We analyze 10 common myths regarding HEI (High Energy Ignitions) distributor system including ones regarding internal coils, billet housings, performance gains, vacuum advance, and plug wires ...

Originally, the HEI system was fitted with a four-pin module. By 1978, it had a five-pin unit. Seven and eight-pin modules were more a computer-controlled element that came around in the 1980s.

With the electronic HEI module mounted inside, and the coil in the cap, the Davis distributor needs no external extras to work. Just a hot 12V wire in, and it's ready to run.