GM HEI Module Install

Installing a GM HEI Ignition Module into a 1976 280Z (which already had a ZX ignition)

This article describes how to upgrade a ZX ignition module to a GM HEI module. In this particular case, the ZX ignition module happened to be installed in a 1976 280Z which had been upgraded to a ZX distributor/ignition module using the Atlantic Z Club instructions. The purpose of the HEI install was to fix a sudden engine cut-out problem and a jumpy tach problem.

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Heat Sink

The first thing I needed was a nice heat sink and, afters scouring the basement and considering attacking an old Western Electric telegraph test set with a hack saw, I laid eyes on a stack of these:

Which is an old tape format from the 80's/90's (we called the streamer tapes back in the day). I still have a SCSI drive that can read/write these things (but haven't tried in at least 10 years)... Anyway, these tapes are build like tanks, the back plate is .1 aluminum - I knew I saved them for a reason. The following pictures illustrate the transformation of one of these tapes into a nice heat sink for this HEI conversion project.

Add some quality time with a hack saw and drill to get a nice heat sink...

Don't forget to use heat sink compound (I used the stuff my module came with). Note to self: add part numbers here.

Disconnect the old Ignition Module

Pull the distributor and yank the old ZX module (this 76 280Z had been given a ZX upgrade by PO). I figured the neatest way to do the job was to open the old ignition module case, cut the connections, and jumper the distributor wires to the external connections (note that I misapplied some opening force to the old module and had to glue it back together - this was not necessary - observe that access to the guts is not at the bottom but at the top - see photos).

Pull the distributor then disconnect the distributor wires from the old ignition module: two spade connectors - a gentle yank with some plyers should do it - clean the connectors/terminals while you are there - I sprayed a little DeoxIT and worked them on/off a few times. Pay attention to which side the wires go to (but the rubber boot they plug into is marked red/green if you forget). Remove the two screws that hold it to the distributor.

Disconnect the old module and crack it open (I did this a little too literally)

Clip off the connections to the board, then jumper the posts as shown. Clean the posts then you will need a lot of heat (I used an 800 deg F iron, nicely tinned and laid into the post and wire for a good 10 seconds before applying rosin core solder). What is that goop in there?