Hey everyone. I havent posted here since I had my Firebird, but I have a question about my buddy's 94 Z28. He rebuilt the motor, its a 355 with stock heads, LT4 hotcam, Borla exhaust, roller rockers, and a K&N intake. The car does not run like it should. His best 1/8th mile time last weekend was a 9.09. Last night in the 1/4 it ran a 14.6 at 96 with a 60ft of 2.17 I believe. The car pulls good up until about 4k rpm and then it just quits making power. It hesitates and stumbles really bad. Any idea of what the problem could be? I was gonna try to clean all the sensors and then I told him to get it tuned. I thought maybe it needed more fuel but when we looked in the exhaust and its black. It also smells rich. I dont know what it is, but any help would be appreciated.

Thanks,
Joey

 

Did he change the springs?

 

Yeah he had new springs installed when the heads were rebuilt. We took it to the 1/8th mile again last night and it ran a 9.16. It pulled straight up to 4k and then it was like it hit a brick wall. It just pops out of the exhaust and stops pulling. Supposedly he has a good opti. I am going to check all the plug wires and we may try a fuel filter too.

Thanks,
Joey