Gm HEI upgrade on a 78 280Z

[sblake01]

All I see in the diagram is an HEI module that is connected to the coil and the ECU and grounded.

[zKars]

and that diagram is labelled wrong! The one labelled "ground wire from ECU" is a +12v connection, not ground!!!

[Zed Head]

The Zdriver wriiteup is designed to use the HEI module as a replacement for the "turbo ignitor" on the turbo ZXs with ECU dwell and timing control. The ECU triggers the "ignitor" or transistor in that case. The "signal" wire to the ECU and the ground wire takes the place of the two distributor wires. It doesn't apply to the NA cars that use the trigger signal from the reluctor in the distributor and an ignition module.

For a 1978 (and 74 - 77), you can connect everything in the engine bay, right at the coil and distributor. Just run jumper wires from the coil, one from coil + to B, one from coil - to C, and then disconnect the red and green wires from the distributor at the junction on the fenderwell, and connect red to W, and green to G. G and W read the pulse from the reluctor and B and C is the "breaker" circuit in the module.

The reason to disconnect the stock module is so that the HEI module can break the circuit. The HEI module will now control dwell, and making and breaking the coil primary circuit.

The main reason to do it is if your other module conks out, they're expensive, or if you want to try a higher power coil without the ballast resistor (which 1978 doesn't have any more anyway).

Edited February 8, 2012 by Zed Head
Fixed a couple of errors.

[TomoHawk]

Reading hat makes you wanna go out and put one in right now!

Do you have a favorite module to suggest? I read that some of the modules don't work so great above 5000 RPM. Maybe something from a 4 or 6 cylinder engine would work?

Edited February 8, 2012 by TomoHawk

[Captain Obvious]

I read that some of the modules don't work so great above 5000 RPM. Maybe something from a 4 or 6 cylinder engine would work?

I remember reading the same thing. I read it on the web so it was of questionable validity, but I do remember hearing that.

But on the other hand, I've had GM V-6's in the past that used their HEI modules. I had no ignition issues that I was aware of and I easily reached 6500 RPM.

Anyone have any thoughts on the matter?

[Zed Head]

In my reading around the web, I got the impression that there might have been some cars with the very early HEI systems that had some problems. But the cause might have been the coils, not the modules, since they both get very hot inside the distributor cap. Or just bad early modules.

Overall, it appears to an automotive urban myth. It gets repeated a lot but I haven't seen anyone confirm it.

I don't have a favorite module. It's a very common part, so market forces should drive the price down to low margin. You probably get what you pay for. I paid a few extra dollars for the BWD brand with a longer warranty.

If you try it, don't forget that the module is electrically grounded through one of the mounting lugs. Make sure that you have good contact or run a separate ground wire from the lug to a known good ground. Also, trim the little plastic nub off of the bottom of the module so that it has good thermal contact with the surface its mounted on. All ignition modules need to dissipate some heat when they're in use.

[TomoHawk]

I asked for a for your recommendation for a (favorite module) because if you go to the auto parts store, the guy behind the computer screen doesn't know what you mean by "GM HEI Module." They want a make, model & year, or they can't help you. I think ask for one for an 80s V6 car?

BTW- the 78 Buick Regal has a V6, and uses the module needed.

I do remember the tech-heads back in the 80s complaining about the module on the top of the distributor cap going bad because of heat.

Anyway, I drew up the wiring per Zed Head:

Edited February 8, 2012 by TomoHawk

[Zed Head]

Ask for an HEI module for a 1977 Camaro. They'll probably have a few different brands, like Standard, Elgin or BWD.

That diagram looks right.

One benefit of getting a module and connecting it now is that you'll know it works before the other one dies. If you wait until the other one dies, you'll be stuck not knowing for sure if it's the module or not. That's why I hooked mine up, then I left it for while, now I can't see any reason to disconnect it. I still have a stock module, disconnected, in its original spot. Good luck.

[TomoHawk]

Can you get some connectors for it too? Crimping on connectors will work, but something that looks like OE would be nice if the module is in view.

At Advance Auto:

1977 Chevrolet Camaro4.1L 250CI L6 Carb

BWD Ignition Control Module Part No. CBE4Z $24.69

Edited February 8, 2012 by TomoHawk

[Zed Head]

I never found any good connectors. I cut up a GM alternator plug to make my own but they didn't really work very well. I put the whole assembly in a metal project box which keeps the connectors from getting bumped loose and protects from the elements.

I think that there is a stock wiring sub-harness for the module, as its used in the distributor, that you might be able to find.

[SteveJ]

Can you get some connectors for it too? Crimping on connectors will work, but something that looks like OE would be nice if the module is in view.

At Advance Auto:

1977 Chevrolet Camaro4.1L 250CI L6 Carb

BWD Ignition Control Module Part No. CBE4Z $24.69

RockAuto has plenty of choices for the HEI modules, too.

[Captain Obvious]

it appears to an automotive urban myth. It gets repeated a lot but I haven't seen anyone confirm it.

Yeah, that's what I figured.

I do know from experience that the "inside the distributor cap" GM HEI modules were subject to heat related failures. You are supposed to use heat sink compound (thermally conductive goo) on the underside of those modules to help conduct the heat away from the module.

That, and there was a little breather filter screen in the bottom plate of the distributor that would corrode and clog. Once it was clogged, the temps went up.

I'm sure mounted on a fender wall, they would be fine.