I fired up my newly rebuilt 383 and it starts right up but... Feels like it is missing and vibrates erratically when I bring the RPM's up to 1,000+. I ran a vacuum gauge and it is steady at 21. I have verified spark at each plug and fuel pressure is set at 40 psi. My next option is to re-check the valvetrain, verify all valves are functioning properly and maybe reset valve lash.

The PROM was excessively rich so I adjusted the lower VE table to get it closer and it has smoothed out some but I'm not comfortable runnning it like this. The assembly was balanced so I know thats not it. I have no leaks (now) and no other noises, just feels like it is missing on a cylinder.

Its a 383 HSR with AFR 190 heads, CC 230/236 dur and .544/.555 lift. Cam installed straight up.

Any ideas would be appreciated... In the meantime I guess I'll go pull the valve covers.

 

There's a long list of things that could be at the root of the problem.
Faulty injector, blown head gasket, air leaks, bad plug, bad plug wire, loose rocker stud, broken rocker etc etc.
On an engine that I worked on recently, I had the same problem, and I checked everything including changing the pushrods because some were bent about .010"
Finally tore down the engine to find it was a cracked block.

 

Well I think I have it figured out. Everything is new, but I double checked everything I could think of and went ahead and kept adjusting the VE tables anyway. It seems to be smoothing out. I worked mostly on the lower VE table yesterday and have got it idling a lot better. It was way rich, to the point of making me think there was something mechanical wrong. I guess I should have posted in the DIY PROM forum. I never saw so much black smoke pour out the exhaust before!