Whats the difference between a mechanical and electronic tachometer?
A mechanical tach works much like a speedometer. It uses a gear drive, usually off the distributor, and a cable. These were used on very early electronic ignition systems in the late 1960s and early 1970s. There may have been other applications that I am not aware of. An electronic tach uses a signal from the secondary or negative side of an engine coil. There are no moving parts, just wires and the tachometer itself. These are usually very reliable. For your Regal I would certainly use an electronic tach. There is a Tach lead on the distributor cap that you can use as a signal wire. It is marked Tach on the cap right next to the B+ lead.
