LS1 Where to check?

[Transam388]

I have a 98 T/A with the following mods. I was expecting a LOT more power and on the last dyno run they said I was down at 366! I do have a 150 of nitrous but without I figured I would be closer to the 390 zone. No codes shown except for an occasional Evap Emmisions Small leak code. Possibly looking at a leak down test. I had a place try to figure it out and they said it seemed to be leaning out on the top end. Just not sure what is not happy in there. :dunno: Any ideas are appreciated! :help:

98 LS1
FLP Long Tube headers / high flow cats
Borla Cat back (Running open)
Morgan Motorsports ported / polished Throttle body
Granatelli MAF
Sun Coast Creations Ram air system.
K&N air filter
LS6 intake
30 Lb SVO injectors
Custom tuning (LS1 Edit)
Stage 2 Heads (Which I think may be crappy)
Crane 1.8 roller rockers
Cam but off the top of my head I don't remember the specs. Fairly mild
3.42 gears
Auto trans with a 3000 Yank stall convertor
Underdrive crank and underdrive power steering pully's
Throttle body bypass

Thanks for any ideas! Just try not to laugh to hard at my mis fortune! OK, go ahead! :lol:

[YoMommasTA]

who tuned it?

[Transam388]

Originally tuned at MTI and then at Horsepower Engineering in Houston. HPE made some other changes which got the motor running better but they where the ones who said it was leaning out on the top end but could not figure out why. At the HP the stock fuel pump should still be OK and it always says 58 to 60 PSI on the guage.

[YoMommasTA]

have a leak down and compression test done.Its a sure way to know what to expect from the engine.

[hammertime]

You have three potential issues that I see:

1.) Without knowing what cam you have, if its small in your words, it may not be enough to reach your goal.

2.) If you are lean, what is the a/f ratio, you may need some enrichment to make power

3.) You are running an auto with a stall converter, both of which soak up energy and turn it into heat. Slippage from a stall is known to drop your power readings as well. What is the inlet air temp reading on your dyno runs. Ram air doesn't work so well in a stationary car.

Also, whose heads and why do you think they are crappy?

Overall, I'd say make sure your a/f ratio is where it should be, and you may not be all that far off. Racing dynos is fun, but your really after realworld performance I assume.

[Transam388]

Cam is
Valve lift .523 intake .528 Exhaust
Duration at .006 Tapet lift is 267 intake and 271 exhaust
Lobe separation is 112.0
Lobe lift .3080 Intake .3110 Exhaust

The cam was supposed to be a slightly more agressive than stock since it is driven daily but I want to change this out. I also did not want it to high since I have the 1.8 rocker arms which I may also move back to 1.7 and use shaft mounted and a more aggresive cam. As far as the heads being bad I have my suspicions and from what I have heard others have as well. The heads were done by a guy named Dan Moffis who apparently also is AKA "Dyno Dan" and that some others have had issues with heads he has done for the LS1.

Thanks for the info though it always helps!

[MadSeason]

Ditch the Granatelli MAF and work on your tune, those aftermarket MAF's have resistors in them that screw up the tune. You injectors are also overkill right now, go back to stock and sell them for mod money. 98's came with bigger injectors anyway. What kind of compression are you getting with your heads? 366 with cats, an auto, and stall seems right with your mild cam, but I think you can tune it out for some more

[BIG D's SS]

WIth my mods I got 355 rwhp and 360 tq with mods and and 90,000 miles.

[MadSeason]

Something else I'm wondering, was it a Mustang or Dynojet Dyno

[Ed Blown Vert]

Also was the converter locked or unlocked?

[Transam388]

Well I must say from what ya'll are saying I am starting to feel somewhat better! So on the MAF not using the Granatelli, just go back to a stock or what kind? As far as compression with the heads I need to get that checked. The Torque convertor is a Yank 3000 with lock up. Again, thanks for all the input on this. It is the real world info like this that I find the most helpful!!

[Ed Blown Vert]

Right, but did they lock it on the dyno? My guess is they didn't.

[MadSeason]

Well I must say from what ya'll are saying I am starting to feel somewhat better! So on the MAF not using the Granatelli, just go back to a stock or what kind? As far as compression with the heads I need to get that checked. The Torque convertor is a Yank 3000 with lock up. Again, thanks for all the input on this. It is the real world info like this that I find the most helpful!!

Just go back to stock MAF