Keith Posted March 21, 2005 Share Posted March 21, 2005 Maybe I am reading this like a lawyer and I should stop... Regarding hp limits, the CMC rulbook states: GM 5.7 LT1: Horsepower: 250@ Factory RPM Range Torque: 300@ Factory RPM Range Late model GM cars may install a restrictor plate between the throttle body and intake manifold to reduce horsepower and torque to equal the 230 HP and 300 Torque of the early model GM cars. The diameter of the restrictor plate shall be noted on the Dyno Sheet and must match at all times. If you take the "lawyerly" interpretation of this, it is saying that you have two choices: 1) Unrestricted, you have to be 250/300 2) Restricted, you have to be 230/300 What this would implicitly mean then is that 250/300 restricted would not be permitted. Am I reading too much into this? Am I permitted to use a TB restrictor plate and be at 250/300? Thanks. Quote Link to comment Share on other sites More sharing options...
King Matt1548534716 Posted March 21, 2005 Share Posted March 21, 2005 Good question, but remember that either way, if you run 250/300 it has to be at the higher weight limit. Quote Link to comment Share on other sites More sharing options...
Keith Posted March 21, 2005 Author Share Posted March 21, 2005 Yeah, that much I understand and as long as the car is street legal (keeps the peace in my household) it will always be heavy. I have accept that driving my car is like driving a normal car with three of my fat friends in it... Quote Link to comment Share on other sites More sharing options...
King Matt1548534716 Posted March 21, 2005 Share Posted March 21, 2005 Well at least you can run to 257hp, since you're carrying the weight penalty one way or another, and that should be pretty easy to get to with or without a restrictor. I just weighed my Mustang last night, and the bad news is that I had completely underestimated the weight changes I'd made since the last time I scaled it. The good news is that I now only have to add about 50 pounds, which is a lot easier than the 150-plus pounds I thought I was going to have to add. Quote Link to comment Share on other sites More sharing options...
mitchntx1548534714 Posted March 21, 2005 Share Posted March 21, 2005 That's the way I'm reading it as well, Keith ... It says it here as well ... 8.7 Weight: Minimum weight for all cars listed below is measured with driver at all times: For early GM cars the min weight shall be 3150lbs For Ford cars the min weight shall be 3150lbs For late model GM cars: 1. With restrictor plate in place 230 hp / 300tq min weight shall be 3200lbs 2. Without restrictor plate at 250 hp / 300tq min weight shall be 3480lbs If one runs a restrictor plate, it HAS to be 230/300 @ 3200 or suffer a weight penalty if underweight. If you remove the restrictor plate, it HAS to be at 250/300 @3480 or suffer a weight penalty if underweight. No option of using a restrictor plate to attain 250/300. So, the only way you can get to the 250/300 number would be with exhaust restriction, like a Borla plate, muffler, small exhaust pipe ... 8.26. Exhaust All cars must use OEM stock exhaust manifolds. Any suitable exhaust system may be used after the OEM stock exhaust manifolds. The exhaust must exit behind the driver and be directed away from the car. Mufflers may be required to meet sound regulations depending on track location. Quote Link to comment Share on other sites More sharing options...
bsim Posted March 21, 2005 Share Posted March 21, 2005 It's alot more simple than that. There are 2 hp limits based upon weight. You either weigh more and make more power, or weigh less, and make the lower power. Trying to read that restrictors are not allowed at the 250 limit is incorrect. Restrictor or not, the limit is the same. SO: Am I permitted to use a TB restrictor plate and be at 250/300?YES. In fact you're required to if you are over the limit. Quote Link to comment Share on other sites More sharing options...
mitchntx1548534714 Posted March 21, 2005 Share Posted March 21, 2005 Brad, that was the way I have been interpretting the rule all along. However, when the rule says ... WITH restrictor plate 230/300 @3200lbs. minimum WITHOUT restrictor plate 250/300 @3480lbs. minimum It doesn't allow any wiggle room to run a restrictor plate AND run at the higher power/weight. If you install a restrictor plate, it HAS to be at 230/300 ... Remember, if it doesn't specifically say you can, you can't. Quote Link to comment Share on other sites More sharing options...
Keith Posted March 21, 2005 Author Share Posted March 21, 2005 So I'm not being a dope! Reading it literally like a lawyer, you can either be 230/300 restricted or 250/300 unrestricted. Reading it as a sensible person, it's 250/300 restricted or unrestricted... Since I have both answers to the final question in my original post - I guess I need Tony or Al to chime in. Quote Link to comment Share on other sites More sharing options...
mitchntx1548534714 Posted March 21, 2005 Share Posted March 21, 2005 I don't think so ... and to be perfectly honest, I think Brad's interpretation is correct .... at least the intent of the rule is as Brad interpretted it. Finding these kinds of caveats is the evil that is governing rules ... Quote Link to comment Share on other sites More sharing options...
Keith Posted March 23, 2005 Author Share Posted March 23, 2005 I spoke with Don Trask today and here's what he said: Restricted, you must be 230/300 at or over the specified weight or take a 10lb weight penalty for each hp AND each ft-lb over either of the limits. Unrestricted, you must be 250/300 at or over the specified weight or again take a 10lb weight penalty for each hp AND ft-lb over either of the limits. Essentially, the example table that is in the CMC rulebook for the 250/300 descrition also describes the 230/300 situation for LT1's. I think this is the source of my confusion - the "general" table applies to Mustangs, 3rd gen f-bodys and restricted LT1's. The "LT1" table only applies to unrestricted LT1's. For example (and this is the one that we discussed): If I was restricted and at 235hp/302ft-lb, I would require a 50lb penalty for the overage on hp and a 20lb penalty for the overage on torque. Therefore, as an LT1 driver in this example, you'd take the minimum weight for the restricted 230/300 of 3200lbs and add the 50lbs and 20lbs above yielding a new minimum weight for this car as 3270. I guess the rulebook is encouraging LT1 guys to run restrictors, huh? Feel free to chime in... Quote Link to comment Share on other sites More sharing options...
King Matt1548534716 Posted March 24, 2005 Share Posted March 24, 2005 Did you ask him for an answer to your original question about using a restrictor to get down to the 250/300 level? If using a restrictor plate is not allowed at that HP level, what other methods can be used to reduce the power? It seems to me that as long as you are at the legal weight for the power you are making, it shouldn't make a difference if you have to choke the exhaust, retard the timing, tape off the air filter, swap pulleys, or run a restrictor plate to get there. Quote Link to comment Share on other sites More sharing options...
Keith Posted March 24, 2005 Author Share Posted March 24, 2005 No I didn't ask. To me, my most important mod is seat time and I am just looking to not to anything illegal. I'm not sure I understand the underlying reasoning behind some things, but I am willing to follow the rules and see what I learn. Quote Link to comment Share on other sites More sharing options...
Members Al F. Posted March 24, 2005 Members Share Posted March 24, 2005 There is little doubt in my mind that we are going to have to revisit the entire horsepower and torque deal, if nothing else to make it easier to understand and apply. And just for the record, I really don't like this sort of discussion, but it is a necessary evil in this disease...er hobby You'll notice there is no mention in the rules anywhere allowing Fords or 305s to run restrictors. This is because the original rule makers did not think you'd need them. They figured it was easy enough (or hard enough, depending on your perspective) to get to around 230/300 with a bone stock engine. They even went as far as putting up a fairly forgiving tolerance, simply letting the driver compensate by adding weight. Enter the LT1...something must be done to get this thing competitive since running the heavy option is considered to be less than ideal. But how do you literally detune a car? Well, do what the Nascar boys do and slap a restrictor plate on it! Bitchin'!!!! It works like a charm. Last year when we had all the endless discussions about rules updates, we never discussed adding the option of using restrictors for other configurations. Simply put, it had never come up. Mustang guys never need it, neither do 305 drivers...and nobody was interested in running heavy 4th gens. Seriously! SO, if it were up to me and only me (which it isnt) I would interpret the rules as written today to not allow a 250hp LT1 to have a restrictor, same as 5.0 Mustangs dont have restrictors. If Tony/Mike/Greg/Don disagree then we'll have to get together and hash it out. Is that the most practical situation? Well, maybe, maybe not. Its really easy to tune an engine to an exact hp/tq max with restrictors. It gets a little more complicated if you're using mufflers, filters, etc...but consider that the "intent" (there's that word again eh?) is to run STOCK drivetrains. If you're over the hp limit, and you got there using an aftermarket Y pipe, and under drive pulleys (Keith's very same situation) couldnt you make an argument that it would have been cheaper to not add that stuff in to begin with? (Keith probably had that stuff already, whatever, I’m not picking on you Keith just using you as an example) Does a bone stock LT1 make more than 257/307 at the wheels? Because our understanding is that they don’t. Keith's situation lends some credibility to that. Consider as well that this is accepted as not being an option for Fords and 305s. If we allow heavy LT1s to use restrictors to optimize their power, should we not also allow Fords and 305s the same luxury? Don’t misunderstand me, its not that I am not sympathetic or want to make other’s lives difficult, but there are two approaches you could take to getting your motor set up: 1)start with a bone stock motor, then add allowed modifications to work your way up to approach the limit, as opposed to 2) add in every allowable modification and then restrict down to approach the limit. I am of the opinion that you should always use approach #1 unless you’re running the 230/300 LT1 option, which is therefore the only one that should need restrictors. Quote Link to comment Share on other sites More sharing options...
Keith Posted March 24, 2005 Author Share Posted March 24, 2005 One last dumb question - I assume that restricted, the 257/307 example in the table in the rulebook is the hard upper limit? I am starting to worry that the smallest restrictor plate (33mm) that I have still may be too big. Regardless of where this plate puts me, this will be my last dyno pull until Mid Ohio next weekend. I am out of time. ...and to anyone reading this I need to clarify the motivation behind my posts: I am not trying to sneak in just-under the limits. Really. The reality is that I had an uncompetitive AI car last year and I am trying to minimize the required mods, timeframe and associated costs with making it CMC-legal. I just want a simple car that is within the rules to I can forget about it and learn to drive better. Maybe someday I'll crack the rulebook with a mind towards gaining a hp or losing a couple of pounds but my driving isn't nearly good enough to worry about these things yet. If you don't believe me or what I am saying, come sit in my passenger seat and listen to the stereo with me sometime. You don't have these things (or an emissions-legal setup) if you are really focused on cutting things close. Quote Link to comment Share on other sites More sharing options...
Members Al F. Posted March 24, 2005 Members Share Posted March 24, 2005 Keith I hear ya, and that's the right way to look at it. There's nothing wrong with trying to get the car to be fast, and there's nothing wrong with not worrying about the car and just worry about the driver Since you didn't comment on my post, I'm assuming you meant 237 for restricted hard limit, which is correct. Quote Link to comment Share on other sites More sharing options...
Keith Posted March 24, 2005 Author Share Posted March 24, 2005 Yeah, I was asking about the restricted limit. I guess I need to get to that or preferably lower. Quote Link to comment Share on other sites More sharing options...
Glenn Posted March 25, 2005 Share Posted March 25, 2005 i do think an stock LT1 will make more than 250/300. all i did to my car was dump the cats and install a bullet muffler and made 285/325. did my $50 exhaust make 35hp/25tq? i think not. if it did, i need to jig it up and sell it. i also dont see how anyone would think a car @ the 250/300 power level @ 3480 (?) lbs has any kind of advantage due to the restrictor alone. so if my car made 260/310 hp/tq i would have to add weight on top of the 3480 minimum to be legal? dont think i agree w/ that. i do agree that 2 years ago this was not seen as a possible problem. i see no problem w/ adding a restrictor to get to either power level you choose to run. some people are keeping there CMC cars 100% street legal and should not be penalized cause they arent willing to strip and gut the car to get to the 3200 lbs and 230/300 limit. please give me any technical info regarding the advantage a restrictor adds. Quote Link to comment Share on other sites More sharing options...
mitchntx1548534714 Posted March 25, 2005 Share Posted March 25, 2005 Al, I understand the points you made. And I think Glenn makes a very valid point as well. Let's use Keith as an example. He has a street legal car, that makes 7hp more than allowed. So, he is faced with either ... ... restricting the motor to 230hp and then gutting the car, detroying any public value, maybe in the 1000s of dollars ... or ... restricting the motor to 250hp and leaving everything alone, retaining the normal value of the car or ... take a 70lb weight penalty and go racing. The arguement made over and over is about "follow the leader". The near 300lb weight difference of running 250hp is a significant penalty in of itself. So, I really doubt anyone will buy a Y-pipe and U/D pulley in order to gain 20hp and then add 300lbs of ballast. There is intent and then there is reality ... Based upon what Glenn's car came in at, I figure mine, with my lard ass in the seat, will come in between 3350 and 3400. A new 96/97 LT1 put down 265-275 at the wheels, through cats and a smooth bellows. I really see no downside to restricting an LT1 motor to 250/300 and running at 3480. Quote Link to comment Share on other sites More sharing options...
Keith Posted March 25, 2005 Author Share Posted March 25, 2005 Both of your points about stock LT1's are fair. I've seen my dad's very lightly modded LT1 dyno at 25x/3xx... ...and that was on a Mustang Dyno. I guess I'm willing to sit back and see how things play out. I just hope to God that the smallest restrictor plate gets me around 230hp. Otherwise, I'm hosed for Mid Ohio. Quote Link to comment Share on other sites More sharing options...
Glenn Posted March 25, 2005 Share Posted March 25, 2005 it took the smallest one (31mm) for me to get below the 230/300 mark. the 33mm was close, but we just couldnt get it below the limit. i hade al make me a custom 32mm. it will go on before next event. Quote Link to comment Share on other sites More sharing options...
Members Al F. Posted March 25, 2005 Members Share Posted March 25, 2005 Yeah, it may be possible that 250/300 just isn't the right target for an unrestricted LT1. The Mustangs were rated at 225, and the limit for CMC was set to 230. This makes sense right? You gain power due to dumping exhaust etc, but lose power due to measuring at the wheels...probably a break even deal. But the LT1s were rated at 285...which means its very likely we have cars making more than 257 right out of the box. Guys, fundamentally I dont disagree with you about restrictors not in and of themselves being a bad thing. All I'm pointing out is the way we set up these rules, you're not allowed to use one unless your peak hp ave is 237 or less. BUT...no one wanted to run heavy LT1s until now, so maybe this was broken all along and no one realized it because no one cared. Quote Link to comment Share on other sites More sharing options...
Keith Posted March 26, 2005 Author Share Posted March 26, 2005 I installed Jason's/Christine's 33mm plate on my car this morning (nice job Al!). I have my fingers crossed for tomorrow. Quote Link to comment Share on other sites More sharing options...
mitchntx1548534714 Posted March 26, 2005 Share Posted March 26, 2005 Guys, fundamentally I dont disagree with you about restrictors not in and of themselves being a bad thing. All I'm pointing out is the way we set up these rules, you're not allowed to use one unless your peak hp ave is 237 or less. BUT...no one wanted to run heavy LT1s until now, so maybe this was broken all along and no one realized it because no one cared. I think you may be right. These cars are heavy cars. I am removing every bracket, wire, bolt and nut I can to help me weight wise. I've even given up peanut M&Ms ... Is it possible to get a waiver to run 250/300 with a restrictor plate till the rules can better address this issue? Paying 280lbs for 20hp is a heckuva penalty in of itself ... Quote Link to comment Share on other sites More sharing options...
tacovini Posted March 26, 2005 Share Posted March 26, 2005 Mitch...why don't run your first race before we start talking concessions on the rules! Who knows where you'll shake out and in your rookie season it'll be more about seat time and less about those 20 horses or 200 lbs. Hope that didn't sound harsh but we need to get a sample of 4-5 weekends of runnin' flat out and hard until consideration of rules changes starts kickin' in. Isn't Don's black/silver car up in the left corner of the forum (with me doggin' him) an LT1 car? That car was heavy but very competitive, no? Someone will remind me, I'm sure. -=- Todd Quote Link to comment Share on other sites More sharing options...
mitchntx1548534714 Posted March 26, 2005 Share Posted March 26, 2005 I understand, Todd. And you are correct. I live 100 miles from the dyno of choice and I was just trying to find a target, get it there and be done. Quote Link to comment Share on other sites More sharing options...
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