Finally some time to reply...
Finished up swapping the engine out. Bone stock motor with the same intake and injectors. Still had the lean spike and still had the big KPA fluctuations. Looking through my tune I noticed I forgot to change my injector timing back to stock, as it was changed to match my cam values. Changed it back to stock and BLAMMO! No more lean spike. I tested it at least 20 times, and I am 100% sure injector timing was the issue. I can change it and make the lean spike happen, change it back no spike. So glad I got that ironed out.
But the KPA dance was still there. On a bone stock motor. Not a single part in the valvetrain was common between motors. So on a longshot i tried something.
Here is my stock V6 air intake on that V8 motor, with a stock intake. It does have the V8 MAF and tube, but that is the V6 hat. I started looking at this because my WOT KPA indicated a restriction somewhere.
So on a drunken escapade I grafted an 03 Cobra JLT intake I had laying around as a spare to fit this truck. This is a 4" cold air. And I had the BIG 5 wire MAF laying around from my LS swapped S10 blazer that blew up due to a lifter failure.
Here is what I came up with:
And holy hell.....what a difference it made. I now hover around 100kpa WOT. Truck feels a lot more powerful, gas mileage went up damn near 8mpg, and everything ironed itself out I was having problems with.
I swapped my cam and fixed heads back on it yesterday and truck runs great. Absolutely a totally different engine now. I rented an hour of dyno time today and it put down some damn good numbers too. 389hp/422tq, and those are corrected numbers on a dynojet.
So moral of the story is dont screw with the injector timing on these motors, and do not run cheap valve springs. Causes weeks worth of headaches.
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