The V8 coil is built into the distributor cap, and it's unique to the system. The only remote-coil GM HEI's were for some early 4 and 6 cylinder engines. It has a VERY low resistance in the primary circuit, resulting in a massive surge of current and a quick buildup of magnetism as the power transistors in the module begin to conduct- - - -hence the necessity for a current limiter when the magnetic field reaches the full-saturation point. The open circuit voltage output is a minimum of 25 KV and can go to 50 KV under ideal circumstances. That's the reason "HEI" stands for "High Energy Ignition". Since a clean, properly-gapped spark plug fires at less than 10KV under normal operation, HEI equipped engines will run almost as well with the ground electrodes completely removed from the spark plugs. Aftermarket knockoffs are usually a thin shadow of the original parts- - - -Look at Edelbrock VS real Carter AFB carburetors!
I taught automotive electricity for a little over 30 years.
Jerry
