[johnechi]

Yep, either you have a holddown clamp that is either cheap aftermarket, the bolt is stripped and won't tighten, or the vacuum advance unit is shot, contact plate is jammed, or the advance weight springs have lost their temper and the advance weights don't swing out when they should. Hopefully its the clamp or a bad dizzy.

I just had a worn out dizzy in my case. Replaced it with a Mallory vacuum advance, magnetic pickup type. (pn# 4248201) Works great out of the box (stock 80s 350 4 bolt main), the vacuum advance unit is adjustable and it comes with a advance spring kit and directions if you need to fine tune it to your engine.