Can anyone give me any advice on how to fix/check to see what's going on? Someone told me the tach on the 68 was vacume operated which doesn't make sense.

Thanks.

I have a 68 Camaro and use the tic toc tach. It is not vacuum operated. It uses an analog electrical pulse to move the tach needle. These tacs are finicky if you convert to electronic ignition, but generally work fine with a conventional, point-triggered ignition. You can buy filters from all the resto places and online performance sites, like Jegs, Summit, Accel, etc. If you call the tech line at Year One or Classic Industries and tell them you purchased one of their tic toc tachs, they can walk you through how to test it. The signal wire feeds off the negative side of the coil. You want to make sure you are getting pulses on this wire when the engine is running. If the tach is getting some pulses, but not operating, the tach is bad. It is usally a filter problem when the tach is operating erractically.