If you are using the magnetic pick-up input (green and violet wires) to trigger your MSD Ignition, you will need the PN MSD8920 Tach Adapter. This adapter will correct the operation of most voltage triggered tachometers that do not work directly off the tach output terminal of the MSD Control. This Adapter should also be used on current triggered tachs (hooked in series with the ignition switch).

Product Reviews for MSD8920 - MSD