Guess my horsepower

[hungerbuhler1]

I've tried two different modules and coil packs. I've tried gapping the plugs at .025 and it ran like crap. I set the gaps back to .030. Today I bought some fittings so that I can hook a pressure gauge up to the header, before the turbo, to measure the back pressure. I just want to rule-out a back pressure problem. The next test I might do is set the lifters to zero lash, just to rule out defective lifters that may be prematurely pumping up. This engine does not RPM past 5850. Peak power is at only 5200, and should be closer to 5600.

What is also puzzling is that switching from pump gas, 20 psi with 18 degrees of timing over to race gas, 25 psi with 23 degrees of timing only gave me a 2 MPH gain at the track. So there is definitely a 'wall' that I'm hitting.

My car is doing exact same thing. Have thrown everything at it trying to fix it. Just did springs so waiting to try it out and see if it helped.

 

[20psiofevil]

I swear it sounds identical to an ignition issue I was having. Sucks you are still battling this issue. Let us know what you find on back pressure results.

 

[V6POWER]

too many--Is your battery voltage OK?

 

[toomanymodz]

Yes, battery voltage is usually in the low to mid 13's. And someone asked about the cam... yes it was properly degreed-in by the builder.

 

[we4Mateo]

Yes, battery voltage is usually in the low to mid 13's. And someone asked about the cam... yes it was properly degreed-in by the builder.

I've seen lots of cams put in to what the builder wants and not necessarily what the cam manufacturer recommends and the setup suffers. If you don't know how it was installed, to the degree, find out and compare it to recommendations. Did Weber do the cam install too? If so, you're probably fine; otherwise find out for sure. Still sounds like a valvetrain wall or still ignition related. Do you have your CCCI hotwired?

 

[toomanymodz]

Yes, Weber did the cam install, so we're good there. I don't have a CCCI hotwire. Here is something interesting: last year I upgraded from PAC 1200 to 1201 valve springs and the RPM wall went from 5500 up to 5850. Fast-forward to last month, I checked the installed-height and it was 1.800 instead of 1.750, which equated to 30# less spring pressure than spec. So I shimmed to the valve springs, and much to my surprise, the engine only gained a few RPMs, so the wall is now 5875. Valve lash is 1/2 turn. I agree that this sounds like ignition or valve-train. I will still do the back-pressure test though.

 

[we4Mateo]

Yes, Weber did the cam install, so we're good there. I don't have a CCCI hotwire. Here is something interesting: last year I upgraded from PAC 1200 to 1201 valve springs and the RPM wall went from 5500 up to 5850. Fast-forward to last month, I checked the installed-height and it was 1.800 instead of 1.750, which equated to 30# less spring pressure than spec. So I shimmed to the valve springs, and much to my surprise, the engine only gained a few RPMs, so the wall is now 5875. Valve lash is 1/2 turn. I agree that this sounds like ignition or valve-train. I will still do the back-pressure test though.

Good luck and let us know. Sounds like you're getting towards the conclusion. With real aggressive lobes, you may need more spring yet?

 

[toomanymodz]

They're not aggressive lobes, so the current spring pressure (140 seat) should be sufficient. I did the back-pressure test and at 21 psi boost, the exhaust pressure was about 30 psi. I talked to Pete at Precision and he said that I could try using a .85 A/R exhaust housing instead of my .63. That could help with the top-end power, with a slightly slower spool. At the track, the current combo spools a bit too fast and blows off the tires almost every time.

 

[we4Mateo]

They're not aggressive lobes, so the current spring pressure (140 seat) should be sufficient. I did the back-pressure test and at 21 psi boost, the exhaust pressure was about 30 psi. I talked to Pete at Precision and he said that I could try using a .85 A/R exhaust housing instead of my .63. That could help with the top-end power, with a slightly slower spool. At the track, the current combo spools a bit too fast and blows off the tires almost every time.

I doubt the housing change would make a difference at those pressures. There's a lot left in what you already have.

 

[GetOwnedVette]

I doubt the housing change would make a difference at those pressures. There's a lot left in what you already have.

I agree...not even near 2-1 there. Should be fine. Can't wait to see what you track this problem down to...

 

[hungerbuhler1]

I swapped to the 140# springs and it didn't help much. Maybe 100-200 more rpm. If I turn boost down I get more rpm's but not much. I've thrown everything at it and cant figure it out. I guess I have to accept it as a 10.20 car and I'm not hitting 9's with it.

 

[FASTV6HENRY]

Hungerbuhler are your champion heads stock with the CNC cut on them or have they been ported and matched to your intake? I am also wondering what Cal thinks because you have more than enough to be in the mid 9s.

 

[hungerbuhler1]

They are ported and matched. He is stumped on it. We did coil on plug and still same.

 

[1fastcobra]

With that much difference in boost pressure.
I would think timing
I would dbl ck the cam timing marks
Make sure it wasn't installed a few degrees retarded
Posted from the TurboBuick.Com mobile app

 

[hotairgnx548]

I've seen lots of cams put in to what the builder wants and not necessarily what the cam manufacturer recommends and the setup suffers. If you don't know how it was installed, to the degree, find out and compare it to recommendations. Did Weber do the cam install too? If so, you're probably fine; otherwise find out for sure. Still sounds like a valvetrain wall or still ignition related. Do you have your CCCI hotwired?

Can you explain how to hot wire a CCC1? thanks John

 

[Lil Truck]

Can you explain how to hot wire a CCC1? thanks John

Caspers Electronics makes a CCCI hot wire kit.

 

[bison]

I swapped to the 140# springs and it didn't help much. Maybe 100-200 more rpm. If I turn boost down I get more rpm's but not much. I've thrown everything at it and cant figure it out. I guess I have to accept it as a 10.20 car and I'm not hitting 9's with it.

I'd look at the valve train again. What installed height and part # spring did you use?

 

[norbs]

What cam is in this car? The one in your sig? If your making power to 5850, Id say its not the springs, but maybe the cam spec is too small and you results are normal..

 

[hungerbuhler1]

I'd look at the valve train again. What installed height and part # spring did you use?

I'll find out for you.

 

[toomanymodz]

What cam is in this car? The one in your sig? If your making power to 5850, Id say its not the springs, but maybe the cam spec is too small and you results are normal..

Yes, cam in my sig. I've heard others getting 6400 with this cam (although way past the power peak, it'd still rpm up there). Perhaps I should've gone with the 224/224.