Bouncing tach tip
 

I know that there have been many threads about this, but just thought I'd pass this along.

My tach would constantly swing all the way up, then all the way down before returning to the correct position. I would constantly watch my volt meter to see if I could see any spikes or drops, but never did. Although I didn't see any other signs that my voltage regulator was bad, I replaced it with a NAPA solid state VR (part# VR503SB) for about $24.

I put it in yesterday and went for a good drive. I noticed that the needle on my volt meter shakes a bit more at idle, and I did see one or two slight jumps on the tach (like 1-2k) but no more wild swinging needle. Plus the car felt like it had more power, although I couldn't guarantee that it has anything to do with the new VR.

Nice to get rid of those annoying little problems.

the Crane trigger you just installed probably helped also. A bouncing tach in my car was always an indicator that the points were off.

That's one reason that I did these two mods one at a time. I did the VR first, and that seemed to do the trick. I hoped that one of the two would fix the tach.