[Jim Sims]

I agree with early_S_man. It is likely the points. If you ignore it, it will get worse (more tach bouncing) and then the engine will start to run like hell. Plus you can burn the points. We have a 73.5 and 76 and a bounching tach means time to get the dwell meter out and adjust the points or if you put it off long then replace the points! If the points have a lot of miles on them (10,000 miles plus) I'd just go ahead and replace them as they're inexpensive. Cheers. Jim