GM Module Triggers A Duraspark 2

GM MODULE hookup for Duraspark (and others)

Sacrilege you say! This is not a new item but it is worth mentioning because it is a quick and simple poor mans electronic ignition. It can be adapted to a wide variety of distributors.

In our case all that's required is a Duraspark distributor, an HEI module, and a coil. Because of the dwell control and current limiting circuits built in to the HEI module you can use just about any coil you want, including the TFI coil, and no ballast resistor is needed. It needs a full 12 volts to function. The module you want a GM 4-pin early HEI. (GP Sorenson EL102) They came on GM vehicles from the mid seventies through the early eighties.

There are four pins labeled W, G, B, and C. The G pin is a 3/16 inch (0.187 inch) male quick disconnect and the rest are 1/4 inch (0.250 inch) male quick disconnects. The unit is grounded through the mount holes so make sure you have a good bite here. The HEI module gets pretty hot and needs a heat sink to carry heat away from it. A simple square of flat stock aluminum works for me. There are two locating pins on the back of the module that you will need to eliminate so it will sit flat. Also make sure to use the heat sink compound supplied with the module to assist in the heat dissipation.

The wiring is very straight forward. The distributor hookups are W+ and G- and the coil hookups are B+ and C-. That's it!

GM HEI Module


The hookup for the Duraspark distributor is equally straightforward. You can use a salvaged 3pin harness connector or simply use common 3/16" and 1/4" female quick disconnects. W is the orange wire, G is the purple wire and black is the ground. This unit needs to be grounded and a common ground back to the GM module gets the job done nicely and ties it all together.

The TFI coil, is the square looking coil used on fuel injected Fords. (Advanced Auto - GP Sorensen P/N GC-407) .Once again we are in the economy mode and this is a easily acquired part. The Ford TFI (Thick Film Integrated) coils advantage is that it puts out about 2 1/2 times the usable spark energy of a typical round type coil. Plus it can be mounted in almost any position, even up side down. Switching to the TFI (Thick Film Integrated) coil will effectively double the usable spark energy, and can be mounted in any orientation. The only issue is that the TFI coil uses a different type electrical connector and distributor wire connector. It also uses a locking connector for the coil wire. Easily fixed with new cable ends. (TFI connector - Conduct Tite #85121)

As mentioned before you will not want a ballast resistor. The ballast resistor added series resistance to limit current through the coil. The HEI module actually senses the current internally and compensates to prevent excessive current draw. It's there but you don't need to worry about it.

Reference article here