phat_ridegt

iTrader: (1)

so im working on a buddies truck its an 05 4x4 gmc truck. we swapped in a low mile 5.3 that i put a 220r cam, and prc stage 2.5 cnc heads. also put pacesetter lt headers. currently its setup open headers because i need to get it to the exhaust shop to mate it all up. every time i start the truck it backfires like a shotgun.

i know its open headers but ive never ran into this before. I don't have a base tune in the truck because i can't even get it running long enough to do anything with it. i dont have much experience tuning ls motors. anyone have any suggestions on what to change right off the bat? stock intake and injectors for now. my concern is i'll tow it to the exhaust shop and then still wont be able to drive it home.....

2xLS1

iTrader: (25)

Open exhaust won't cause that on a cold start. Sounds like valves are open when they shouldn't be. You sure cam was installed dot to dot?

phat_ridegt

iTrader: (1)

indeed.

phat_ridegt

iTrader: (1)

so ive been talking with jim at speedinc, and he said the tune shouldnt stop it from running with stock maf and injectors. so i decided to hold the throttle open a bit and when its over 1300ish rpms, it runs fine. no backfiring at all. its picking up a misfire on one cylinder so im going to solve that first but it seems maybe the misfire in combination with the open headers is my problem......hmmmmmm