I have a 74 Z28 with a 70 LT1 powering it. For awhile now the tach has been bouncy. It seemed like bumps in the road caused it to bounce at first but then it randomly jumps quite a bit when your get it throttle. To add to it recently Ive noticed on start up it goes crazy at idle unless I press in the slack on my clutch which also brightens the interior lights. I don't know if this all stems from the same problem. Help!