I have recently replaced my non working 1968 tic toc tach ( never worked since owned ) with a OER brand tic toc tach from Summit racing. Several years ago I replaced the printed circuit on the cluster due to a burn/short on the tach portion of this printed circuit. Replacing the printed circuit failed to make the factory tach work so I assumed whatever burnt the board also fried the tach . I had an aftermarket tach I mounted on the column and was satisfied with it until I decided to replace it with the new OER unit several weeks ago.The replacement tach also did not work which summit replaced with another which also doesn't work. I'm getting tired of pulling the inst. cluster in and out ! I am running a small cap speedway motors HEI ( pointless dist) with an external coil and my column mounted tach works just fine. I have done some internet research and have asked Summit for some guidance, Summit says I need a CIN SN 20 adapter. The internet sources say I need a MSD 8910 adapter? My needle doesn't bounce nor is it erratic ,it doesn't move at all. I have verified the brown tach wire from the engine comp. to the harness plug, I have verified the harness plug-in connector to the tach screw on the printed circuit board. Does anyone have first hand input that will solve,or shed light on this issue ? The internet says I need to trick the tach into thinking I have a points dist. ?? thanks
According to this vendor, the adapter needed depends on the manufacturer of the HEI ignition system you are using on your 1968 Camaro:
https://www.thepartsplaceinc.com/product/1968/1968-chevrolet-camaro-tic-toc-tach-gauge-5500-rpm-327-350-gm-6468713/56424