ONESLOWZO

I have a 99 T/A with a built motor big cam turbo 400 nitrous car 300 hit.. I am totally lost as to why this problem is occuring. Down low the car runs great all the way through first gear right until im about to shift in to second (6500 or so rpms),, Then boom a back fire and the car shuts down. Ive checkd plug gap fuel pressure, pushrods broken valve springs. pulled the intake off no cracks nothing seems to be wrong.. Does anyone have any ideas or has had the same sort of issue.. This is occuring both on motor and on the spray. Thanks for all the help

bigboykilroy

iTrader: (48)

how was the cam lined up? Was there any advance ground into the cam? It kinda sounds like the valve is floating on you at high rpm. do you have hy lifters or solid ? if adjustable rockers what lash do you have it set at? Is there a RPM limiter of any sort as well? Not assuing just gathering info here.

andrew69_04

iTrader: (148)

yeah, you dont have some sort of rpm limiter still in the ecm that could be causing this? fuel cutoff?

ONESLOWZO

stock lifters rockers and patriot gold double springs, I have no idead about the cam stuff i bought the car already set up.. rpm limiter is at 68 im shifting way before that..

bigboykilroy

iTrader: (48)

Adjustable rockers? Can you change the RPM limit to say 7500 and see what it does? Just to take that out of the equation. shift at 6500 and rev at 6800 is close. Do you happen to have any video of it doing it?
Are you using all stock pcm, ignition, external retard, crank trigger etc. If you have a HP Tuners File or LS1 edit post it up sp we can have a look at it, to see if its possible someting in there.