Weav's Vet

I took my car to the dyno yesterday. It absolutely sucked! It was down to 277 rwhp from 303 on my last pull before the cam I installed. The torque actually gained a little over my last pull before the cam. up to 310 from 3.07.

To top it off I just made one pull because the car refused to start or do anything after that pull. I'm assuming it was VATS but I don't really know for sure yet. The PCM may have just died on me. I put and extra PCM I had in the car and it fired right up. I got it home and I'm in the process of taking this up with my tuner. He says it probably isn't the tune making it run so bad that it is the motor. I disagree because it ran pretty damn good before the new cam. What do you guys think?

Just to refresh.......1996 LT1
The CPS has been deleted on the car.
The cam is a LE 226/230 .565/.565 111 lsa
The motor is stock and has 95K on it.
The rear gear is 3.07
2800 Pete K stall
EWP
1.6 rr's
Patriot extreme valve springs
New GMPP lifters
Hardened push rods
Guide plates
Double roller timing chain
New GM opti
New MSD 8.5 wires
52mm BBK TB

PLRX

No way, 277 is like a stock LT1.

Mike, did you re-tune the ECM?

Weav's Vet

Tell me about it!

I had it retuned.

Weav's Vet

I should get the dyno file today. It looks more like a EKG than a dyno file. Very jagged. AFR was lean up top.

383vett

How lean was lean? Was the cam degreed in?

Pete K

The cam is my first thought. Not that I nescessarily think it is off, but degreeing it will allow us to eliminate it as a possibility.

Weav's Vet

Didn't see the exact number I was going by what the operator said. I'll post the file when I get it.

I asked LE about degreeing it Pete. He said the advance is ground in and it would be close. I realize degreeing would probably get a few more out of it but I didn't pull the engine and it would have been difficult with it in the car.

Pete K

Assuming the factory crank key is in the correct location, the timing chain was drilled properly, and the bolt pattern in the cam snout was drilled correctly, it "should" be ok. If anything I just mentioned is off, so will cam timing. The main reason I degree is to eliminate the possibility of some manufacturing process with these parts. 2x I have had a major problem, and caught it with the degree wheel.

MK 82

Exactly! Degreeing confirms what is on the card.

Weav's Vet

I see what you guys are saying and that is why I asked LE about the degreeing but I'm leaning towards the tune until that has been eliminated then I will look elsewhere. That PCM just never seemed right.

Let me ask you guys this. Would it be of any advantage to me to have a dyno tune done on the other stock PCM I have at this point? Would that show that the cam is off?

Pete K

I do agree that you likely have a tune issue.
Worry about valvetrain later.
Another possibility is a mis-boxed cam. The tuner could have tuned for a cam, based on your specs, but the cam in the car can be wrong compared to the cam card. I had this happen with a TPIS cam years ago. I bought a small cam, but the dial indicator and degree process told me it was a much bigger cam. Glad I caught that too.

Weav's Vet

Another thing........how could the stock PCM run as good as it did with the CPS not working? I was really surprised it ran at all. Granted it was rough as sh*t but it ran decent. Just gobbled up gas.

JAKE

I can't see how re-programming the other PCM would tell you anything about the phasing of the camshaft.

Based on what you've writted, I'd first address the lean condition; trying to find out why it's lean. It could the be the programming, but it could also be other factors like the fuel pump, partially clogged fuel filter, injectors, fuel pressure drop off, etc.

Are your heads still stock?

Keep us posted.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!

Weav's Vet

Thanks Jake

The fuel pressure starts at 42 and drops down to 40 after running a bit. Holds and actually increases whe the car is shut off. The fuel filter is less than a year old and the pump also. So are the injectors. 24 lb Bosh EVI High Performance from Jon.

Yes, heads are stock except for the springs, guide plates and studs.

MK 82

I assume you mean Crank Position Sensor. That only comes into play with misfire and is informational only.

Weav's Vet

Yes, that is what I meant. Thanks for that.

MK, remember that thread I had about race fuel?
http://forums.corvetteforum.com/c4-t...race-fuel.html

Is it possible I have a cat issue? I had to replace a forward O2 to get rid of the code I wa getting. I never checked the cats out though.

pianoguy

Sorry to hear, Mike - hope you get it sorted out soon!

pologreen1

man if you got the wrong csm i hope they work something out with you for all the troube.
good luck

STL94LT1

I'm betting it's not the tune. With your mods the stock tune would run decent at WOT.

pr0zac

i had a similar problem. i had 3 burnt spark plug wires..