where is the tach wire in engine compartment.

should be in the harness going to the coil.

what is causing my tach to bounce?

From what I've read it's the tach itself.

What part of Arizona do you live in? I live near Show low. Be nice to have another local teener.

Chino Valley.

Could also be the points, condensor, distributor ground, or wiring. But the tach itself is the most likely problem.

--DD

Purple/black from tach to 14pin on relay board from memory,don't know if it stays that colour from engine 12pin harness to coil .
Check the connection/condition of the wires at as many points as you can also check you a good earth on the back of the tacho and have full 12volts going to it (red/white wire).
Failing that get it repaired or fit good secondhand one, the cost to repair could be up there.

Thanks for all the info guys, I'll check it all out tomorrow. I really like 914world for all the great input i get back, thanks. oh, I'm not using points.