Gm HEI upgrade on a 78 280Z

[sblake01]

Just in case you're wondering where the module is located and why it has that shape, it's inside the distrubutor.

[ATTACH=CONFIG]51188[/ATTACH]

Since the module is attached to the distributors base plate, it makes you wonder why we're making a big thing about heatsinks? A simple sheet metal base on the fender by the coil should give the module enough cooling air. IMO, protecting it from water would be more important.

I've owned a GM car or two (really about 6) with some variation of that distributor. Including my present 84 Vette. Never had one fail. When I used that module in my 510, I mounted it by the coil, as you said, without any kind of heatsink other than washers between it and the fenderwell and it worked for over 5 years just like that. Edited February 12, 2012 by sblake01

[TomoHawk]

The problem of waterproofing remains.

[sblake01]

Never had any issues; heat related, moisture related or otherwise.

[FastWoman]

Shouldn't be any moisture problems, as it's a sealed module. I didn't really know whether there would be any heat issues, so I threw in the heat sink by default. Better safe than sorry.

[TomoHawk]

-I was going to start cutting the wires and one thing hit me: what to do with the current connections to the coil.

The ignition coil has a battery connection (he + pole) and the (- pole) goes to the ignition box, or in this case, the GM ignition module. It looks like if you disconnect the OE ignition box, you can just connect the GM module to the coil, leaving the other wires connected, unless you want to remove only the (-) one and wrap for in case you want to restore it back one day.

Edited May 14, 2013 by TomoHawk

[Zed Head]

When I installed the HEI module on my 76 car, I left all of the wires to the coil and ballast connected. I only disconnected the two trigger wires from the distributor, and the factory module in the cabin.

I used two jumper wires directly from the coil posts. A jumper from the coil positive to the B terminal, and a wire from the coil negative terminal to the C terminal. The two wires from the distributor, a green and a red, were connected green to G and red to W. If you have two blue wires from your distributor, you'll probably find that they are spliced to green and red inside the distributor. If you connect them backwards it won't hurt anything but your timing will be retarded and jumpy. If you find that just swap them.

I also ran a separate wire from the wide mounting grommet on the HEI module to a verified good ground. If you're positive that the screw through the mounting hole is a good ground that would be unnecessary.

Eventually I removed the ballast and made other modifications but that setup worked fine for quite a while. On your 78, you can do the same thing, the absence of the ballast won't matter. It's all about coil power control.

[TomoHawk]

So far, all I did was make a mounting plate and bolt it to the bottom screw on the coil bracket. I also bought some ring terminals and female blade connectors. Then I swapped in the MSD Blaster 2 coil I just got. The engine seems satisfied with it, BTW. I went to the AP store to get a coil condenser, but they are NLA?

I will try the new coil for a few days, then hook up the HEI module.

[TomoHawk]

According to the 1978 wiring diagram, the blue wire on the coil goes to the tachometer, ignition box, and the ECU Pin 1, and the Black-white wire goes to the ignition box and the battery (12V, via the ignition relay system.) I confirmed it using a test light.

[Six_Shooter]

You don't need much of a heatsink, if you need one at all.

When I first swapped to EFI, I retained the dizzy and used a GM ignition module, since I am also using a GM ECM to run everything. I used an ICM from an '86 or so 2.8L equipped S-10, mostly because I already had one or two of those modules on hand. I literally used a drywall screw through one of the mounting holes into the wheel well below the coil to hold it. I worked this way for a few months, before I parked the car for the winter and then converted to DIS the following spring. In the time the dizzy ICM was installed I made several hour long+ trips without issue. I would suspect that it would have worked great for many more miles beyond what I used it for. I have used these modules in GM cars for many years without issues as well.

[TomoHawk]

A little web search today turned up a new item, the Pertronix D2070 Module, GM HEI 4-Pin that is supposed to "Operate misfire free up to a minimum of 7,500 RPM." but at $50, is it worth the small advantage?

[TomoHawk]

I looked at the Pertronix D2070 Module mentioned here, and the description says "race only."  It sounds like it's for a 'performance' application, but isn't a L28 (or similar) engine the right thing to go with it? The description says, This is a race module that only draws 7.2 amps, a module that's optimized for the 6,000 to 8,500 rpm range.  I can understand the RPM spec, but I dunno what the 7.2 Amps means, with regard to the L28E engine. That's  86W from the ignition switch or relay.

 

[TomoHawk]

I finally got the GM module installed, and the engine runs smoothly, but the tachometer isn't responding.  I have a blue wire attached to the (-) pole  of the coil, and I understand that supplies  the spark signal to the ECU.  The wiring diagram also shows another wire (Blk/Wht) that goes to the (-) pole, bur I can't find that one anywhere in the area.

Has anyone else installed the HEI module and still have the tachometer working?