Ok gearheads, I wondered if anyone had an idea of what my problem is. My 86 Elky has a rebuilt 305 (at least that's what the now deceased former owner said). The darn thing vibrate worse than any car I have owned. At 2300rpm + it really gets going. I suspected an engine size swap, and possbly the wrong flexplate being installed, but the block says 5.0L.

I'm really a ford guy. The last Chevy I had was a '65 Chevelle with a six, that I built a 350 for and swapped. I know small blocks, but I'm stumped.

Any Ideas??