Re-engine of CMC '88 Mustang: valvetrain questions

[jesm]

Hi- just bought old #46 and first time I drove it oil pressure dropped to about 5 psi. Maybe the oil pump/shaft issue, but I am gearing up to do a re-engine. Bought a used .030" over 302 with about 10k miles on it that was professionally built. The rules said '97 Explorer induction is OK, so I got a rebuilt set of GT40P heads and an Explorer intake with all the parts. Got an E303 cam to time it and converting to mass-air. Finally questions: 1.6 or 1.7 rockers are ok if they are steel? Do I need to worry about making too much power and put the cam in advanced some? Thanks in advance- point me to an old post if you have one. Did a lot of searching but didn't find it. First use of car is to get me through HPDE, but I don't want to rebuild it out of spec.

[soundguydave1548534741]

IIRC, the 1.7 rockers are Cobra stock valvetrain parts from 94-95 (when they had the 302W), and as long as you're using the OE parts, they are legal per 7.11.1, as they are "in OEM stock configuration." FWIW, they are still available!

[jesm]

IIRC, the 1.7 rockers are Cobra stock valvetrain parts from 94-95 (when they had the 302W), and as long as you're using the OE parts, they are legal per 7.11.1, as they are "in OEM stock configuration." FWIW, they are still available!

Thanks for the reply soundguydave. Do you have a source for them? I have been reading they are discontinued and used ones are probably all cracked. Big question is: Do I need to move the powerband down with this setup? I have heard 1.6 vs 1.7 lowers the powerband by 300 rpm.

[RichV]

Yes, the 1.7s are good. They are actualy Crane aluminum 1.7s and they have ford part #s stamped on them.

 

As far as power, make sure the GT40P heads have valvetrain that can handle higher RPM. OEM Explorer stuff will not work. I've seen people make anywhere on the nose at 260 to 299. It depends on other things, CR, ECU, tune (fuel PSI and timing), exhaust, etc. But you have the bases covered. Put it together and see where it lands. You have HPDE time to sort it out.

[jesm]

Thanks for the tips- I just got my performance drop in springs from Alex's Motorsports today. http://www.alexsparts.com/sb-ford-gt40p-drop-in-valve-spring-kit-hyd-roller/ Got the hardened shims, viton seals, and height gauge too. I have no idea about the tuning options you mention. Got a primer link on that for me? I was going to toss it to the computer to sort out. Heard the Explorer injectors are good too, so I'll see if the used ones I got are any good. Thanks again.

[jesm]

The rest of the story-- It's a 10:1 motor, with an 89 stock computer and shorty headers. I do know about regulating fuel pressure and changing timing- thought you meant an ECU tune, which I thought was not allowed. How about putting the E303 in 2 or 4 degrees advanced to further lower the peak power? Anybody doing that, or is that too much of a truck motor then?

[37Stang]

Thanks for the tips- I just got my performance drop in springs from Alex's Motorsports today. http://www.alexsparts.com/sb-ford-gt40p-drop-in-valve-spring-kit-hyd-roller/ Got the hardened shims, viton seals, and height gauge too. I have no idea about the tuning options you mention. Got a primer link on that for me? I was going to toss it to the computer to sort out. Heard the Explorer injectors are good too, so I'll see if the used ones I got are any good. Thanks again.

 

You may already know this but the best way to set up a durable valvetrain is as follows:

 

When you get your springs take each one and put them in a vice and crank them down until they coil bind. Take a set of dial calipers and measure the distance between the vice jaws. This is your actual spring coil bind. If they are dual springs keep an eye on the inner spring as you move closer to coil bind as the inner spring or damper will sometimes coil bind before the outer spring. Each spring will have a different actual coil bind measurement. Of course, write down the coil bind figure for each individual spring.

 

Get an old set of Ford roller lifters and tack weld the plunger to the body of the lifter or shim them up solid. This is so there is no plunger movement while you are setting up the valvetrain geometry. Mock up the block with the crank, timing chain, cam and heads with whatever valve springs you have laying around that will handle the lift. Set up the valvetrain geometry and put a dial indicator on the retainer of your valve springs. Measure the actual lift of each and every valve. You want to do this individually because those cast aluminum rockers will not be a true 1.7.

 

Now that you have proper geometry and your actual lift numbers you can do a little math and come up with your installed heights...

 

Coil bind figure + .060 + valve lift = installed height

 

Some folks say .100 from coil bind is good enough but the closer you can run the springs to coil bind the better to dampen harmonics and reduce spring surge. I have personally run PAC springs as close as .040 to coil bind but have been "creeping" up on running them that close for a few years.

 

Don't worry about the spring pressure being too much. I have seen folks run 375lbs on the seat and 700lbs over the nose on factory Ford roller lifters in drag race applications turning 9200 rpm. You will suffer more valvetrain problems with a roller cam, hydraulic or solid, with too little spring pressure over too much spring pressure.

[37Stang]

The rest of the story-- It's a 10:1 motor, with an 89 stock computer and shorty headers. I do know about regulating fuel pressure and changing timing- thought you meant an ECU tune, which I thought was not allowed. How about putting the E303 in 2 or 4 degrees advanced to further lower the peak power? Anybody doing that, or is that too much of a truck motor then?

 

Although I don't have any experience with the E-cam I have never personally witnessed one single time were advancing a cam hurt performance. The most important valve event is the closing of the intake valve and the sooner you can close the intake valve the better.

[RichV]

Cam advance and ECU tuning are both not legal in CMC. Fuel pressure and timing are adjustable but must match your dyno sheet.

[jesm]

Thanks RichV. Solves my problem of how to set up the cam. Thanks also on the valvetrain setup. It will be my first one, but my 550 hp 408 Windsor for my '70 Mustang street rod is right behind it. I need a bumper sticker: "My daily driver is faster than my race car"

[CMC#11]

My guess is the setup you are talking about will make way more than 2 60 hp. Corey Rueth in TX is the only person I am familiar with that built a 5.0 w/ the GT40P heads. IIRC, he made around 295 hp and then had to restrict it down to 260. Your aftermarket shorty headers will also kick up the numbers quite a bit.

 

I run the GT40 heads w/ stock manifolds and am at 261hp with only running 11 degrees timing. Making power is pretty easy w/ the stock Cobra parts.

[jesm]

HP at the wheels? I thought it might come out too high. Maybe I should only run the HO intake and manifolds with the GT40P heads.

[MHISSTC]

For comparison sake, our engine makes right at the target numbers with no restrictor plate using the following configuration:

 

'94 Cobra base engine with stock GT40 heads, cam, and stock roller rockers rebuilt with a small overbore

'93 Cobra intake and throttle body

Ford Racing ceramic coated unequal length shorties into side exit dual exhaust with x-pipe

Summit Racing underdrive pulleys

19# injectors with '88 Speed Density computer

43# WOT fuel pressure

14 deg. timing

[CMC#11]

HP at the wheels? I thought it might come out too high. Maybe I should only run the HO intake and manifolds with the GT40P heads.

Yes, at the wheels.

I'd definitely start with the stock manifolds. Almost every 5.0l can reach the 260hp limit but I don't know of a single one that can get near the 310tq limit. All here in TX are b/w 285-295tq.

[jesm]

Maybe I should return my E303 cam and go with a GT40 cam. Is there a spec for that cam? That way I wouldn't have to do the Mass Air conversion now. It is an '88 Speed Density car.

[jesm]

Anyone have a strategy for a 310 ft lb 302 that's legal?

[MHISSTC]

True for us too on making the HP numbers while being a few shy on the TQ.

 

The story goes that the Cobra intake improved the top end breathing and sacrifices a bit of TQ for HP. Supposedly that's why Ford went back to the T-bird cam to improve TQ numbers for the Cobra.

 

No spec cam, just stock OEM Cobra cam. If you give me a little time, I can probably come up with a Ford part number for you along with more complete referenced information to what I've already stated.

[jesm]

Thanks Scott. So I can use the stock Speed Density setup too? That would be a way easier build to use the stock HO intake and computer with the GT40P heads- maybe even the HO manifolds. It's kind of counter intuitive to stop thinking HP and think TQ! I also have a set of the stock heads with a recent 5 angle valve job. Any thoughts on the option of using them instead of the GT40P. Giving up the extra compression is probably too conservative though.

[MHISSTC]

Mmmm... I can't give you very good guidance on that because I haven't built the motor you describe. I will tell you the standard formula is to build a stock Cobra engine with legal add-ons like underdrive pulleys and shorty headers in order to make the numbers you are after.

 

I'd really like to see someone who has an engine like ours swap the Cobra intake with the H.O. intake to compare TQ and HP numbers. But from what I understand, the intake becomes the choke point and the engine really starts falling off quickly at higher RPMs. We also can't do anything to substantially increase the redline. Does't the computer start cutting the fuel or spark at 5250-5500 RM? Ugh... I used to have all of this information on the top of my head, but it's been several years since I've researched it.

 

Yes, the stock speed density system will work fine to make the target numbers. The 19# injectors are near the upper end of their duty cycle, but bumping up the fuel pressure will help some.

 

Is your engine still together or already torn apart? If it is still together, try maybe you could dyno it as-is and see where you are now.

[37Stang]

Cam advance and ECU tuning are both not legal in CMC. Fuel pressure and timing are adjustable but must match your dyno sheet.

 

I just skimmed the rules but can you point out to me the rule that states the cam can not be advanced?

[jesm]

Both the broken engine and the new engine are still together, but for the cost of an engine dyno run in my area ($500 min.), I could pay for the whole new setup. Who knows what the rules will be in two years when I finish HPDE anyway, so I'll just build a solid motor that complies with the rules. Was hoping someone had figured out how to get the HP and torque to the limit, but maybe that will be me Thanks for all the suggestions. I too would like to see where the rules disallow the cam advance or retard. I didn't see that spelled out. Cam advance should shift the power curve to peak at lower RPM and it sounds like my setup will have too much peak power, so getting power earlier with a legal peak power sounds attractive.

[Glenn]

Cam advance and ECU tuning are both not legal in CMC. Fuel pressure and timing are adjustable but must match your dyno sheet.

 

I just skimmed the rules but can you point out to me the rule that states the cam can not be advanced?

 

Cause it didn't come that way from the OEM. It has to go in straight up dot to dot.

[MHISSTC]

Both the broken engine and the new engine are still together, but for the cost of an engine dyno run in my area ($500 min.), I could pay for the whole new setup. Who knows what the rules will be in two years when I finish HPDE anyway, so I'll just build a solid motor that complies with the rules.

 

The folks in CMC have done a pretty good job already in figuring out how to get the 5.0 engines to make the power consistently and reliably. Not that you couldn't figure something better out, but it's going to be a lot of effort for minimal return. I would consider the information here to be much better than most of the Internet because folks here have actually done it, and have the numbers to prove it without the nearly endless speculation found elsewhere.

 

Point of clarification: the dyno run I was talking about was a chassis dyno run to get the HP/TQ numbers at the rear wheels and not an engine dyno run. $500 is too much to spend on such a thing. I know in the Rocky Mountain Region we get together at least one day each year before the season starts to all do our chassis dyno runs together. Similar conditions on the same dyno on the same day makes for consistency between racers.

 

If you're planning on HPDE for a while before getting your comp license and making the jump to CMC, I suggest you put whatever is running in the car and drive it like that for as long as you need to. During that time you can continue your research and talk to different folks, save up, and build your engine once, just the way you want.

[37Stang]

Cam advance and ECU tuning are both not legal in CMC. Fuel pressure and timing are adjustable but must match your dyno sheet.

 

I just skimmed the rules but can you point out to me the rule that states the cam can not be advanced?

 

Cause it didn't come that way from the OEM. It has to go in straight up dot to dot.

 

The E-cam didn't come installed in any OEM Ford vehicle. The manufacturing tolerances of the FRPP cams are all over the place. I looked over the rules again and did not find any thing that stated it has to be installed "dot to dot". Is there a specific rule I am missing that states it has to be installed "dot to dot"?

[Glenn]

Cam advance and ECU tuning are both not legal in CMC. Fuel pressure and timing are adjustable but must match your dyno sheet.

 

I just skimmed the rules but can you point out to me the rule that states the cam can not be advanced?

 

Cause it didn't come that way from the OEM. It has to go in straight up dot to dot.

 

The E-cam didn't come installed in any OEM Ford vehicle. The manufacturing tolerances of the FRPP cams are all over the place. I looked over the rules again and did not find any thing that stated it has to be installed "dot to dot". Is there a specific rule I am missing that states it has to be installed "dot to dot"?

 

Try reading the 1st rule in the CMC rules.

 

1. INTRODUCTION

The following rules are not guidelines for this series but an actual listing of allowed and required modifications. The only legal modifications are those specifically allowed by applicable rules. If not specifically allowed, any modifications are prohibited. Some equipment may be required to support the sponsors who have contributed to the year end points fund.