MSDIGNITION Ignition Coil - HEI Distributor Coil GM HEI HEI Coil; coil; Internal coil; GM coil; MSD Ignition Coil - HEI For GM HEI Distributors The MSD HEI Coil is designed for use with the MSD High Output HEI Module, PN 8364. It will work with stock ignition modules, but for maximum output use the MSD HEI Module. HEI owners now have a choice to replace their stock coil with the MSD High Energy Unitized Coil for GM HEI Distributors. This coil is a direct replacement of the stock coil and offers increased spark energy when used with the MSD HEI Module, PN 83647. Recommended for use with MSD HEI Module PN 83647 Direct performance replacement for GM HEI coil-in-cap distributors 70:1 turns ratio and lower primary resistance produce high voltage output Full power sparks to 9,000 RPM when used with 83647 MSD HEI Module CARB E.O. Approved