[jims68ragtop]

I have a 1970 Firebird 400 engine that has been rebuilt - Edelbrock aluminum manifold - Edelbrock 750 performer carb. It is in a '68 Lemans factory 4-speed. The engine is built up to around 400 hp by being bored, beefy crank and cam, and ported heads. The trans has also been rebuilt. The car starts and idles well. Acceleration is great. Dwell, timing and rpm are properly set. The car jolts or misses when trying to run it at an even speed at 30 to 40 mph. Runs great at 50 to 60 mph. The only main parts remaining from the original 350 Lemans engine is the generator and the distributor. Any ideas on the jolts and misses? Thanks.