GM HEI control modules

Road-race engines and ancillaries - general discussion
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Joined: November 30th, 2006, 10:09 pm
Location: Kingsport, Tennessee, USA

GM HEI control modules

Post by turbofiat » December 1st, 2011, 9:58 pm

I realize these parts fit American cars but they may have been used on cars outside the US. I don't know.

This first module was used on a variety of cars (GM, AMC/Jeep/Renault, Peugot, Fiat's w/Marelli distributors just to name a few).
4 pin.jpg
4 pin.jpg (10.52 KiB) Viewed 2122 times
This module seems to be a common retro-fit for any distributor that uses a magentic inductive pickup such as Marelli, Bosch, Ford Duraspark, etc.

I finally learned a simple way of retarding the ignition timing 10 degrees under boost. There is a 5 pin module similiar to the 4 pin but has a tiny connector when grounded will instantly retard the timing 10 degrees.
5 pin module.gif
5 pin module.gif (86.56 KiB) Viewed 2122 times
This module was used on 1980 and 1981 Pontiac and Oldsmobile V8s. Supposably the reason behind this retard function was these engines had high compression engines and were easier to start with the ignition timing retarded 10 degrees. I also seem to think it prevented detonation under wide open throttle because it was controlled by a vacuum switch. I'm my case, I'll be using it to retard the timing under boost.

This should be a "drop-in" fit for 2000 Spiders and 131s using the Marelli distributor since it was designed to use the 4 pin module to begin with. Last night a quick test fit of the finned coil unit shows a tab may needed to be grinded off to clear the pickup connector.

But before trying this with my Spider, I'm going to be trying this on Yugo's Bosch distributor this weekend. The ground will be triggered with a pressure switch.

There are other AC Delco 5 pin ignition modules but I won't discuss them.

What I'm wondering about is the 7 pin module shown here:
7 pin.jpg
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This particular module I believe has the ability to vary the amount of retard by varying voltage or resistance to one of the small five pins. Like the 5 pin module I will be using, I believe the leftmost pin on the 7 pin module has an "R" above it which would indicate it's some sort of retard function. I believe this module was used on vehicles with distributors without centrifical or vacuum advance systems. The amount of advance was controlled by an ECU which was determined by a MAP sensor and also a knock sensor. But I'm not sure.

Everytime I search for information on how to wire this module up, it points to Megasquirt or Megajolt. I know there are some people on this board with experience with Megaquirt systems. I was wondering if anyone had an experience with this type of GM module.

I hope I don't sound too "old school" but all I want to know if it's possible to wire this module up without using a Megasquirt controller and to a distributor with a magnetic inductive pickup and centrifical advance and be able to adjust the amount of retard using a potentiometer rather than a computer? I seem to think the 7 pin module is triggered using a HALL sensor instead of a magnetic pickup.

124 Spider, Yugo,131

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