I just installed my new engine, and it only Dyno'd 350 RWHP & 350 TQ, and I was shooting for at least 420 HP N/A. The set up: Bored .020" over, forged rods (manly sportsman) & pistons (srp), Balanced, Stock crank (nitrided), all parts cryo treated, Full stud kit (mains & heads), Fully ported AI heads, GM 847 ish cam, comp pro mag 1:6 RR's, stock intake, stock TB, stock MAF (un touched W/screen) Hooker LT's, 3" home made y-pipe, SLP 2 OTL, Weldon fuel pump, dial a flow, -8 feed line -6 return @ 42 PSI, 36# delfi injectors, LT-1 edit. We (dyno Steve, Phil, and I thought it was a restriction because the MAF maxed out at 312 GMS @ 6100, and the MAP never exceeded 89 KPA (85 KPA Average) the AF was 12.7. I wanted to know if there is a way to pin point the largest restriction and work from there.

 

What's the compression ratio?

What did the heads flow and up to what lift were they flowed?

What's the max lift with your cam (you said 847-ish)?

How kinked is the homemade y-pipe?

And lastly, post your dyno graph with power and a/f mixture.


________________
Rob
1994 Firehawk#319
11.83@120.61
Slightly Modified
1996 Blown V6
2002 Trailblazer
San Diego F-Bodies
"Garp bit Bonky."

 

Put a vaccum guage in front of the throttle body and another on the intake plenum and see what both give you for readings

 

The CR is 11 to1, the heads peaked at .650 lift, the cam peaks at .625. What do you mean by Kinked? The Y-pipe is 3" all the way through, and the merge point is smooth, it's not like a "T" it like a "Y". I will try to see how I can hook a vac guage in front of the TB. Also what should I be looking for from the 2 vac guages? Could you give me a possible senario, maby an "if, then" statement.

 

We need to know what the heads flowed, and what duration the cam has... Mainly though what the heads flowed... That will make or break a setup. Even if they look all pretty and nice, they could be the worst flowing heads that ever were. So post up the flow numbers and cam specs...

Chuck

 

most of the guys with AI LT1 casting heads on this board have made over 400rwhp on a stock bottom end , so the heads are probably not the problem.

 

You are not in the WOT tables at 89kpa you need to hit 95/100 for WOT..

Stock TB? need to up to 58mm
12.7AFR you can still go to 13.1AFR
What is your timing...
What is your tps at wot ( voltaqe )
the MAF last on the list ....for hurtting power right now
you should be spining the eng to 7000rpm and see where it drops off

 

I bet Phil's gonna take offense to that. His heads have an impeccable reputation, and are among the best that an "average joe" can get his hands on.

 

Calm down, I was just asking a question and making a comment. I know nothing about the heads or AI's reputation. So I'm sure by what you guys are saying, they're pretty good..

Later,
Chuck

 

Phil has all my confidence, I am positive the heads are as good as they can possibly be. We spun the motor to 7100 RPM, and it rolled over at 6500. I don't exactly remember where the timming was but I am willing to guess 38 degrees or there abouts. The air fuel ratio was not able to go leaner. We deliberatly tried to make it go lean, but it wouldn't. I don't know where the TPS voltage was at, but we did check the throttle position manualy, and it was moving well within it's range.

 

Are you sure you are getting the throttle open all the way? I've seen it happen more than you'd think!

 

This whole discussion has been general engine troubleshooting... I don't see at this point why this is in Adv Tech. Transfering to LT1 Tech, thank you.

 

Auto or manual? If it's an auto with a loose converter there will be a significant difference in rwhp. I do agree though that 312gm/s is too low as is the MAP. I'll think about it.

Rich Krause

 

The only thing that can cause such low AFGS readings on the MAF, make no power & peak at 6100 is your prolly running Comp R' lifter & went more then ZERO lash, basicly I would have to bet your valve train is adjusted too tight, this will cause you to max out your readings around that RPM & make no power.

 

The car is a manual. I am running the comp R lifter, I set them at zero lash + 1/2 turn. I still have some valve train noise (in spots, I think 2-3 rockers are ticking very slightly, and I was going to check their adjustment. By saying "zero lash" you mean to take all the play (up & dn) out, and then tighten the set screw?