what's goin on?

should I put on the aftermarket universal tach?

ea82 carb

Jumpy tach is usually a sign of wear on distributor bushings.

Yeah,

 

What Caleb said! Have it re-bushed.

Bad coil can mess with your tacometer also. Might start there

it suffers the symptoms when the lights or blower is on, otherwise it is fine :banghead

this is not your typical jumpy tach

bump for the day crew

Try adding some extra grounds in the engine bay.. My car was doing some odd stuff when the lights and blower were on.. all went away with the addition of a couple of battery to body and engine to body ground wires.

finally I admit I agree with you

Had to happen eventually