety requirements. Those two series' subsets of classes have a lot of common competition rules but with two distinctly different main philosophies. The "Lettered Classes" (TTB/TTC/TTD/TTE/TTF) are set-up where every car model gets assigned a "base class" then you get 19 points per class to use for "mods", which could be added tire width, aftermarket springs, aero tricks, various tire compounds have differing points values, motor upgrades, etc. If you modify the car beyond your allocated 19 points the car bumps up a class (like from TTD to TTC), and you get another 19 points to use in that class.


NASA Time Trial Rules: http://www.nasa-tt.com/rules



We bought the Vorshlag shop TTB, TTE and TTU cars to a NASA event once and ran them all. That was a hectic day...


These classes also each have their own minimum weight to power ratio that you cannot exceed even if your points expenditure is on lowering weight or horsepower additions, and each base classing includes a "base weight" you start with. If you want to run lighter than the base weight, it costs you points. If you want to run more tire than the base class tire, points. Some base classing also come with either a 7 or 14 point penalty, too (one star or two stars).


Each competition letter class has an assigned a minimum “Adjusted Weight/Power Ratio”. Regardless of how many points a car has, or which base class it begins in, it may not exceed the minimum “Adjusted Weight/Power Ratio” for its competition class. We will have to play with weights or power levels to stick with the limit for the class we're choosing, which could be one of the following:

  • TTB 10.50:1 (10.5 pounds per dyno measured wheel horsepower)
  • TTC 12.00:1
  • TTD 14.25:1
  • TTE 16.50:1
  • TTF 19.50:1

In the past 8 years I've competed in TTU, TT2, TT3, TTA (now gone), TTB, TTC, and TTD - and this car might be in one of those classes. Each letter class is also has an assigned "base tire width", regardless of what the OEM tire is. That list is below. Note: TTG and TTH (shown below) only exist for base classing, but these two classes are not acknowledged in TT competition. You have to class up to at least TTE, the slowest class allowed to run, for safety and "speed difference" reasons. With TTU and TT1 cars on the same track it would be a miracle if they didn't catch the TTG/TTH cars in the first lap, heh. Look up the cars classed in TTH and you will see what I mean - S-L-O-W!


TTB: 265mm, TTC: 255mm, TTD: 245mm, TTE: 235mm, TTF: 215mm, TTG: 195mm, TTH: 175mm


Here as is small sample of typical base class listings I looked up.

  • BMW 330 ('01-'06) (factory 225hp models)... base class TTE... minimum weight 3285 lbs... Base tire is 235mm, power to weight limit is 16.5:1. You have 19 to play with before bumping up a class and could dyno a maximum 199 whp at the minimum weight shown (with driver).
  • Ford Mustang GT ('05-'06)... base class TTD**... minimum weight 3450 lbs... Base tire 245mm. power to weight limit is 14.25:1. Two stars (-14 penalty) means you only have 5 points to play with before bumping up a class and could dyno a maximum 242 whp running at the minimum weight shown (with driver).
  • Mazda RX-8 (R3 model) ('09-'11) ... base class TTC... minimum weight 3045 lbs... Base tire 255mm, power to weight limit is 12:1. You have 19 to play with before bumping up a class and could dyno a maximum 253 whp at the minimum weight shown (with driver).


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The inherently faster and less rules encumbered "Numbered classes" (TT1/TT2/TT3) are different, since there are no longer "points" and modifications are almost completely "free". The power to weight ratio is what dictates which class you end up in (1/2/3/U). Many modern sports cars are so fast in stock form they get a base classing in TT1/2/3, and can't play the letter class games. There are "modifiers" to the TT1/2/3 power to weight ratio for major mods like: non-DOT racing slicks, sequential transmissions, AWD, tube frame chassis, and other major changes like that.


TT3 is unique in that any non-base trim level OEM aero mods cost you a big +0.4 modifier penalty on your power to weight limit (we took that in our Mustang build, for example), but aero mods are free in TT1 and TT2. TTU is the "Unlimited" class for NASA TT as well - you can run it as light and as powerful as you want, so long as it meets safety rules and has bodywork over the wheels (NASA eschews all open wheeled race cars).




That was a brief summary only, and I hope that made sense. We wrote this basic primer on NASA TT back in 2008, and of course the TT rules are linked above.


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We like making track cars fly - using non-stock aero tricks helps in Numbered Classes, but costs "lots of points" in Lettered Classes


We weighed the options for our TT3 Mustang early on and decided to take the "non-stock aero" penalty (running a massive wing out back and big splitter/ducted hood up front), maxed out the power to weight ratio (running at 3802 pounds to keep power at 433 whp peak, off of an adjusted 8.8:1 pounds per horsepower ratio), and ran the biggest, stickiest tires made by Hoosier (335F/345R Hoosier A6). On that car we realized in late 2012 that a softer tire compounds (A6) would allow us to get our fastest lap in the first two laps, before the front of the field tends to catch the back markers, which usually ensured a traffic free lap. That matters. We also noted the wider we went on tires (we started at 265, then went to 275, 305, 315, 335 and 345) the faster the car got. The added areo helped the car in high speed corners, of course, but also seemed to make braking better as well. We hope to apply some of this experience on our new TT car here, which is almost old enough to qualify as a vintage car, but spend less than 1/10th the budget. Will it work?? Are we delusional or genius?? You shall soon see...


Maximum Effect from Minimal Investment


This time we're NOT starting with a $40,000 brand new car, we're starting with an aging 24 year old... well.... beater. This car was purchased by the previous owner for $3000, and then he sold the interior bits and some other discarded parts and recouped $1000 of that, so it was s cheap starting point ($2K!). He then semi-prepped it for TT use but got busy with other projects and he suddenly wanted it gone - so it will soon come to our "secret offsite shop" to knock out the repairs and finish race preparations in the next 4 weeks.


Why did we choose this car? Well it happens to be "base classed" particularly well, and once people who know TT classes see where it ends up they might cry foul - but is has been classed there for many years and I've been waiting for someone to build one. We will document all of the modifications we do openly, show all testing performed looking for every ounce of speed, and post any race wins or losses along the way. Like we tend to do with all of our builds, we will be pouring over the rules looking for the optimum modifications allowed, and with several 25+ year veterans of amateur and pro racing working at Vorshlag, we know how read rules and seek out the most advantages possible.


"Rulebook Research" and bench racing is part of the fun of building a new race car, for us, and we've probably spent over 25 hours so far just looking at the "free" mods allowed in TT. We have run countless permutations allocating every point in the class (it isn't going to jump up a class), and going over every tire width/compound option, but there are still many unknowns in this build. Will an aero trick worth two points be worth more than a cat-back exhaust? We'll test that. What about this +10 point compound narrow tire vs a much wider +2 point tire? Testing it. Can it meet the power-to-weight limit? We'll dyno test the car early and often through the build.


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Of course it wouldn't be a Vorshlag build without digital scale pics; we will weigh EVERYTHING we touch. A lot of the interior has already been removed (its 400 pounds under the "base weight", so it will be getting some serious ballast added along with my 200 pound body) and nearly 50 pounds of drivetrain mass has been removed (100% legally), so the bone stock OEM motor is pretty "peppy". Look forward to lots of tech in this build thread which you might enjoy reading - or enjoy applying to your own track build.


If You're Not First You're Last


That Ricky Bobby logic above is going to apply here. As with our most recent TT build, pushing the limits but keeping it 100% legal is our goal for this project, so we won't be satisfied with anything other than a dominant performance and squeaky clean results in after-race inspections. We want to set ALL of the track records, win ALL of the trophies, get ALL of the points, and take home ALL of the contingency tires ... we basically want to swoop into a class we've not run before, act like a school yard bully and take all of the lunch money!


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We will be adding a roll cage and fire system, but that's not going to be shown as part of the TT "race prep budget"


Total build budget for this build for the 2015 season we are shooting for is $7500, all-in with initial purchase price + parts. That's not a lot of money for what we think we can pull off with this car, and what we predict the lap times will be (shooting for 6-8 seconds a lap slower than our TT3 records). We will continually be upgrading the car all season, as shop time and budget permits, and it will have proper safety gear (full cage, fire system, nets) very quickly. Who knows - it might even become legal for the mating ST class?


Tune in next time to see if we managed to win our first TT race or failed in epic fashion - either way, it will be entertaining! I will go back after the January NASA race coverage and show the initial 4 week build-up, any pre-race testing, and all of that. I also reserve the right to delete this thread and disavow all knowledge of it if the results are dismal.


What's Next + Vorshlag 2015 Race Schedule


These are the Time Trial and other competition events we want to enter with this car in 2015:


  • January 17-18 - NASA @ MSR-Houston Clockwise
  • January 17-18 - SCCA Club Trials @ MSR-Cresson (GRR! Why do they book the same weekends!?!)
  • February 14-15 - SCCA Club Trials @ TWS
  • March 14-15 - NASA @ MSR-Cresson
  • March 22 - Goodguys AAS at TMS (200 treadwear)
  • March 28-29 - USCA @ TMS (200 treadwear)
  • April 25-26 - NASA @ TWS
  • June 13-14 - NASA @ Hallett Summer Shootout
  • July 31-Aug 2 - NASA @ Laguna Seca - Western States Championships
  • September 4-6 - NASA @ VIR - Eastern States Championships
  • September 26-27 - NASA @ MSR-Houston Counter-Clockwise
  • October 17-18 - NASA @ "TBA" (???)
  • November - NASA @ "TBA" (probably ECR)


The main goal is to hit all of the NASA Texas events, and while the Laguna Seca "NASA Nationals West" event isn't that likely for us, "NASA Nationals East" at VIR might be in the cards. Right now we have only FOUR weeks until our first NASA race (we will skip SCCA for NASA, you double-booking dingbats), so its going to be a thrash to get it prepped for track use in less than 30 days! Our shop is very booked with suspension and race prep work, so I will work on it after hours if need be to get it done. Sleep is for the dead!


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Our fab shop just took this street car and turned it into an ST3 prepped race car - cage, wiring, fire systems, aero - in 6 weeks


This is going to a gutted/stripped car with NO compromises for street use at all, which we believe gives us the best chance for success. Daily driven cars haven't won many (any?) TT national championships with NASA in a while. This car has some great prep by the previous owner but it still needs some basic upgrades before it is fully track ready. We need to swap out the radiator for a racing-duty version, add an oil cooler, build in some major front brake ducting, install a proper racing seat (have one sitting in the lobby that I will steal), bolt in some harnesses and wrap them around a 4-point roll bar (initially; cage will be done hopefully by the February event). It also needs tires, a new windshield and a few other small repairs. Again, this is a CHEAP car to start with but when we're done its going to be embarrassingly quick on track. Cheap and Quick!


My final reason for building and racing this car in 2015 is - I'm a degenerate racing junkie, and I was clawing my eyes out thinking I was going to miss the next race season. Sure, I'm bummed that we cannot have the TT1 car built in time to run with NASA this year, so this was my only possible racing option. But I figured that running in a quarter century old beater has to be more fun than NOT racing anything at all, right?


What's in a Name?


We're going to be focusing exclusively on The Things That Matter, so there will be very little time spent on cosmetic improvements or other frivolous upgrades. But of course we do have a vinyl plotter, and a big part of running this car is MARKETING for Vorshlag, so we will throw some simple graphics on the car. They may be based on the Martini stripes on the Porsche 918 shown below (substituted with Vorshlag's Red/Black/Silver colors). We're trying to show that we can make anything fast and win, even aging 1980s era cars that have been mostly forgotten.


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“Something, something, danger zone! I know. I’m not even trying anymore.” - Sterling Archer


We've come up with a project name (gotta call it something other than "Broke Ass, Last Minute Backup Racing Plan") which has some obscure references to the 1980s, when this particular car was designed. After about 3 minutes of brainstorming I overruled everyone with taste and picked Project (

), which might make more sense when we get this thing on track. We tossed around some ideas to get there, like: the fact that this car designed in the 1980s, it may or may not have been on a cheesy 80's detective show called Miami Vice, which led us to the cars featured in Grand Theft:Auto Vice City, which inevitably led us to the last season of ARCHER season 5: Vice. That's only one missing step to tie into Kevin Bacon, I think. And who doesn't like Archer? Think of all the quotes I can use in my write-ups! This car would fit in well that TV series, if we added an in-dash mini-bar.


...and THAT'S how you get ants...


Other than those obscure hints, I'm keeping my lips sealed. The car will be built at a secret location (AJ Foyt's basement), so no matter what you think see in the Vorshlag shop, I won't reveal this dirty little secret until after Jan 17th. I will be posting more clues on the Vorshlag Facebook page, so keep an eye out there.


Until next time,

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Terry, are you too tall for a Miata?

Is it a convertible? (4 point roll bar now, cage later)

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Terry, are you too tall for a Miata?

Is it a convertible? (4 point roll bar now, cage later)


I have both owned and raced Miatas, and can fit in one with a custom seat... but at 6'3" with a stock seat, this is the result, below.




Broomstick test FAIL!

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Project Update for December 29th, 2014: This is an unexpected update - I'm going to break "radio silence" early because too many of you have guessed the car we are building before it's first race. Many of the guesses were hilarious and infinitely entertaining, and some of them were pretty good ideas for TT builds. More importantly this little project got some engagement and feedback. I'm always looking for feedback and comments, in case you have a better idea or way to do something, so keep it up! Now let's get to the answers to "The What and the Why" in this update.


Lucky guesses and True Detectives


Here were the initial clues I put in the first post, then some follow up clues on social media and various replies to questions and guesses on the forums. The clues became more specific as more folks chimed in with better ideas and guesses. If they gave their reasoning in their replies I would often answer yes or no, which led to more clues over the past few weeks.


  • It's not a Mustang
  • It's nearly 25 years old (so roughly a 1991 or 1992 model)
  • It's a chassis designed in the 1980s + something related to Miami Vice?
  • It does not have an LSx V8 in it, but it will be run with the factory installed engine
  • Worth about $3000 nowadays (in poor condition!), when purchased right
  • Not a turbo nor a 4 cylinder, and definitely not Front Wheel Drive
  • I stated that we would be racing on a tire 30mm smaller than the OEM size
  • I drove through Madisonville, Texas on the way to pick up the car from Dallas (hence a lot of guesses that it was in Houston)
  • After picking the car up I said it had a flywheel/clutch 50 pounds lighter than stock, and spun the tires through the 1st three gears
  • I hinted that I had possibly owned one of these cars before, and towards the end I said it was domestically produced
  • Lastly I said I worked "under the bonnet" one day last week, but then admitted not everyone calls it that but it was "more than just a hood"


All of these things were 100% true. The "Danger Zone" name was the only red herring, heh. That last clue was what triggered an avalanche of correct guesses. Jason Newman was the first to guess correctly - and he knew he was right a week before anyone else - with only about half the clues. That guess gets him a free Vorshlag T-shirt! Several others guessed "C4" along the way as well.


My Past Was Also A Hint


It helped that Jason knew more about me than most - he was a racing friend from college, when I raced in and helped run the largest collegiate sports car club in the country, the Texas A&M Sports Car Club. This was a club with over 150 members when I was there and we had one of the best autocross sites in the country - an old air force base that the school owned (Riverside Annex).


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Left: My 1994 LT1 6-spd Corvette Z07. Right: One of three V8 1992 Camaro 1LE/B4Cs (ex-pursuit) I owned


We set up huge autocrosess there, joining multiple runways at times. We also had lots of fun at nearby Texas World Speedway (TWS) running annual time trial events we called Aggiecross. This little college club was holding Time Trials back in the late 1980s, which didn't happen in NASA for decades. A lot of us worked at TWS while we were in school, and when we worked corners for PCA HPDE events we got free track time in our clunky, broke-ass student cars as well.


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Left: My ex-pursuit 1987 Mustang LX 5.0 was one of 6 Foxes I've owned. Right: Amy's 92 Mustang GT and my 1969 Mustang (C Prepared)


During my time racing with TAMSCC, both during college and after, I ran in a variety of cars. Since I was the proverbial "starving student" while in school many of these cars were crappy and cheap, but most of them still V8 powered and RWD. When I met Amy she had an 86 RX7 but once she raced in some of my cars she jumped to Mustangs and then Firebirds. Between us we've owned about 16 pony cars (Camaros and Mustangs) of various years, from 1969 through 2013 models. Two years after graduating I landed my second post-college job, which allowed me to commute from the same town (College Station). I was making great money in an oil field mechanical engineering position, and had extremely low living expenses. At one point there I owned 7 cars, including two project builds and an immaculate two year old Corvette (the white 1994 shown above).



Left: Amy's supercharged 1994 Trans Am on 17x11" HREs. Right: Her 1998 LS1 Formula


I tell you this because knowing what I used to own and race in my "Pre-Vorshlag Days" (nowadays I typically do NOT buy the cars I want but instead buy cars that need suspension development) helped clue in some old friends that knew this was to be a LOW budget build, but that somehow I knew it would be fast. Three amigos of mine were the ones to ferreted out the last few clues and got to the correct answer without question, before I confirmed it to them privately. These guys knew me too well, and were more racers from my days running with the TAMSCC: Matt Miller, John Scheier, and Doug Willie


Yet nobody correctly guessed that we'd keep it in TTC class.


Project Danger Zone Is...


So get on with the answer already! Sheesh...



This is the car we're building. It looks great, from this angle. This photo was staged perfectly - its a mess from any other angle!


This is it. What you are looking at is a 1992 Chevrolet Corvette 6-speed that is bone stock, except for being stripped of a nasty old interior. This is a base trim level car with the factory 5.7L "LT1" (Gen II) 300 hp iron block V8 and ZF S6-40 6-speed manual transmission. It has the strong Dana 44 rear axle assembly (not the Dana 36 that came in the early C4s and automatics). This particular car has 68K original miles and from the angle shown above doesn't look at all like a $2000 car. Regardless of how clean it looks now it was still a hot mess when purchased.


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The entire interior is gutted, even most of the dash. We will finish what was started and put the dash cap back on


I will go over the issues on this specific car as we chronicle the repairs and upgrades to it this season. The previous owner (Brian Matteucci) has done a lot of repairs and refurbishment, and even a couple upgrades but we still have a laundry list of safety updates to tackle, as well as a few performance mods to "max it out" for TTC class points. We are keeping the car legal for TTC class so there aren't a whole lot of "points" we can burn on upgrades, so the car will remain stock in many aspects. Luckily, a stock 1992 Corvette doesn't suck!


Why is the C4 Still A Worthwhile Track Rat?


To understand why we consider this 24 year old car still relevant, we need to look at how this car was designed and what it came with that was ahead of its time. Here is a brief look at the C4 generation Corvette, which was produced from 1984 to 1996.


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We're already getting to work on this 1992 Corvette at Vorshlag. Parts are ordered and it was detailed by yours truly


GM calls the Corvette chassis the Y-body and it has been produced from 1953-current in 7 distinct chassis generations (see the Corvette Wiki). The "C4" generation was designed in the early 1980s and was delayed a bit before launched as a 1984 model (there was no 1983 Corvette). This chassis was a huge leap in sophistication from the C3 chassis it replaced. None of the subsequent Y-body chassis were this revolutionary - C5, C6 and C7 all share design aspects of the C4 and are instead mostly refinements (yes, the C5 had some serious updates!). The C4 was the first "Billion Dollar Chassis" design in the history of automobiles - and it doesn't share anything with any other GM chassis, so there was nothing to be gained for another, mass produced chassis (exception: almost all engines developed in the Corvette make their way into the F-body chassis and others).


With fairly low production numbers each year this has got to be a "loss leader" for General Motors at only about $40,000 when this car was new in 1991. And now with 3 newer generations of Corvette following the C4, this chassis has bottomed out in resale value - its not old enough to be considered a classic but its not new enough to be worth a lot of money. Some year C4s can be had for next to nothing, and even the later C4s can be snatched up cheap if it has any issues (like this one) and made into a low buck race car faster and more sophisticated than 75% of the cars at any given NASA race weekend. And this 1992 model one of the best of the C4 generation.


Engines: The C4 had 4 major engine designs in its 13 year run (1984-1996), which began in 1984 model with the abysmal Cross Fire V8. This was a horrid, 205 hp, early attempt at a fuel injected V8 and a complete carryover from the outgoing 1982 C3 Corvette. The Crossfire L83 has ZERO redeeming qualities and was only used for one model year in the C4. Starting in 1985 was the 5.7L L98, better known as the Tuned Port Injected or "TPI" V8. These long runner intake equipped V8s had LOADS of low end torque but petered out above 4000 rpms. With aluminum heads this "Gen I" Small Block Chevy (SBC) made decent power for the early 1980s (230 hp then up to 250 hp) but stuck around far too long (through 1991 model).


This was followed by the revolutionary 300hp 5.7L "LT1" Gen-II V8 in 1992, considered the first new design in the Small Block Chevy's long history (hence the Generation II engine; the LS1 in 1997 was the Gen III). There's tons of data out there about this motor, of course. In 1996 there was a special edition version of this motor called the "LT4" made 330 hp. Lastly, during the middle of the C4 model run was the LT5 DOHC V8 that came in the ZR1 (1990-95, 385-405 hp), which was a technological marvel for its time but was quickly overshadowed by the all aluminum OHV V8 that came out in the C5 - the LS1.


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The Gen-II LT1 engine was unique in that it only lasted 5 model years, but it was also used in the 4th Gen F-body (1993-97 Camaro/Firebird) and the Caprice/Impala (1994-96 B-body) as well as one Cadillac (1994-96 Fleetwood). The reverse flow cooling was a big change but other than the bump to 10.5:1 compression ratio, produced very little benefit, and this "reverse" cooling style (heads cooled before block) was dropped in the Gen III LS1. The distributor (Optispark) is very unusual; it is driven by the camshaft and tucked behind the water pump. It is somewhat problematic and prone to water damage, but the later '95-96 "vented" style works better and aftermarket versions better still. The intake manifold is about as far from the TPI motors as you can get - it has larger but very short runners which produce a higher RPM range and a much flatter torque curve than the tractor motor curve of the TPI.


The Y-body LT1 always got 4-bolt main bearing caps (the other's all had 2-bolt mains), but the 1992 Corvette's LT1 is unique in one key way. The TPI motors (1985-1991) all used a crude form of Fuel Injection called batch fire port injection, and used a Mass Air Flow meter to meter incoming air into the engine. These early MAF designs used a circuit board that was in the airstream and were problematic from day one. The 1993-96 Y-body and 1993-97 F-body LT1/4 engines went to a more modern hot wire element MAF with the electronics housed outside of the airstream. But for the 1992 Corvette (and 1993 F-body) this new EFI system wasn't ready and for one model year only GM went with a speed density air metering system (no MAF). This uses Manifold Pressure Sensor along with a atmospheric pressure sensor to read incoming air. This lack of a MAF means a lack of a restriction in the airstream for that one year - and the 1992 model ran the strongest of all of the LT1s in stock form.


The manual transmissions used in the early C4s (1984-88 models) was a Doug Nash designed "4+3" transmission – a 4-speed manual coupled to an automatic overdrive on the top three gears. It was designed to improve fuel economy but was mostly a steaming pile of crap. For the 1989-96 model Y-bodies, GM went to the Germans and they offered up the S6-40, made by ZF. It is an unusual transmission and parts are hard to come by, and shops have popped up like ZFDoc that specialize in rebuilding these brutes. This trans is nicknamed the "ZF6" and is big, heavy and very strong, if a bit noisy. With 6 speeds and 2 overdrives (.75 in 5th and .50 in 6th), it made for excellent fuel economy. The Borg Warner/Tremec copied these overdrives for the later T56. With the ZF6 tall 2.68 first gear, the "black tag" version is rated to withstand 450+ ft lbs of torque (and is much stronger with a modern carbon synchro upgrade). To quiet the noises, GM used a heavy dual mass flywheel, which tips the scales at over 40 pounds. The clutch is also strong and the Dana 44 rear differential out back is also a brute. The limited slip unit in these 44s tends to last decades... and I hope so because we're not touching it. The halfshafts are big beefy aluminum tubular units with U-joints (cheap to replace!) instead of CV joints, and the driveshaft is built the same way.




The body is fairly aerodynamic (low height, low drag, small front area) and works well at high speeds. The body panels are made of fiberglass - which is good considering it has some chunks missing, and fiberglass is easy to repair. Some damned fool drove this car through a barbed wire fence back in its' checkered past, which damaged the front bumper cover and body panels on the left side. The driver's door was trashed but the replacement doesn't match the car's white paint well, so that will likely get repainted at some point. I will patch the fiberglass that is damaged myself and prime it for later repaint.


continued below

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continued from above


Where Did This Car Come From?


So about 3 years ago an old friend, Brian Matteucci, wanted to build a NASA Time Trial car. He was a long time autocrosser and former SCCA W2W Club Racer and watched what we were doing in NASA. He liked the cost-to-seat-time ratio of the TT series of classes, which was why we were in it as well. I helped him understand the NASA TT rules as well as the confusing TT classing formula and points classing system. We bench raced several builds over a few weeks and came up with the C4. That was no accident - because we had both raced these in the past. My history with Matteucci goes way back to about 1989, when he was a racer in the Texas A&M Sport Car club racing in a notchback 5.0L Mustang... I was about a year ahead of him and happened to be racing the same exact type of car.


We were competitors and friends through college, both helped create a new and popular autocross class called Super Street Mod in 1990 (we used this class to help push the SCCA to create Street Mod), and were roommates after college when we both worked at our first jobs in Houston as engineers. He and I both used to love digging through rule books looking for ringer cars and rules to exploit. After college we both autocrossed C4 Corvettes for a time - he was in a 1987 Z51 while I raced a 1994 Z07, both in SCCA's Super Stock class. When his 87 Corvette's fuel pump died on day 2 at Solo Nationals one year he co-drove my C4 - and hated it.



My 1994 Corvette Z07 running in Super Stock at Solo Nationals in 1998. It was on Hoosier DOTs but was otherwise bone stock


The differences between our cars was dramatic back then - at low speed autocrosses - but it was obvious to both of us that the LT1 was far superior to the TPI engines at higher speeds. Already owning a C5 Z06, when he suggested a letter class TT build 3 years ago I immediately suggested another Corvette, but one that was a 100% dedicated, no-compromise race car build. Jason and I here at Vorshlag had often talked about the TTC classing of the late C4, and after some discussion with Matteucci, he agreed that it had a lot of potential in this class. He went out and bought this mess for $3000, sold off the interior bits for $1000, and had a $2000 platform to build a TT lettered class car from.


During the next 2-1/2 years Matteucci proceeded to strip hundreds of pounds out of this car and replaced lots of broken OEM bits (24 years can take its toll on anything), while testing it at various autocross events along the way. He did this while he was very busy with work, building a new house and shop, building a chump car, and autocrossing his C5 Z06. In December 2014 he got to a good stopping point and I bought the car for a great price - along with a promise to let him co-drive the car with me in NASA TT. Amy and I did that last year and it was a good way to get us both out on track for less money spent - which fits this project well.


With our "Team Vorshlag" entry we can both drive the car for one entry fee, doubling the chances for a fast time (two sets of eyes and brains are better than one). Matteucci worked at Roush Engineering for several years, and while there was responsible for building and developing a fleet of Bonduraunt school cars when Ford was their supplier in the 2000s. He lived at the track for many months, driving these cars for hours every day, so he's no stranger to finding a good track set-up: he was paid by one of the biggest engineering/racing companies in the world to do just this.


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Left: The factory power steering cooler is a huge double-pass unit. Right: I pressure washed underneath to help find an oil leak


Last but not least, Matteucci was also the designer of our first three initial camber plate designs when he started Motor-Force Engineering back in 2002. We bought his company (and IP) back in early 2006 and several of the current Vorshlag camber plates can trace their roots back to his initial designs. Other than some manufacturing aspects and tweaks to materials and coatings, they are for the most part unchanged. So he has a long history with me and Vorshlag, whether he wants to admit it or not, heh. When I picked up the car on December 20th I gave him a bunch of Vorshlag swag, which was part of the deal with the car - he has to wear this stuff at the track, especially if he is the one who gets the wins!


TT Classing Looks Solid


So if you look at the NASA TT (and PT) classification for Corvettes something jumps out at you (go to page 20 of the TT rules) - most Corvettes either require a dyno test for an initial base classing (C1-C3) or are just shoved straight into TT1/2/3 numbered classes (C5-C7). The lone exception is the C4 generation, which has 5 separate letter class listings:


MODEL........................................BASE CLASS...... MIN WT

Corvette C4 ('85-'91)............................ TTD**......3223

Corvette C4 ('92-'96) (LT1)................ TTC*.......3203

Corvette C4 (LT4 option) (330 hp)...... TTC**......3350

Corvette GS ('96).................................. TTC**......3350

Corvette ZR-1 ('90-'95).......................... TTB*........3500


While the TTD entry for the 1984-1991 "TPI" Corvettes might look the most attractive place to start at first glance, the minimum weight is higher yet they make a lot less power (230-250 hp) than the LT1s. With two stars it is already -14 points out of 19 in TTD class, and strapped with TTD's 245mm base tire size, so it would be nearly impossible to stay in TTD class, meaning it would need a lot of work to be competitive in TTC. Of course upclassing adds 20 points to play with, so it might make the 12:1 power to weight ratio of TTC, with some dollars and points burned on engine upgrades. The two LT4 powered cars (all 1996 6-speed cars and the '96 Grand Sport) have an extra star (-14 points in class) and extra 150 pounds of minimum weight, but the only advantage being +30 hp over the LT1 it is not ideal (plus they are worth more money used). Likewise the ZR1 has +300 pounds more minimum weight (and boy were they heavy!) and its up a class (TTB) and has one star (-7), plus these are somewhat rare and pricey, and expensive to maintain and upgrade. Yuck.


So the lighter, rugged and simple 1992-1996 LT1 cars are really the best bet, in my mind. TTC seems like an odd place to class the 1992-96 LT1 Corvette - and it might well be, but it is pretty old and I doubt many (any?) have been competitively run in NASA TT or PT. We shall soon find out if this base class makes sense, because that's where we are going to run it.


TTC 1992 Corvette Build Basics


While several folks guessed we would be building a "C4 in TTB", nobody guessed the TTC angle. And why would you? With the base classing of TTC* we only have 14 points to play with in class, so how could it be as "fast" as I predicted? For one, it doesn't need any points spent on power mods to meet the max power-to-weight ratio, as it will easily make the 12:1 limit for the class. So we save points there. How do I know? I owned a nearly identical 1994 Corvette that I had dyno'd on a modern DynoJet, where it made 277 whp in bone stock form, back in 1996 (these cars were a hair under-rated at "300 hp" crank). Another TAMSCC racer (Mike Mclure) owned a 1996 LT4 Corvette and dyno'd it at 308 whp the same day on the same dyno (also under-rated by the factory). If you know your dyno numbers, you will see that the LT4 makes almost exactly what a stock LS1 makes in a C5 (~310 whp), and the LT1 just a little bit down on that.


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Left: The 12" front brakes are adequate but can be upgraded to 13" rotors "for free" (no points). Right: The ABS system is ahead of its time


The factory brakes are also ahead of other cars from this era and not much if any off of the C5. GM developed its best ABS systems on the Y-body and this 1992 model has one of the best of the generation. And while the 12" diameter front brakes seem a little wimpy on the Base Trim Model, which this car has, they aren't total junk. The calipers are twin piston floating PBR units, a cast aluminum design used on the Y-body, F-body, and even the SN95 Mustang Cobra, to name a few. We have found a way in digging through the rules and Base Trim Level of the 1992-96 Corvettes to upgrade the discs to thicker, 13" diameter discs for zero points (more on that soon), so that saves us points and only costs a few dollars.


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We will show better suspension pics in the next update, but these will do for now


Suspension is very advanced for the time period, and better than what many of us race with on brand new cars from today. Forged aluminum uprights at both ends pivot on double A-arms up front and a multi-link rear IRS. Both ends are sprung by a composite transverse leaf with factory monotube Bilstein dampers. Other than some freshening and an alignment we're going to leave that pretty much alone.


Last up is the tires. The late C4 was designed to house massive wheels and tires (factory used 17x9.5" on almost all packages and up to 17x11" out back). While we won't be making flares to house big wheels, which is kind of one of our "go to" first mods, we will blow almost ALL of the available class points on tires (more on that next time).


Why not bump up to TTB? Sure, we think this car could be just as competitive there at this class' more aggressive 10.5:1 pounds-per-hp ratio, but it would allow for a lot more mods, and that costs $$. The goal of this is to keep costs down, but with +20 more points to play with after upclassing we could easily spend an extra $10,000 chasing down the points and the top cars in TTB (S2000 + E46 M3). While this would be fun, that's not our goal for the 2015 season. We want to instead focus on the "free mods" that TT allows as well as spend our precious 13 points as wisely as we can, as well as show some of our best "race prep" and safety upgrades - that are the same for virtually all classes.


In the next post we will sow our first few mods - brakes and shocks - that are both zero point upgrades. We will also show our first point mod and show the behind the scenes upgrades and race prep.


What's Next?


I always close my build thread posts with a teaser for the next entry. Well we haven't done much to the car yet, so there's still a lot of track prep to knock out. We did order OEM replacement brake parts and shocks, all zero point upgrades which I will explain in my next post. The next biggest things the C4 needs before the first event are all safety related.


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In early 2014 our crew here built the cage and did all of the fire/safety/lighting upgrades for a 1987 Corvette convertible that was initially run in Lemons and Chump but lately has been competing in WRL series endurance events (also known as - the Poorvette). We learned a lot working on that car that will apply to this TTC build, of course. One of the items we will replicate on our car is the roll cage, but due to time constraints (3 weeks to go!) before the first race we will only make the main hoop, harness bar and rear downbars (4 point roll bar) for now.


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We will go back and complete the full roll cage structure this car after the first event, to make everything safer (and to add some more ballast weight). Unlike this black 87, our 92 C4 has a roof - but its just a bolt-on targa panel, like all hardtop C4s. That removable roof panel makes it easier to build the cage and provides some aerodynamic advantages over the drop top, but the rear (glass) hatch main roof support structure will still be in the way and make this one a bit more challenging to build.


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Left: This is the seat we'll be using in the TTC car. Right: An adjustable seat back brace is visible in this pic


Another area that needs some attention fast is the seat mounting. The OEM seat that came with the car BROKE at an autocross event, which Matteucci warned me about ahead of time. We bought this Kirky 56700LW aluminum seat (see above left) for the Poorvette, but the driver wanted something different so we were stuck with it. This TTC4 project will get a lot of those cast away parts, some of which are brand new. Since the seat is a touch on the big side (17" width) we will make a poured foam seat insert, as well as a seat back brace tied to the cage (see above right)


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Due to the weird floor structure of the C4 chassis (some parts are composite and some are sheet metal), and some damage from a previous owner (aka: the Crack Head that tore up the interior and drove through the barbed wire fence), we need to repair and reinforce the floor areas. These cars are tricky to safely mount a racing seat into, as well as ballast plates, both of which we will need to do. The car is already 200 pounds under minimum weight (including a 200 pound driver) and that will only worsen as we (legally) replace OEM body panels and rear glass with lighter weight alternatives. We will run this car at the 3203 pound stated minimum weight and NOT burn points on running a lower weight. Running lighter might seem advantageous but we would have to lower the power output as well (the 12:1 ratio doesn't change for TTC class even if you burn points to "run lighter than minimum").


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Two zero-point mods Matteucci already added include the Moroso 20185 road race LT1 oil pan (allowed under TT rules, page 36), which at $288 includes more capacity, a Kicked-Out Sump and Trap Door Baffling for improved oil control, built-in Windage Screen and a port for an oil level sensor. The QuarterMaster 7.25" triple disc clutch ($599) and flywheel are also zero point mods (see page 36) and knocked nearly 50 pounds out of the drivetrain mass. It makes this little LT1 rev quite nicely and shift very well at speed - but driving it around at low speeds is a BITCH and it unlocks a LOT of transmission noise. Don't have accurate pics of these mods yet, but when we take them apart I will get better images and weights. I will include these "zero point" aftermarket part upgrades costs into our build budget, below.


Budget to Date


I don't like showing what I paid for cars, so for the purchase price shown is what Matteucci paid for the car three years ago (he bought it well!) - which was a running, full interior car but fairly rough inside when he got it. He cleaned it up a lot and I've cleaned it up further (spent about 8 hours detailing it this past weekend). On any OEM replacement parts we swap out I will show a "common street price" for what we use. Instead of showing labor costs I will show the logged hours spent on each task + material costs on anything we fabricate. The safety gear will be shown separately, as this is all entirely optional in a TT car, but still important to keep account of. The goal is to spend at or below $7500 for the car + performance upgrades + materials + one set of consumables.


Car Purchase: $3000

Recouped into budget: -$1000 for interior

Quarter master clutch: $599

Moroso oil pan: $288

Kirky racing seat: $0 (safety upgrade, $328 retail)

Total Spent so far: $2887


That's all for this time. I will post another update before the first race, January 17th at MSR-Houston, where we will debut the car in NASA's TTC class with me and Matteucci at the wheel. That's assuming everything goes smoothly! The next update will show some actual work being done besides my initial clean-up, and I will also lay out more of our game plan for the season, including which tires we plan to run with. They are 30mm smaller the stock size, but it will make sense why soon.



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fielding a one-asterix car that stays in base can be frustrating from a builder's standpoint, but can be rewarding from a driver's standpoint in the sense that "Well crap, can't change it so just gotta drive faster!!".


Will be keeping an eye on how this turns out should outrun my TTC/B car (depending on where A6s shake out and not ruining the drive-around streets either). Heberto - hope you've been busy this offseason tweaking you're the only hope for all of the rotary world

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Ken, as you know, there is still a lot that can be done with a few points, and even a lot that can be done with no points. Best is that by combining a few low point and no point mods, we can do some truly great things.

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Interested to see how you get around the +2 on the BTM brake rotor diameter...

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Interested to see how you get around the +2 on the BTM brake rotor diameter...



I'm going to be debuting my 2003 MINI Cooper S in TTC at MSR-H as well. I was hoping that Terry got something wrong in his interpretation of the rules, but he is spot on. This is a legal upgrade specific to the 92-96 LT1 powered base Corvette. The 1996 model came with the "Heavy Duty Brakes" as standard on the base model. So although they were an optional upgrade in 1992, they are legal under the updating/backdating rule because they were the standard brakes in a model of the model group listing and in the same generation. Great work maximizing your no point modifications, Terry!


I don't know how well my 1.6L, FWD, McPherson strut, brick of a car will do up against a V8 Corvette. Could there be any two cars as vastly different competing? I kinda feel like I'm bringing a knife to a gun fight. It should make for an interesting David vs. Goliath battle!



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This car versus the others you typically see in the class are going to have some different strengths and weaknesses. Going to be some "horses for courses" sorta phenomenons going on as certain tracks are going to highlight some sets of strengths and punish others differently. Then there's that whole driver thing to throw into the mix as well

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I owned a nearly identical 1994 Corvette that I had dyno'd on a modern DynoJet, where it made 277 whp in bone stock form, back in 1996 (these cars were a hair under-rated at "300 hp" crank).


We will run this car at the 3203 pound stated minimum weight and NOT burn points on running a lower weight. Running lighter might seem advantageous but we would have to lower the power output as well (the 12:1 ratio doesn't change for TTC class even if you burn points to "run lighter than minimum").



When I first looked at this, I wondered how you were staying at 12:1. Then I noticed you said you were running a 30mm smaller than stock tire. Stock is a 275, so you are running a 245. This means you can take a power modification +0.8. Thus your raw p/w can be be 11.2:1 and still be legal.


Any competitor that is following this thread take note: This is how you are competitive without over spending--look for things that give you an advantage and save money. A 245 tire costs less than a 275. You might give up a little mid-corner grip, but you can offset that by running more power down the straights.


Again, great job of maximizing the rules! I'm really starting to get excited about running TTC this year!



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I'm going to be debuting my 2003 MINI Cooper S in TTC at MSR-H as well. I was hoping that Terry got something wrong in his interpretation of the rules, but he is spot on. This is a legal upgrade specific to the 92-96 LT1 powered base Corvette. The 1996 model came with the "Heavy Duty Brakes" as standard on the base model. So although they were an optional upgrade in 1992, they are legal under the updating/backdating rule because they were the standard brakes in a model of the model group listing and in the same generation. Great work maximizing your no point modifications, Terry!


Yep, you know your Corvettes, my friend! That's the exact loophole we found - all 1996 models came with 13" brakes, even the BTM. And the listing is for non-LT4 "1992-1996 Corvettes".


Hopefully the brake parts will get here in time, otherwise we'll do the first event on the wimpy 12" stuff. Yuck!


I don't know how well my 1.6L, FWD, McPherson strut, brick of a car will do up against a V8 Corvette. Could there be any two cars as vastly different competing? I kinda feel like I'm bringing a knife to a gun fight. It should make for an interesting David vs. Goliath battle!



For sure, very different platforms, but very different weights, too. Should be a fun battle, as long as this 24 year old jalopy holds together!




We're thrashing on DANGER ZONE right now and I will update the Build Thread later today. Lots to do!

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Project Update for January 9th, 2015: The first stage of "initial race prep" for this project is getting down to the wire with the NASA race debut only ONE week away! Let's get caught up on the work we've been knocking on Project DANGER ZONE, our TTC class prepped 1992 Corvette. I had intended this to be a quick update, showing the initial stages of race prep, but I started writing and somehow this post spiraled out of control. It now includes some aero/drag reduction theory, the History of Iron and Steel, a good bit on roll cage tubing and design, some tire analysis, and other random tidbits of tech. If you get bored easily just skip down to the pictures and enjoy.


Safety First, Kids!


There are many Safety Upgrades we want to add to (or repair on) this Corvette during the 2015 season, which are the same for virtually any dedicated road race build. Unfortunately we were pressed for time and won't get them all done before the first race. The Safety list includes: a full roll cage, racing seat install, 6-point racing harness, window nets, full fire extinguisher system, secondary 2.5 pound fire bottle, tow hooks at both ends, tie-down hooks at both ends (for towing), replace the broken windshield, replace the rear hatch glass with Lexan or Plexiglass, and more. That's a lot of parts and work on the "Punch List", but as far as what's "required" for NASA Time Trial, that is much less. We also have some repairs and performance upgrades to tackle, too. We got almost nothing done over the holidays (short weeks, busy on customer cars) so let's see what we can get done in two weeks.


Windshield + Small Aero Improvements


This repair is really a safety upgrade, because you cannot race with a busted windshield. Before I bought the car from Matteucci he had warned me about this problem - it had a lot of big cracks on the passenger side and chunk missing where the OEM rear view mirror attached, with the cracks propagating into the driver's view. The upper right corner of the windshield trim and weatherstrip took a hit when a former owner (ie: The Crackhead) drove it through a barbed wire fence. Matteucci literally found a crack pipe (maybe a meth pipe) in the car after he bought it. So yea, now you understand part of why this was a $3000 running and driving car purchase.



Nasty, broken windshield and trashed weatherstripping has to be replaced


We discussed delaying the windshield replacement because when you install a roll cage it is ALWAYS easier (and often required) to get the front windshield out of the way to access and weld tubes along the front of the cage. In some cars with a fixed rear glass window, that is often removed as well. The cages we built in the two cars below required the windshield to be out. At left is an SCTA legal cage for 200+ mph use on the salt flats, which has more of a "Funny Car" drag racing cage (built per the rules). To weld in the the front tubing gussets requires windshield access. The one at right is a NASA ST3 legal Mustang the the dimple-die gussets and front corner tubes need windshield access - as does a proper paint job on any cage.


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We knew we wanted a roll cage in DANGER ZONE (to reduce the "zone of danger"), but with only 2 weeks of time build available after the short holiday weeks between Christmas and New years, and many other items that needed attention, meant only building a 4-point roll bar for this first race. Which meant the windshield didn't need to come out. But it was so cracked that it would never pass tech, so it had to be replaced. And when we go back and finish the full cage, out it will come again!


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We called our buddies at Titan Auto Glass and they extracted the old and busted and installed the new hotness. There are normally several windshield choices for most cars, varying in price, but for 24 year old Corvettes there was one - and it was a tick pricy at $260 installed. But hey, can't race with a busted windshield. Going to Lexan is an option but there are more downsides (more costly, harder to install, easily scratched, difficult to use wipers with them, more easily nicked by rocks or tire klag) than upsides (slight weight savings). A two layer, laminated, glass OEM style windshield is preferred by many racers when they have a choice.


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The OEM windshield surround rubber weather stripping was a total mess (above right). Matteucci had cut away the bits around the A-pillars when he gutted the interior and the top bit was destroyed by the barbed wire. The crackhead former owner had filled in the missing chunk in the rubber seal with SHOE GOO, and that had to be chiseled away (thanks Titan!).


I wasn't about to put this mangled mess of rubber seals back on, but we needed the top bit of rubber to seal the targa roof panel smoothly along the top of the windshield and I also wanted the seals back in place along the edge of the windshield at the A-pillar. This should help smooth the airflow in a high payoff "Green Zone" of potential drag reduction - the edges of the windshield. Read this NASA Speed News article called "Getting Into The Zones" (page 60) written by aero guru Neil Roberts (also read his ThinkFAST Engineering blog for more great articles!) and that will make more sense.




A smooth, new set of weather stripping should help aid the transition from the edge of the windshield (sides and top), reducing drag. We are looking to reduce drag in ALL of the Green areas (again, read Neil's article) on this car, and do so legally. We cannot run NASA events with the windows up, so the door window openings have to stay. We have tried to read the rules to say otherwise, but rule 7.2 of the NASA TT rules is pretty clear:


7.2 Front driver and passenger side fixed/Lexan windows are specifically not permitted unless they are factory installed during the manufacturing of the vehicle. Both front side windows must otherwise be in the down position while on track."


Running the windows UP would be a decrease in drag but it is not allowed in virtually any form of road racing, for safety reasons (easier extraction after a crash). Some drag racing classes and high speed events like Bonneville do allow for side windows, so the silver Subaru we're building the cage for above is getting a full Lexan window package (4 side windows + front and rear windscreens).


Why Terry Needs A Roll Cage


There isn't any additional safety requirements in NASA Time Trial groups than what is called for in HPDE run groups: a Snell SA2010 rated helmet and OEM seat belt, plus a roll bar for convertibles. There isn't supposed to be wheel to wheel contact in TT, but we are running for times and competing for contingency prizes, and many TT racers take it pretty seriously. I won six sets of Hoosier race tires racing in NASA TT3 class in 2014, and these were BIG tires that cost $1710 a set, so there is some decent swag on the line. When you are chasing a TT win you often push the limits and do stupid stuff...



Crap like this


My personal safety record, for the amount of laps I've driven on track, was pretty damned good up until 2014. In 27 years of running on road courses I only had a couple of "offs" that were worth mentioning. I de-beaded a couple of tires in a high speed off at TWS in the late 1980s that curled my hair a bit. A number of times I've had a quick "off and on" that bent a splitter or packed a grill with grass, sure. The stock brake pads came apart and I left Turn 7 at ECR at 90+ mph in 2013 in a stock '13 Mustang. But by far my most memorable off-track experience happened in 2014 (shown above).



After the crash I began wearing a HANS device and fire suit to complement the FIA halo seat, 6-poiont harnesses and roll bar in our TT3 Mustang


I briefly mentioned this in my first post, but it was a pretty spooky incident and I figured it might explain my "overkill" safety requirements for this TT build. After losing brakes at at Road Atlanta at a Global Time Attack event in May 2014, I went off the end of Turn 10A at 150mph, through the gravel trap, and took a big vertical hit coming out of a trap. I got hurt but the car barely took a scratch (splitter came off, was repaired and reinstalled and back on track 2 weeks later, but not with me driving). Even though I had a proper FIA halo seat, good harnesses, and a good roll bar, I wasn't wearing a HANS device. We think this might be why I fractured a vertebrae in my back and broke a rib. After this incident I was in a lot of pain, wearing a back brace for 2 months, and not racing.


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Having gone through the crash scenario many times and analyzing frame-by-frame pictures of the crash since, the injury seems to come down to too much "arching" of my back in the impact that broke these bones. A properly worn HANS device would have likely prevented this injury. The "off" happened because I ran out of brake pads, and had been ignoring measured brake caliper temp data of 490°F+ for months. I'm not going to make those series of mistakes again, and I also vowed in 2014 to start racing with better personal safety gear. I was setting a bad example and I needed to do better.


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So obviously, after this back-breaking scare I'm taking my safety on track a lot more seriously. I've starting using a HANS device (still haven't picked my favorite model after trying 4 different brands - and I'm about to try the brand new Schroth HANS design, since we are a dealer) and an FIA 3-layer driving suit in all TT events. I am also wearing my harnesses TIGHTER and keeping a much closer eye on things like brake fluid temps and brake pad material depth, so this scenario of failures never happens again.


Roll Cage Is Safety More Than Performance



The steel frame structure of the C4 Corvette. This is a 1984 model


After the personal safety gear, the next most important safety aspect of any race car is the roll cage. This structure is helpful to make the chassis more rigid, sure, but it is there mostly to prevent bodily injury in many types of crashes and "offs". These include single car off track frontal collisions with a barrier (somewhat common), a roll-over crash (very rare), or any car-to-car contact (more common). While a roll cage wouldn't have helped me in my gravel trap "jump" incident at all, there are other types of crashes where it could save your life - and do so more effectively than the basic 4-point roll bars we have used in my last 3 personal race car builds. I own a shop that builds roll cages and haven't had one in my own cars in 6 years... that's crazy.


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Corvette roll cages are tricky. All Corvette chassis generations (C1-C7) have a strong metal frame (steel frames through the C5, with aluminum frames for C6 Z06 and all C7s) with a composite body attached to it. Adding a roll cage to these cars has some extra challenges, since you need to cut away fiberglass to access the metal frames, but its nothing we haven't done before.


As I spoke about above, TIME is not on our side for this first NASA event, so we had to cut back on the roll cage plans for the maiden voyage. We could have bought a second-hand 4-point roll bar but it would never fit as tight to the roof structure in this gutted car (they are usually made for full interior cars).


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Frame differences on the 1984-1991 (left) and 1992-1996 (right) C4 Corvettes


Quick sidebar: the C4 Corvette had major changes to the suspension (1989) and even to the frame (1992), along with major changes to the drivetrain (1989 for ZF and 1992 for LT1), front crossmember, and transmission tunnel over the 13 year long model run. The two "body shop spec" images above show the changes to the frame at the 1992 model year, and we've noticed a lot of other differences to the interior fiberglass structure.




Last year we caged and safety prepped a 1987 Corvette convertible (shown above) and after looking at pictures of both that and our 1992, it had a lot of structural differences at the tunnel, firewall, and rear bulkhead (behind the front seats), not to mention the dash, body, and other obvious differences. The frame was also different in some key areas. We are using the NASA CCR for cage design specifications on our car, but the black 87 used a mix of NASA, WRL, Lemons and ChumpCar series cage rules.


A Brief History of Iron and Steel


OK, this is a big tangent. It might not be boring to a racer - unless you are a metallurgical engineer. Modern race car roll cages are made from steel tubing (aluminum is not allowed) and picking the right alloy and type of tubing for the job involves both a rule book (General Competition Rules or GCR/CCR) and some engineering knowledge. There are generally TWO accepted types of tubing allowed for roll cages in SCCA and NASA: 4130 Alloy steel and 1018/1020 Low Carbon (aka: Mild steel) Steel DOM tubing.




Working as a Mechanical Engineer at a foundry in my first job out of college exposed me to a lot of practical metallurgical design and lots of different steel alloys. I also took a welding class at college, where we talked a lot about steel and iron and the changes welding can do to metal's molecular structures. That's where I learned that steel is the best metal on planet earth, and in many ways unique among all metals.


Iron is is, by mass, the most common element on Earth, forming much of Earth's outer and inner core (same scenario in almost any rocky planet). It is also the fourth most common element in the Earth's crust, which means it is relatively easy for humans to get at and mine. The production of iron by humans began sometime around 2000 BC and was so significant it began what is now called the Iron Age - when iron replaced bronze in implements and weapons. This shift occurred because iron, when alloyed with a bit of carbon, is harder, more durable, and holds a sharper edge than bronze. For nearly four thousand years, until replaced by steel after ~1870, iron formed the material basis of human civilization in Europe, Asia, and Africa. Iron has shaped human history for the past four thousand years, and it's use accelerated technological growth.




Natural "iron ore" has a lot of oxygen in it, so it is smelted at high temperatures to extract a more pure mass of iron. Carbon naturally gets mixed in at these high temperatures (along with 2-3 other elements) which means cast iron has a relatively high proportion of carbon (3-4.5%). This makes cast iron hard and brittle; it is liable to crack or shatter under a heavy blow, and it cannot be forged.


Blacksmiths learned to work iron - after heating it in a furnace at high temps they removed a pasty mass and hammered it on an anvil to drive out the cinders and slag and to compact the metallic particles. This Wrought iron (“wrought” means “worked” or hammered) contained generally from 0.02 to 0.08% percent of carbon (absorbed from the charcoal), just enough to make the metal both tough and malleable. Wrought iron was the most commonly produced metal through most of the Iron Age.


Steel alloys have a little bit of carbon in them (0.2 to 1.5%), enough to make them harder than wrought iron, but not so much as to make it as brittle as cast iron.


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Its hardness combined with its flexibility (from some other alloying elements) and high tensile strength make steel far more useful than either type of iron: it is more durable and holds a sharp edge better than the softer wrought iron, but it resists shock and tension better than the more brittle cast iron. After about 1856 (the invention of the Bessemer converter) and into the 1870's (Andrew Carnegie's grasp of the vital importance of chemistry in steel making) steel alloys became cheap to manufacture and exploded in use, replacing wrought iron rails in railroad tracks and other uses.


Some of the sources I used, other than past knowledge: This and this and that, and more.


Modern Roll Cage Steel Choices - 4130 vs 1020/1080 Alloys


There are two basic steel alloys used in roll cage structures and we will start with the "stronger" and more expensive alloy allowed: 4130. AISI 4130 alloy steel is about 97% Iron and has 6 other alloying agents that make up the last 3%. Chromium (0.80 – 1.10%) Molybdenum (0.15 – 0.25%) are the two key elements added that give this metal its higher tensile and yield strengths, and are the two most expensive elements in the alloy as well - hence the nickname "Chromoly Steel". These alloys are harder to weld properly (generally they are only TIG welded) when compared to Low Carbon/Mild steels. The yield strength of 4130 is 66,700 psi (67 KSI) and when this metal is used, a little LESS of this alloy is needed to achieve the same total assembly strength as Mild steel. It has a good strength to weight ratio, but the same density as all steels (all steel alloys and iron have nearly the exact same density, .284 lbs/cubic inch, due to the fact that all steel alloys are still almost entirely made of iron). In the past, roll cage rules allowed for thinner 4130 tubing to be used relative to Mild Steel, but that is no longer the case for most road racing bodies.


I used to use a lot of "A36" mild steel 15-20 years ago when I designed oilfield equipment, which had a minimum yield strength of 36KSI, which is relatively soft and very cheap. The modern 10XX series steels have gotten better and a lot stronger - closer in strength to 41XX Chromoly steels, but without the negatives. AISI 1018 and 1020 "Low Carbon" or "Mild" Steel alloys (also known simply as Carbon Steel) are lower cost and slightly weaker than 4130, but these 10XX series alloys have excellent weldability and offer a good balance of toughness, strength and ductility. Once cold worked (via the DOM or CDS process) these Mild steels become even stronger and stiffer.


1018 steel (0.14 - 0.20% Carbon) has a yield of 54KSI and 1020 steel (0.18-0.23% Carbon) has a 51 KSI yield - which isn't that far off of 4130 (67 KSI). Ultimately 4130 is about 20% stronger than Mild steel. But 1018 tubing that is DOM cold worked gets stronger, and is rated at 70KSI, and 1020 DOM tubing is rated is 65 KSI. Cold working 4130 tubing via the DOM process turns it up to 90 KSI yield... roughly 22% stronger.


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The key benefit to racers building roll cages out of Mild steel over Chromoly is that 10XX alloy steel is much more forgiving with respect to weld embrittlement and tends to "crash better" than the harder "alloy" steels. When you weld the 41XX series alloys the molecular structure of the alloy changes near the heat affected zone, especially if you put too much heat into the weld (and some welders like to "weld hot", which can really make the weld area change), so 4130 cages are almost exclusively welded with the trickier TIG welding process (a Tungsten tipped torch with a shielding gas and a separate metal rod, with a variable control on the welding arc).




Mild steel isn't nearly as susceptible to this issue and can be TIG or MIG welded and generally does not lose much strength at the welded joints. 10-20 years ago 4130 was all the rage for roll cages but lately 1018 or 1020 Mild steel is the norm, as long as they are DOM. To me nothing beats a properly designed, TIG welded, Mild Steel DOM tubing roll cage. This has the best combination of variables and the least number of compromises.


DOM vs ERW Tubing?




ERW or "Electro Resistance Welded" tubing is how steel tubing and pipe is made (at least initially) - where a continuous, flat roll hot rolled steel is bent around round (or square or rectangular) dies and welded at a seam (see image above). That's how lower cost pipe and tubing is left - with this visible welded seam on the outside and often a physical "ridge" on the inside of the tube (see below). This problem is - seam ultimately becomes the weakest point in this type of tubing. And the hot roll plate material isn't ever as strong as cold worked steel.



A visible seam and often a raised ridge is the result of the welding process from ERW tubing. All tubing starts as ERW...


The DOM process (Drawn Over Mandrel) takes ERW tubing and "cold works" it by drawing over a round mandrel and through round dies, inside and out. This makes the now DOM tubing "seamless" (its really hard to find the seam with your eyeball) and work hardens the steel structure - adding strength and removing the stress riser at the seam. ERW tubing was previously allowed in roll cages (up until just a few years ago) and the various CCR/GCR rules sometimes still reference ERW for "grandfathered" cages built before it was outlawed, but nowadays all roll cages are spec'd as seamless tubing - either 1018/1020 Mild Steel (DOM or CDS) or 4130 Alloy steel (DOM or CDS). There's another cold working seamless tubing process nowadays called CDS (Cold Drawn Seamless), but I can't seem to find any CDS tubing in common roll cage sizes - yet. The CDS specification seems to be more common in Europe. It could be the exact same process as DOM, but some U.S. tubing companies specify them separately, so I don't know.


The stiffness difference between ERW and DOM is shown in

, with the same diameter and wall thickness tubes of both types in a side-by-side bending test. The lower strength of ERW + the stress riser of the seam are why it isn't specified in roll cages any longer, but it was a pretty recent deletion from roll cage specifications.


The FIA has updated their specified tubing to 350 N/mm2 (50.76 KSI) tensile strength (see page 46, rule 8.3 of Appendix K here), and material is simply listed as "Cold drawn seamless carbon steel". They used to only spec 4130 alloy tubing (or the European equivalent) but even the French have seen the benefits of using Mild Steel DOM/CDS tubing. As we have seen with changes to rules specs, ERW is no longer allowed and the advantages in welding Mild Steel outweigh the weight savings or 20% strength benefits of 4130 Chromoly.


Picking the Tubing Material, Tubing Sizes and Cage Design Layout


OK, that got a bit long, but it was hopefully worthwhile tech. Now that we know why we use steel, know more about the alloys, understand the benefits of the cold working and seamless processes that are required in the steel tubing specified, and why more cages are using mild steel DOM - let's pick the cage tubing size for this build and show some Corvette cage pictures already!




Many of the cars we work on at Vorshlag lately, that are built around NASA specs, weigh over 3000 pounds so we're often using 1.75" diameter x .120" wall thickness DOM Mild steel tubing. And since the 1992-96 C4 Corvette is listed as a base class of TTC and a Minimum Competition Weight of 3203 pounds, I assumed that we had to use this tubing size. This is nearly the heaviest cage tubing in all of the NASA CCR, but lower weight cars can use thinner tubing diameters and wall thicknesses, as shown below (copied from the 2015 NASA CCR).


NASA 15.6.18 - Roll Cage Tubing Sizes


For the purposes of determining roll bar tubing sizes, vehicle weight is as raced, but without fuel and driver. Minimum tubing size for the roll

cage is:


Up to 1500 lbs:

  • 1.375” x 0.095” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical) or DOM
  • 1.500” x 0.080” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical) or DOM


1501 - 2500 lbs:

  • 1.500” x 0.095” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical) or DOM


2501 - 3000 lbs:

  • 1.500” x 0.120” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical) or DOM
  • 1.750” x 0.095” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical) or DOM


3001 - 4000 lbs:

  • 1.750” x .120” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical) or DOM


Over 4000 lbs:

  • 2.000” x 0.120” Seamless Alloy (4130), Seamless mild steel (CDS Mechanical) or DOM


Since we do not need to include the weight of the driver (200 pounds) or fuel (20 gal x 6 pounds/gallon = 120 pounds), that means our goal weight of 3203 really translates to a caged race car weight of about 2900 pounds. So we can use the lighter 1.75" x .095" wall DOM Mild Steel tubing. I like this for two reasons. First, we have a bunch of this tubing already in stock at the shop. And two, we typically bend 1.75" tubing, so our tubing bender has this set of dies already installed. Right now we're building two cages at once, both with 1.75" diameter tubing (one is .095 and the other is .120" wall), so we won't have to keep switching the dies. This thinner wall tubing is also easier to bend.


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We use a JD2 Model 32 manual tubing bender and dies


The weight is not insignificant: 1.75" x 120" wall DOM weighs 2.089 pounds/foot of tube length. The 1.75" x .095" wall DOM weighs 1.679 pounds/foot (19.6% lighter and about the same amount cheaper). The other choice for this weight is 1.5" x .120" wall DOM, which weighs more at 1.769 pounds/foot. Sure, we could have stepped up to a larger tubing size, but those CCR minimums are there for a good reason... mega-sized tube in a smaller/lighter car makes for less room to the driver and less energy absorption in a crash, so we're going with the recommended tubing range for a 2900 pound car, then picking the larger tubing diameter of the two options given there, which is slightly lighter.


Cage Layout and Design




There are three cage design options we can choose form the NASA CCR, shown in 15.6.8, -.9 and -.10. We're going with the "Forward Hoops" version from 15.6.8, shown above. This is the most common of the 3 methods (another is the "Halo style") and makes for the most room for the driver's head in a car like this. So about halfway through the day on Friday the 2nd, our fabricator Olof stared work on the cage install. He will build a majority of this cage while Ryan finishes a cage on another car at the same time.


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Before you can start bending any tubes you have to clear out the interior. This car was already gutted, which saved us 15-20 hours of labor. That work is never included in the "cage" price, which some people don't always understand. If you want to save some money, bring in a NAKED car with zero interior bits, like this. I came in early that Friday and removed the driver's seat and targa top, then the guys pulled the rear hatch glass off.


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The driver's seat normally weighs more than this, but it was alreay partially gutted by Matteucci and only tipped the scales at 34 pounds - I've weighed a lot of modern power front seats in the 60-75 pound range. The targa top weighed less than I had thought at 22 pounds. This is the plexiglass "See through" version, but I'm looking for a fiberglass version (both were offered from the factory) which we could paint white to match the car, but they sell for $$$ used. The weight is mostly in the metal frame structure, so the Plexiglass vs Fiberglass is probably a wash - except the fiberglass OEM version is likely stiffer. We might replace the Plexiglass with a custom Carbon Fiber skin (stiffer than Fiberglass). Is it legal? Well since we can run with the targa top removed (wouldn't that make its construction insignificant?) and as I read TT rule 8.3.B, we can lighten the "roof, hood, body panels and doors" as long as they "maintain their BTM (Base Trim Model) size and shape". The "no points" listing for I.h.20 says the same thing, with more details with respect to carbon/fiberglass doors being legal as long as the BTM body lines, hinges and handles are still operational. And an in-house built Carbon Fiber roof would be, you know, cool...


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The rear glass was much heavier at 46 pounds. That bit will likely never go back onto this car, as we have a formed, 3/16", trimmed Plexiglass rear hatch replacement inbound that should save 30+ pounds. I will show that in my next post, if it gets here before the NASA race Jan 17th. This is legal per the "No Points Modifications" rule I.b.8, as long as it has the factory BTM shape and no uncovered holes.


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Once the interior was cleared out enough to start Olof began cutting bits of fiberglass out of the way. See why I had the pictures of the C4 frame structures up above? That was to help us find where the frame is - which isn't obvious in some areas as there are big gaps between the shape of the interior fiberglass structure and the metal underneath.


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If you ever get a roll cage quote on a Corvette, now you know why it costs more than a traditional steel unibody car - because you have to cut access holes to get to the frame. And they need to be fairly big holes, to give the fabricator access to weld a reinforcement plate to the frame. Then you have to close up the holes in the fiberglass later... all of that is extra work.




Once you have access to the frame structure it has to be cleaned of all paint (we use a pneumatic wire brush tool called a "Crud Buster" along with a flap disc on an electric angle grinder). Then the plates are drawn in cardboard and transferred to steel, in this case 1/8" thick hot rolled plate (minimum thickness is .080" for these plates, but we tend to use .125", since it is stronger and easier to weld).


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Olof cut the plates and tack welded them to the frame at the main hoop, which is in an unusual spot. Normally the main hoop mounts to the floor behind the driver's seat - often 6-8+ inches behind the back of the seat. But in a Corvette, for tall-ish folks, the back of the seat ends up right at the rear bulkhead, so the main hoop has to go up on the rear deck area. The frame extends up here and we've checked with NASA inspectors on Corvette cage hoop placements and have also built cages in Corvettes like this. Miata cage main hoops are done the same way - just the nature of these 2 seat cars and their compact interiors.




On Monday the 5th, Olof designed and bent the main hoop, with help from our head fabricator Ryan. They got the hoop TIGHT up against the high strength steel roof structure, and placed it back the correct distance from my head. We had already done a number of seat mock-ups at this point and we knew where I needed to sit - with the seat almost touching the rear bulkhead. This put the main hoop where it is above.


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By this point we had switched our focus from the larger Kirkey aluminum seat we had in stock, to a PORNO RED! Cobra Suzuka Kevlar FIA seat we "horse traded" with a friend for. My buddy Jason McCall had ordered this seat from us last year for his 1989 Corvette but it wasn't fitting with the electric seat adjuster he wanted to use (for better fit with his shorter co-driver - his wife). It is brand new and still good through 2019 on the FIA certification.


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This seat happened at the 11th hour - the day Olof needed to start on the seat mounting and to lay out the harness bar. It turns out our aluminum seat fits better in his full interior C4 and his composite Cobra seat fits better in my gutted C4 with no slider. So we made a seat swaperoo!




Once more access holes were cut in the rear fiberglass (shown below left) the rear downbars could be cut, notched and built. These will land on 1/8" thick pads on top of the frame, as shown. Two thickness of pad, actually...


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One of the compromises made from our reduced timeline was that the cage became a weld-in 4-point roll bar, and then when we looked at the next step, it became a bolt-in roll bar. Now before you hurl insults, you have to realize that this is going to be a VERY beefy design that can still become a proper weld-in roll cage shortly after the first race. Weld-on "nut plates" (see above right) were created and access holes for the nuts were cut in the frame. This is because the frame is fully boxed and we couldn't bolt into the frame otherwise. These plates have nuts welded to the back side and will be seam welded to the frame, then a matching "footer" plate from the 4 main tubes will land onto these and bolt in place.


All this bolt-in nonsense was done for future access. After our first TT event we have a month off before the SCCA Club Trials event at TWS. During this break we can take the time to turn the 4-point roll bar into a fully welded in 6-point roll cage. The front cage section and door bars take the most time to fit, and we ran out of time. But to do the final welding on the door bars and A-pillar tubes, the cage has to be rotated forward and down, and this bolt-in rear layout will allow for this rear section to be moved for that access. Once the final welding is done up front the four "footers" of the roll bar portion will be welded to the frame plates, and the bolts can be removed. Make sense?


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Yes, that's a little crazy, but our 2 week timeline was just too tight to fully cage the car AND do all of the other performance, safety and maintenance work needed. Next up in the roll bar design is the main harness bar (which the shoulder harness straps will wrap around), then the main hoop diagonal. This is a horizontal bar that is kicked back from the main hoop about 5 inches, to allow for the shoulder harness adjusters to loop around the bar.


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The diagonal bar was cut and being tack welded in right before I made this post on Friday Jan 9th. One more tube is needed for the roll bar (a short tube connecting the harness bar and diagonal) and then it will come out for TIG welding. All of the pictures shown were just tack welds, which were done with the MIG. I'll show the rest of the roll bar and all of the other work happening next week in my follow-up "initial race prep" post. Gotta wrap it up!


Seat Mounting


Mounting a racing seat into a car is NEVER a fun job - installing a real racing seat is always a LOT more work than you might think. Ask any race car fabricator and they will tell you that this type of job sucks. We've installed a lot of racing seats over the years and it is never an easy "bolt-in". Any off-the-shelf seat bracket we've ever seen usually needs massive modification, and some of them raise the seat height by 2-5 inches. They only seem to work for little tiny short European children. Its a dirty little secret in motorsports - bolt-in seat brackets for fixed-back seats almost never fit.




And this only gets worse with drivers over 6 feet tall with racing helmets adding another 2-3" to their torso height. At 6'3", I'm not a good fit in many OEM seats much less with a racing helmet added. Here at Vorshlag there are 5 people that are 6'2" tall or taller, so we're all used to these seat mounting headaches. The Corvettes from C4-C7 are all pretty cramped inside as well, and we've had to really fight to make racing seats fit in these cars.


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In the most difficult situations (cramped cabin + tall driver) it is not uncommon to spend 6-8 hours fabricating mounts for one seat. Adding in a slider makes this take even longer, but we were out of room here and just mounted the seats directly to the floor (my co-driver Matteucci is almost the same height, luckily).


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Olof took most of a day to test fit the seat (with me sitting in it in a helmet), mock-up the angles and height, reinforce the floor, then modify the OMP side brackets (see image in this section) to get the seat bolted in where I had enough head room to the targa roof with a helmet on. It was tricky and he lowered the "lowest" mounting holes in the OMP brackets by about 5 inches. The original OMP seat mounting holes are crazy tall - doesn't matter what brand of brackets, this always happens.


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I don't have good pictures of the seat mounting from underneath, with the car in the air, but we have beefed up all of the seat mounting points to the chassis. The rear studs were removed and an 1/8" thick doubler runs across the entire width under the steel floor pan section. The front studs were also reinforced. We are adding clip-in harnesses so eyelets with reinforcement plates will go in for lap belt anchors as well as a solid mount for the anti-sub belt under the seat. Will show all of this next time.


Tires Are Everything


Its time to talk about the single most important aspect of this TTC build - the wheels and the TIRES.


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Tires are the most important aspect of a road race car. Let me repeat that for emphasis: Tires Are The Most Important Thing In Racing. The four tire contact patches are the only things connecting your car to the race track. Through these four little patches all of your forward accelerations, braking and cornering loads are generated. All of the work we do on the suspension is just to make sure the tires are happy - to make them stay flat, to always keep them in contact with the road, and to make sure loads are distributed as evenly to all 4 patches as possible.


So with this car being based in TTC class with a 7 point penalty, that leaves us with only 12 points to work with (19 class points - 7 penalty). And while that gives us some options for lots of different mods (upgrading power, brakes, suspension, lightening the weight, aero and tires), we're going to burn almost all of our points on the tires. This is a very critical decision, so let me explain what we're doing. This decision was made after hours of internal debate, hundreds of permutations of width + compound (+ other non-tire mods), but mostly comes from years of racing experience and knowledge: Knowing that the tires are almost all that matter.


TIRE WIDTH - As I pointed out in a previous post, everything you modify in the TT letter classes is either listed as a No Points Modification (which we are using every one we can!) or is assigned a number of points. It is all clearly stated in the TT rules. Tire width changes are "expensive", and the points in sizes increases above the "base class size" (TTC = 255mm) are shown below.


  • Equal to or greater than: 10mm +1, 20mm +4, 30mm +7, 40mm +10, 50mm +13, 60mm +16, 70mm +19, 80mm +22, 90mm +25, 100mm +28, 110mm +31, 120mm +34, etc.
  • Equal to or less than: -10mm -1, -20mm -4, -30mm -7, -40mm -10,


Big Wheels Keep On Turning!


As you can see you can get points BACK by going to a SMALLER tire as well. There is no other way in TT-Letter classes to gain points back, so this a big deal - and something we are going to do. Many will be surprised by this, as I've preached "BIGGER IS BETTER" for so many years. And while that is still true, we just don't have the points to go bigger, and feel that burning the points ALL on the compound makes more sense. Here's a comment from a corner-carvers reader and my reply:


Will the rules let you put 335's on? 17x12" rims are a bolt on affair.




Yes, it would is technically "legal" to run 335mm tires on a C4, but unfortunately the points just aren't there to do this and stay in TTC class. We're going to be running much narrower tires than that, but with what we feel is the right compound.




These pictures are of Jason McCall's 1989 Corvette that is prepped for SCCA BSP class (and was the National Championship winning car in 2005). It runs 17x11" CCW wheels in front and 17x12" wheels out back with Hoosier A6s in 315mm up front and 335mm out back. The fit is pretty tight - it has custom flared front "fenders" (the hood) and has the little 1996 Grand Sport "export" flares out back to make these fit - and we can legally add flares for zero points.




I've driven and ridden in this car and it is a GRIP MACHINE, just a big go-kart. Very fun, and the wide, sticky autocross compound tires he runs are why its so fast. And while I'd love to do this on our C4, the points for the compound (Hoosier A6 = +17 points and A7 = +22 points!) plus the increase in tire width (255->335 = +80mm = +22 points) would cost a whopping +44 points for just this tire upgrade. Using all of the points we have in TTC (19 - 7 = 12) and then even moving up to TTB (+20 more) we're still short by 12 points for a 335mm A7, so that tire choice would be a move straight to TT3. This is why we cannot use the tires we'd LIKE to use (I'd slap 335mm Hoosier A7 tires on this in an instant if the points allowed it!) but the compromise we have chosen will still work well enough - we suspect. Remember: Everything in racing is a compromise... and everything depends on everything else.


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Many of you that have experience with the C4 Corvette know that most of the later C4s came with a 275/40/17 tire on 17x9.5" wheels at all four corners, as did our 1992 Base Trim Model Corvette. But the TTC class "base tire" is 255mm, no matter what the OEMs put on the car. Wheel width is unrestricted, other than a track width change limit of +4 inches. Beyond that you take points. Our car has 285/40/17 old and crusty street tires on it right now, which would cost us (+30mm over 255) +7 points to use, but they are a joke. So hard they can spin freely through the first 3 gears. I won't be caught dead on a road course with old street tires, not even brand new 120-200 treadwear street tires (which are worth +2 points), unless the rules require that for everyone.


After racing our TT3 car in various "street tire" events/series last year, and at some tracks we also ran with R-compound Hoosier A6s in other series, I know the true lap time value of sticky R-compound tires. Going from a 335mm BFGoodrich Rival to a 345mm Hoosier A6 is worth a MASSIVE amount of time. On a typical 2 minute road course that difference is 5-7+ seconds per lap with the Hoosier over a 200 treadwear tire, and the Hoosier is MUCH easier to drive. So we're gonna stick with what we KNOW works and that has a great NASA TT contingency program: Hoosier.


TIRE COMPOUND - The compound of the tire is as important than width in Time Trial. Maybe even more important. Why? Because every TT lap is essentially run at a Qualifying lap pace, where you need to be pushing 10/10ths. To win you just need to set ONE fast lap per day (each day is a new competition), and waiting around for 3-4 laps for your "tires to warm up" will only get you mired up in traffic, as the front of the field catches the back end. There are a LOT of tire compounds listed and points assigned for each. The only "free" tire compound in TT-letter are those over 200 UTQG treadwear numbers. The tire models are grouped together with compound and performance parity, and the points given look to be pretty fair. There were massive adjustments made to these points for 2015, which was long overdue.

  • DOT-approved R-compound tires: BFG R1S, Goodyear Eagle RS AC (autocross), Hankook Z214 (C90 & C91 compound only), Hoosier A7, Hoosier Wet DOT (if used in dry conditions—see section 5.6) +22
  • DOT-approved R-compound tires: Hoosier A6 +17
  • DOT-approved R-compound tires and those with a UTQG treadwear rating of 40 or less not listed otherwise in these rules: BFG R1, Goodyear Eagle RS, Hankook Z214 (C71, C70, C51, C50), Hoosier R6 & R7 & SM7, Kumho V710 (note: Continental Tire Sportscar Challenge EC-Dry tires OK (225, 245, 275) +10
  • DOT-approved R-compound tires: Toyo Proxes RR, Hankook TD +7
  • DOT-approved R-compound tires and those with a UTQG treadwear rating of 50 to 130: Maxxis RC-1 (ex. Kumho V700, Michelin Pilot Sport Cup, Nitto NT01, Pirelli PZero Corsa, Toyo R888, Toyo RA-1, Yokahama A048, etc.) +6
  • (non-R-compound) tires with a UTQG treadwear rating of 120-200 (examples: BFG g-Force Rival, Bridgestone Potenza RE070, Dunlop Direzza Sport Z1 Star Spec, Hankook R-S3, Kumho Ecsta XS, Toyo R1R, Yokohama Advan A046 & Neova AD08,) +2
  • Non-DOT-approved racing slicks +30


That is a dizzying array of compound choices and, when combined with the size choices, it makes for a lot of possibilities. But we've run the numbers using these compounds + various widths and have settled upon: 245/40/17 Hoosier R7. Not the softest tire but damned close. Not the widest tire but "wide enough" (and it gives us a point back). The tire choices are still very limited in the brand new Hoosier A7/R7 compounds, but this seems to fit the bill. The spec's on this particular 245mm tire look pretty dang good, and I'm hearing good things about the R7 compound in tests. Our first event will teach us a lot... either we guessed right or made a big mistake!


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These wheels are stupid light! We will weigh the wheels alone once the old 275 Hoosiers that came on them are dismounted


WHEELS - We will run these Hoosiers initially on some 17x9.5" SSR wheels, which are both light and strong. Very light, in fact... around 15 pounds. Getting a set of these Corvette sized SSRs is like finding a wild unicorn - very rare and no longer made. SSR went out of business after the 2008 recession but it seems that they have reformed and are back - but not making a lot of the "big" sizes that fit Corvettes any longer. This set came from our shop manager Brad's former Super Stock 1994 Corvette, and he has two identical sets in perfect shape. I have dibs one set but the other is available. The Hoosier A6s on these wheels are DOT stamped from 2008! These wheels are perfect and have been sitting in his attic for almost 7 years.


What's Next


I could go on. And on. But I have probably bored you enough! Our crew is still busy at work finishing the prep on the Corvette for the first race and I'll try to do a quick update next week, right before we head down to MSR Houston Jan 16th. There's still a lot to do and not much time left...




Terry Fair - http://www.vorshlag.com

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But we've run the numbers using these compounds + various widths and have settled upon: 245/40/17 Hoosier R7.


When I first looked at this, I wondered how you were staying at 12:1. Then I noticed you said you were running a 30mm smaller than stock tire. Stock is a 275, so you are running a 245. This means you can take a power modification +0.8. Thus your raw p/w can be be 11.2:1 and still be legal.



Looks like I nailed your tire size too. I would have put money on a R7 in 245. It is the only thing that makes sense, because you need the points for suspension.


Tire widths are interesting. I agree that in general "BIGGER IS BETTER", but it depends on a lot of things. Overall, the difference in raw grip between a 245 and a 295 is next to nothing. This is physics. Tire compounds have some interesting characteristics that makes it slightly advantageous to be wider. But, the penalty for going wider is weight. It is unsprung rotating weight, so you take a huge performance penalty for tire weight. The real reason for going wide is to manage heat. All tires have an optimal operating temperature range. If you are overheating tires, going wider gives you more surface area reducing heat and letting it cooler more efficiently. Also the wider the tire the stiffer the sidewall. Sidewall flex actually generates a lot of tire heat. If you reduce flex you reduce heat.


Now as you said, in TT the goal is 1 flying lap. Thus, as long as you can do that early in a session, heat isn't an issue. This makes a narrower tire a good choice in TT. This is exactly why I'm only running a 205 on my MINI Cooper. I don't need a wider tire and a narrower tire weighs less and gives me points back.


Good work, Terry!



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Sterling Doc

Read the whole thing - interesting, and very well thought out.


I am debating tire size for my car as well. In ST3 I don't get points, but I do get HP, and my car will be pretty light - around 2600lbs as raced. I could run a 245 R7, which would give me around 24 HP over a 275 tire, which is about as large as I can comfortably go in the stock bodywork (maybe a 285, but it's not worth it to just break into the next HP adjustment range).



BJ, you should post up some details on your build as well!

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I am debating tire size for my car as well. In ST3 I don't get points, but I do get HP, and my car will be pretty light - around 2600lbs as raced. I could run a 245 R7, which would give me around 24 HP over a 275 tire, which is about as large as I can comfortably go in the stock bodywork (maybe a 285, but it's not worth it to just break into the next HP adjustment range).


Hey Eric!


You were the first to turn me on to the idea that tire width isn't everything when you were testing the 225/50R15 vs. the 205/50R15 for the 944 spec cars. I think 245 vs. 275 would come down to how the 245 would hold up over the course of an entire race. Testing different tires is expensive, but if you can run the same laps on the 245 vs. the 275, without more falloff on the 245, then the 245 would be fast because of the HP allowance.



BJ, you should post up some details on your build as well!


I will as soon as I have time to finish writing it. I've been so busy building the car that I haven't had much time for anything else. It will be down to the wire to get it ready for this coming weekend.


When are you going to come down here to Texas for a race? We have a growing ST field...



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Sterling Doc

Yeah interesting stuff. We could turn pretty similar lap time in a sprint race with a durable R-compound tire like the RA-1. But when we tries to do it with same size SM6 in a shorter enduro, we destroyed the tire to the point of it being non-drivable. Context means a lot. On the face of it, it seems like a 245 would be a lot of tire compared to the 225's I'm used to driving, and could keep under me for a whole 4 hour enduro, but then I wasn't putting much heat into the tires from acceleration, and braking.


I would love to get down, and see the shop some day.


Now, back on topic - metallurgy and 'Vette's - I'm learning a lot!

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Wow. There's certainly a lot of testosterone on display throughout this "blog" (and did I really just see a cross section image of the earth?).

Hope you can make it to a SE regional event this year.

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Project Update for January 16th, 2015: The first stage of "initial race prep" is completed and I'm going to try to write a QUICK update before we load up and I head down to Houston (in the next few minutes!) for the first NASA Texas event of 2015. We had a lot of parts delays but the crew at Vorshlag got everything on the "MUST HAVE" list completed. They only worked on this car over an 8 day period - due to other cars on the schedule. Big thanks go out to Olof, Ryan, Brad and Jon for all their hard work and long hours over the past week and a half. Thanks also to Jason and Tim for helping pick the mods and source the parts we used. Now all I have to do is drive the thing well... but I have a good back-up driver in Brian Matteucci, thankfully.


Brake Upgrade


The last week was a blur, as we had a lot going on in the shop with other customer cars, the phone rings off the hook in January (everyone waits until now to order parts for the new race season), and we're still gearing up for our new CNC machines - which has been a royal PITA. I had a birthday this week, and tons of other crap going on, and I usually work seven days a week playing catch-up on Vorshlag stuff on the weekends. But last weekend I stole a day away to swap on the front brakes.


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Left: The 12" front brakes are adequate but can be upgraded to 13" rotors "for free" (no points). Right: The two rotors in question


So the 1992-1995 "Base Trim Model" Corvettes all came with these wimpy looking front brakes, shown above. These include the 12.0" diameter x .810" thick vented rotor and PBR twin piston aluminum caliper, which I detailed a bit in my Dec 29th build thread post (post #5 for most of the forums). And I hinted that we would be able to upgrade from the 12" to the 13" rotor set-up for "no points". Normally this is a +2 upgrade, and we only have 3 total points left to play with. I'm saving those for later so we pulled the trigger on the correct rotors, calipers and caliper brackets back on Dec 23rd.


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The measured weights for the two front rotor sizes were pretty close to the spec sheets from Centric. Since nobody seems to want to work the last 2 weeks of a year in the USA, we didn't see these parts until late last week (around Jan 9th), and I started installing them on Saturday the 10th. The right front set-up went on fine, but I got bogged down cleaning the front suspension and wheel well...




It was worth it seeing the beautiful, forged aluminum uprights and control arms after 45 minutes of brake cleaner and WD-40 plus some elbow grease got 24 years of gunk and grease build-up off of the metal. Be careful with brake parts cleaner as it is pretty aggressive, but it cuts through the thick caked on grease well. Once I started to see metal underneath I switched to WD-40, and used WD-40 only on all of the plastics and rubber seals. Decades of road dirt wipes off after a little soak with WD.


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Cleaning the gunk showed me a split ball joint boot, which we will replace in another round up upgrades later (along with all of the original, crusty rubber suspension bushings - which can be replaced with any non-metal bushings). The old bits came off easily enough and the new 13" rotor and longer caliper bracket went on. And yes, we gained a solid 7 pounds in the rotor upgrade, but its "good" weight. This is cast iron that can both soak up brake heat and more rotor area and vanes to help radiate brake heat. This car will be 3203 pounds with driver and ballast and that's a lot of mass to slow down for thin little 12" brakes at both ends.


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The 2-piston sliding PBR calipers (3.56 pounds) are familiar to me, as I've used them on SN95 Mustang Cobras and 3rd gen 1LE/B4C Camaros in the past, as well as on my 94 Corvette - which had the Z07 package and these larger "J55" option 13" front brakes. The J55 calipers are wider, and the J55 caliper bracket (2.56 pounds) is longer, but neither is much heavier than the "base" brake parts.


How are we getting to use the "bigger" J55 brakes from the Z51/Z07/ZR1/GrandSport models without points? Well the trick is this: all 1996 Corvettes models came with the larger J55 brakes, including the base trim model. And the listing for the car we have (1992 Corvette) is listed as 1992-96 Corvette (non ZR1, non-LT4). So we're updating to the base trim level brakes for the 1996 model car, since the 1992-96 cars are listed on the same line (again, not the 1996 LT4 or Grand Sport). We can also play around with swaybars and springs from the 1996 base trim model cars, which we might do later. Here's the rule that makes it all happen...


Rule 8.5, page 41 of the TT ruleset for 2015:


Updating of parts between different model years of the same vehicle model is legal provided that the competing vehicle is both in the same model group listing (same line) in the Table in 8.2.2, and in the same generation of that vehicle model, and that the entire assembly is replaced. Backdating of parts between different model years of the same vehicle model is legal provided that the competing vehicle is both in the same generation and is in the same or higher base class. No interchange of parts between assemblies is permitted in order to create a new assembly.


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Just like in SCCA Solo, this "update/backdate" rule can be exploited to your advantage. It takes a lot of research and sometimes rummaging in junkyards, but it is there as a tool for dedicated racers to use. It helps to have factory manuals as well, which we do (thanks to Matteucci).


Again, this is a simple bolt-on upgrade and we have to use OEM (or OEM equivalent) parts to make it legal. No 2-piece rotors, no aftermarket calipers, this is all real deal GM bits. The brackets are from GM and the calipers are rebuilt GM calipers. So getting the right front corner swapped to the J55 bits took less than half an hour. I added blue loctite to the caliper bracket bolts, torqued it all to spec, re-used the old brake hoses (we will make stainless lines when we have time) with new crush washers, installed new caliper retaining pin and E-clip, easy.




Then a friend stopped by the shop mid-day Saturday and convinced me to go see the Interview at the Alamo Draft House. The movie was hilarious and I'm glad I went, but it put me behind on the right front brakes. No worries, I'll do it Sunday.... nope! Amy made me go write the eBay ad for our TT3 prepped 2011 Mustang, which I did then started writing the massive OUSCI 2014 write-up, which I finished today and promptly deleted (it was too harsh).


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So on Monday I came in and the guys were working on other items on the Corvette, so I got to work on the left front brake upgrade. As soon as I tried to put the left front caliper on, DOH! It didn't fit.




The box had the correct J55 caliper bracket (which moves the caliper out for the 1" larger diameter) but the wrong caliper casting. It was too narrow by almost .300" and would never fit over the thicker rotor (.300" thicker). Crap. We had ordered the right parts, and the part number on the box from Centric was correct, it just had the wrong damned part in it. Oh well, stuff happens. We took these pictures, sent them to Centric, let them kno how urgently we needed the right part, and hoped for the best.


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Left: original Delco/Bilstein dampers. Right: New Bilstein OEM replacements went on


Luckily they got the right caliper to us just in the nick of time (Wednesday the 14th!). The OEM replacement shocks also arrived at the same time (also ordered in December and also very very late) and Olof and Brad got all of that installed when I was out running errands that day. We replaced factory base trim model "Delco Bilstein" dampers with the OEM replacement Bilsteins that were listed in our Bilstein dealer catalog. The two original rears were blown and the new bits matched up perfectly. These are non-adjustable and are considered replacement OEM dampers available, so they are a "zero point" install.




We re-used the Carbotech brake pads Matteucci had purchased for the OEM brakes, which were XP12 front and XP8 rear. A little soft for my tastes but they were brand new so we will use them for this first event. We pushed some Motul RBF600 through the lines and it felt good. Too many other fires to put out to get to brake cooling this time around so we'll keep an eye on the fluid and Alcon temp strips at this first event.


Tires and Wheels Installed


The Hoosiers arrived this week Olof dismounted the 7 year old crusty 275/40/17 A6 Hoosiers that were on Brad's 17x9.5" SSR wheels. Then he mounted the 245/40/17 Hoosier R7 tires and balanced them. They did all that while I was at lunch one day and I didn't get to weigh the wheels without any tires, so I'll have to do that next time, but I can do simple math. Just weighed an old 275 Hoosier that was removed (22.40 pounds) and the weight of the wheels+old tires (38.76 pounds) that puts the 17x9.5" ET55 SSR wheels at about 16.4 pounds each. Not too shabby.




The SSR wheels were a bit dirty so I cleaned 7 year old brake dust off of the inside barrel and spokes with more WD-40 and some elbow grease. The 245 R7 looks so tiny to me, after a season of using 345 A6 Hoosiers, but it doesn't look bad on the car.


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We will see if burning 10 of our 13 class "mod points" on tire compound was worth it this weekend. This is an experiment that could pay off big or fail miserably.


Roll Bar, Harness, Seat and Fire Bottle Installed


With only 8 days of shop time we were not able to build a full roll cage (that will be a 3 week job by itself) but Olof did manage to get the roll bar built, reinforced, and mounted.




A big time suck on this job was making the aluminum cover plates. These are necessary on a fiberglass bodied car to cover the access holes in the body to the steel frame.


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Again, on a traditional steel bodied/unibody chassis car this step is not necessary at all. But its a Corvette, and has to be a pain int he ass. Olof used card stock to make templates (below) that cover the access holes, then transferred this into .065" thick 3003 aluminum sheet.




The sheet was cut, bent and welded at the joints to make a box-like shape that fit the funky fiberglass tub shape and covered the openings with about a 1/2" overlap. Then a few holes were cut to add small stainless steel button head bolts and riv-nuts were added to the fiberglass (these are special ones we use just for fiberglass, with a different grip length than normal sheet metal riv-nuts)


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A silicone bead was added to the perimeters of the fiberglass and these four, somewhat elaborate aluminum covers were then set in place and bolted down. These will now keep water, dirt and debris from spraying up from the tires and getting into the passenger cabin. Olof did a superb job and they look great and fit tight around the roll bare tubes. These can be removed and the roll bar unbolted for when we go back and finish the roll cage. Similar plates will be needed up front at the additional 2 lower points of the 6-point cage design.


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We knew we were going to be WAY too light for the class minimum (3203 pounds) and would need anywhere from 90-200 pounds of ballast. On Tuesday we were getting a little tight on time so I asked Ryan to step away from a cage job he was working on and make the ballast weight bracket from some heavy 1x2" tubing. I was thinking of something basic but he made this beefy assembly with a slick, threaded top cap that fits over a 2" tube.


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For ballast I purchased new 45 pound "olympic" style barbell plates with a 2" center hole. Typically cast steel weights like this cost around $1/pound, which is what I saw at a few places like WalMart. But after doing some shopping I found the best price at Academy sports, who had a wider assortment of better looking plates to choose from. These 45 pound plates were $31 each, or about $.68/pound. Sure, you can slum around on CraigsList and maybe find some mis-matched weights for around $.50/pound used, but its very hit or miss. Save yourself some hassles and go to Academy. If you want something more compact you can usually buy lead for $1/pound at plumbing supply stores, but just wear a mask when cutting or grinding on this stuff.




I didn't get any detail shots but the factory seat mounting studs (which are reinforced and rated for carrying up to 300 pound passengers) were used with some BIG bolts cut down on the lathe (and drilled/tapped to fit over the seat studs) go down from the top to secure the rack in place. You could pick the car up from this set-up and the 2" tube fits tight to the plates in sheer. At a minimum we will run 90 pounds of ballast here plus 120 pounds of fuel in the 20 gallon tank. Once we replace the 46 pound glass rear hatch with plexiglass we will add another 45 pound plate to the ballast box.


continued below

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continued from above


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The factory seat mounts are reinforced with extra steel from the factory, but we added more. 1/8" thick steel plate wraps around the stock stuff and was stitch welded to the floor as well as wrapped around up into the tunnel and frame on the sides, where it is bolted or welded for more support. The harness anchors for the lap and anti-sub belts are from G-force. These eyelets allow the clip-in ends from a Cobra/Schroth 6-point Profi-2 harness to attach. These are my favorite harnesses and made by Schorth in Germany to FIA specs. This set has 2" upper shoulder straps to better work with he NecksGen HANS device I will be wearing this weekend.




As usual, any "pretty" pictures you see here were shot by shop manager Brad with his Canon gear. The rest of the pics are from my "potato-cam" Galaxy S4 camera phone or my Nikon D90, which I can't seem to use worth a damn. The shoulder harnesses were wrapped around the harness bar tube with the proper wrap technique as specified in the diagram on page 42 of the NASA CCR.


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Last but not least, a 2.5 pound fire extinguisher was added. This is a small "Halotron" (Halon replacement) hand held fire bottle that can be used to put out small electrical, oil or grass fires and doesn't leave a big mess of dry chemical or foam residue behind. We add these things to every track build possible, even when they have a full fire "system" with multiple nozzles. No need to blow a big bottle when all you have is a little grass fire under the car after pulling off track into dry grass. We used the Drake quick release mount here, which we have used a half dozen times. CNC aluminum, roll bar or floor mounting with the same kit, and one pin can be pulled for fast bottle removal but it stays tight and rattle free when racing. Good stuff.


Weight Check!


Now you've seen how crazy I am about dropping weight and weighing everything in this and other build threads. Weight is the enemy! Lowering weight helps all acceleration vectors, be it braking, forward acceleration or lateral acceleration (cornering). We do a LOT to lower the weight on any race car build, and this car has gone from about 3300 pounds stock (we never weighed this car with the interior but that's what my 1994 Corvette weighed) down to about 2720 pounds. This weight drop was from lighter wheels, no interior, no passenger seat no side or rear glass, and no HVAC bits. The air conditioning compressor has been removed as have the headlights. The lighter wheels and tires help, too.


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Left: 2841 pounds with fuel but no driver or ballast. Right: 3200 with driver, fuel and ballast


We have added about 60 pounds in the roll bar and about 120 pounds of fuel (its nearly full) and the heavier J55 brakes and it was sitting at 2841 pounds. That's a solid 700 pounds lighter than our TT3 Mustang was without ballast or driver! Sadly we have to weigh 3203 pounds with driver (or else we have to burn points to run lighter), so ballast went back in in the above right picture to get us there. The plexiglass hatch should help remove about 30-35 pounds out of the 46 pound OEM glass, but it might not arrive in time, so we will save that 3rd 45 pound plate for then.


Classing Sheets, Dyno Test and Custom Tune


So we haven't built "letter" class car for NASA TT or PT before, but have helped a number of people class their cars. The base classing + mod points thing is nothing new to us. Just like TT# (numbered) classes, the TTx (letter) classes have an adjusted power to weight ratio. In TT3 the class has a 9:1 ratio but we were able to get ours to 8.8:1 with the adjustments. Likewise, TTC's base 12:0 pounds per horsepower limit has some adjustments as well, namely with a smaller tire...




Using the 245mm tire has had so many benefits and this is just one more - we get a 0.8 ratio bump for this small tire. That might not seem like a lot, but when you are at 3203 pounds it is nearly 20 extra horsepower allowed...

  • 3203 pounds / 12 = 266.9 whp (267 rounded up, in favor of the driver)
  • 3203/11.2 = 285.98 whp (286 rounded up, in favor of the driver)


Which is a good thing, as it was going to be hard to only make 267 whp even with a dead stock engine, manifolds, cats and muffler. We had the car over at True Street Motorsports yesterday and they were able to coax 284 whp and 331 wtq out of this 24 year old, bone stock iron block LT1, through the stock cats, manifolds and exhaust. Not too shabby. It even sounds better after the tune.



Above: Video of the stock LT1 motor at idle and revving, after the dyno test.


We have our dyno plot and classing sheet attached below. As you can see we've started with TTC + 7 penalty points, which left us with 12 points to play with. We got one back for running 245mm tires (-10mm below base class tire) for 13 points total. We burned 10 on the Hoosier R7 and still have 3 points to play with. We will be very stingy how we spend those this season, so stay tuned to see what we invest these points in to make Danger Zone faster.


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Left: The SAE corrected dyno plot making 284 whp. Right: TTC classing sheet with points


Last Minute Tweaks and Fluids


The Moroso oil pan for this motor is huge and the motor now holds 8.5 quarts of Mobil 1 synthetic oil (15W50 is my preferred weight for track cars), with a fresh Wix oil filter. Olof went over the car and filled out a NASA tech form but we still need to get a Logbook issued for the car at the event, so the plan is to leave Dallas early and make the 4.5 hour trek to south Houston on Firday and get there before dark. Then I can set-up the trailer, unhook, unload the C4, get the logbook tech and weighing, and make sure we have our ballast set correctly.


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I couldn't leave the massive openings in the hood where the pop-up headlights used to be so I asked Olof to make some aluminum brackets to bolt to the inner hood structure and to the existing holes in the headlight covers. Those went on and now forms a fairly seamless clamshell hood surface. The front turn signal and corner light assemblies were also reinstalled to fill holes. We will go back and make flush mounted aluminum covers later, when we have the time.


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Brad jumped into the Danger Zone this week as well and did a lot of wiring and some light fab work to the Corvette. He used to race a C4 himself and knows the car all too well. The wired AMB transponder from our TT3 car was moved to the C4 and Brad made some brackets for that, wired it up to a lighted switch (sometimes its handy to turn off the transponder - if we want to make another entry in the same car with the 2nd battery powered transponder we have). He also got the rear brake lights to work, after repairing some cut wires.




He made an aluminum panel to mount the switch in the center dash area as well as the 3-port "power panel" shown above. This was a cheap Amazon.com purchase which arrived in only a few days for $31 shipped. This panel has waterproof covers over a 12 Volt cigarette lighter port, a volt meter and a stack with dual 5 Volt USB ports (one a high amp and the other a low amp draw - see detail image above). Very slick little package that should prove handy when it powers my onboard vidcam and AiM SOLO timer. I will report back with how well this worked, or not.


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The formed, lightweight, plexiglass rear hatch we ordered a week and a half ago arrived this morning so there's no time to fit it, so we reinstalled the OEM back glass. Order Desk Manager Jon wrapped the "ugly" mis-matched door with white vinyl. He also designed, cut and mounted graphics for our logos, "DANGER ZONE", Hoosier and Bilstein decals, and some class/number decals for all sides of the car.


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Its time to load up so I didn't get the final pics... tune in next week for the post race update to see the final look, or look for it on Facebook with this hashtag #DANGERZONE.


What's Next?


The only thing on my RADAR right now, outside of cutting metal next week on our new CNC machines (tooling is FINALLY here!), is the race this weekend at MSR Houston. I will be paddocked with Costas, Matt White and other friends probably near Turns 16-17.


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We are running MSR-H in the Clockwise direction this time (they alternate the direction for NASA events every other year), so I haven't run this track layout since 2013. The video above shows the lap record I managed in the TT3 car 2 years ago, on the skinny 315 tires. The lap record for TTC is currently a 1:50 but I think we might be able to manage a 1:46 if everything manages to stay together on the car...





We have a pretty crazy class lined up: Our 92 Corvette, a 2003 Mini Cooper S (fully race prepped) and a 2005 Mazda RX8 (fully race prepped). Talk about an odd mix... and we will once again be the heaviest yet most powerful car in class, just like we were in TT3. I will post up more details after this weekends race. Until then...



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Nice to see someone breathing life into a C4. That said, it reinforces why pretty much everyone just gets a C5.

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Nice to see someone breathing life into a C4. That said, it reinforces why pretty much everyone just gets a C5.


The issue with C5s in Time Trial is that they go straight to the TT# classes, which can be a major expenditure just to tread water. The C4s are classed in TTD and TTC which allow some budget conscious builds to be competitive.

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