BLACK Z

Hi, Okay hopefully you guy's can help, I have had no luck at any of the local garages and dealers (yes I have also tried to fix the problem myself many of times). I have a 1986 Z28 camaro, it had a 305 lg4 and a auto from the factory, It now has a gm 350 replacement motor and a wc t-5 (the t-5 was behind the 305 for awhile). When ever I am decellrating and the rpms are above 2,000 I get a constant after fire thought the exhaust, if I give it a little bit of gas it will clear right up. I can sit and rev it up and it will not backfire once, it will not do it while I shift either. The motor runs great, the only mod I did to it that the 305 did not have is a edelbrock performer intake and the msd 6al. I have tried disconnecting the 6al and it still does it. I also had the carb rebuilt ( it is on the car now). I have tried a jet perf stage 2 carb and still no change. I currently have there stage 2 chip for a 305 in the car. I did change the knock sensor and the module over to the 350 pieces. The car is in perfect shape tune up wise. People tell me that is this is normal for carbed motors, but the 305 never did this, and I also had a summit 350 in the car before this and that motor never did this It had a 650 double pumper and a vac advance dist. If you could please give all the help you can it makes me want to sell the car.

Air_Adam

Sounds like either the carb could be running somewhat rich, or maybe your cat is toast? Mine did that a few times, and a simple carb tune cleaned it up.

demonchild

the popping from the exhaust is usually unburned fuel in the exhaust igniting (rich) or the engine backfireing from being to lean. my guess would be that your car is running to lean if you put a rebiult carb from your 305 onto your 350 because the jetting will be to small. a good indicator of how the engine is running would be to pull a plug. the plug on the from drivers side is usually the easiest(sp?) and gives the best indication becasue it is the furthest from the carb.

BLACK Z

The exaust is the same has been on the car with the stock motor, the summit motor and the New motor, The whole air pump system was new, and it was doing it so I took it off to see if that was the problem and it is still doing it, so I just left it of. The cat was gutted on all 3 motors and I have since taken it off and put a straight pipe in it's place and it is still doing it. The thing is it never did it with the 2 other motors never, and the summit motor had a lot more pwer then the current one.

P.S I have replaced all of the gaskets on the exuast and went over it a bunch of times trying to find a leak.

Is there a good carb shop that you guys have a link or a # 2 that I can call? thanks

88 350 tpi formula

iTrader: (9)

what cam and comprestion are you running in it now vs before? just kind curious

BLACK Z

I am not sure on teh specs, of the new motor it is a stock GM 350 replacment motor,