Since my wires have been burned out and the firewall chared beyond recognition can anyone tell me where the 3 wires plug into for a new HEI ignition system. I am working on a 1978 GMC Royale, motorhome, and cannot locate any electrical block or connection. The only thing I am sure of is the wire from the ignition switch. Am a newbee.

 

HEi generally only requires one wire, the one from the ignition switch (usually pink).

We may need pictures.

- Eric

 

OK, there were 3 wires to the distributor that were fried and some kind of plastic part that melted away. The new ones show 3 wires leaving so there isn't some kind of control module they plug into? Originally the ignition system used HEI but someone converted it so they could use an Acell super coil. What a bastardized piece of work! I am not sure how to install a new HEI system now. The fire burned the vacuum lines to the power brakes and something else behind the firewall. As well as the cruise control diaphragm, water hoses, speedometer cable and throtle cable. Wish I I could Blame it on a defective alternator but fair is fair.

 

What is an ignition module?

 

It's the electronic control circuitry for the HEI; it is located inside the distributor underneath the rotor.

http://rmcavoy.freeshell.org/diagrams/HEI.jpg



Is that the wiring harness on the distributor as shown on the left upper side of the image above? Or are you referring to a wiring harness coming from somewhere in the engine compartment?
This site has some good info on the HEI and its wiring: http://www.crankshaftcoalition.com/w...EI_distributor


Actually, the remote coil is a very good modification to the HEI: it replaces the in-cap epoxy coil with a remote oil-filled coil. Getting rid of the epoxy coil above the electronic module removes a lot of heat from the under-cap area, so the module runs cooler and as we all know, cooler electronics perform better. The oil-filled coil also runs cooler than the epoxy coil, so it doesn't run the same risk of insulation breakdown as the epoxy coil and it should last longer and perform better.

 

Yes there are three wires on the distributor that must plug in somewhere. On my RV the end where those wires attached is a piece of plastic melted over the wire, which is where it went to. Because it is so fried I can't tell what it is.

 

From the photo posted above, you can see that the three wires come from the distributor base and plug into the cap. These are the wires that control the coil in the cap. There is a single pink wire from the firewall harness that plugs into the BATT terminal on the cap. If you have a tach, that wire plugs into the TACH terminal on the cap. That's all there is to the HEI wiring.

 

There are 2 connectors on a GM HEI, the outside 2 female connector is the Batt+ (switched power) the other female spade is for a tach hookup. The inside connector goes from the cap to the module. Red wire to B terminal on the module, green wire to the C terminal, and the black is ground. See attached:

 

OK, thanks! So all the wires were fried at the distributor do I need a new distributor or just a new modules?

 

Sounds like you need a new cap, rotor, wires, pickup, and module.

That being said, it would probably be cheaper to buy a complete replacement HEI distributor.
In your case (late-'70's GMC motorhome), an aftermarket unit would probably not adversely affect your performance (the way it might on a higher-compression, earlier engine).

- Eric

 

Thanks

 

Hey my Royale is purring like a kitten. Now does anyone know where I can get a new cruise control diaphragm?

 

Fantastic!

As for your question: I have no idea.

- Eric

 

My HEI distrubutor is a Delco-Remy, not sure of the year, the pink wire that goes to the Bat side of the HEI does not appear to be in my harness.



Is the yellow wire previously used with a non HEI distributor from the coil to the starter solenoid eliminated ? The harness I am using had two wires one yellow one black running to the positive side of the coil. I'm guessing that the black is my power supply and it should run to Bat on the HEI in place of the pink power wire.

Which side of the starter solenoid does the purple wire attach R or S ?
I have read conflicting advise on this.

BTW the car is a 69 Cutlass with a 69 455.

 

Well, since your car didn't come with HEI originally, it won't be there...

The purple wire comes from the neutral safety switch and goes to the S terminal on the solenoid. The yellow wire runs from the R terminal on the solenoid to the coil. This provides a full 13.8V to the points for starting. It is only hot when the key is in the START position. The black with orange stripe wire that also goes to the coil is the resistor wire that knocks the voltage down to about 9V so the points will live longer. This wire is only hot with the key in the RUN position.

Your HEI needs a full 13.8V in both the START and RUN positions. The easiest way to do this is to 1) replace the black/orange resistor wire with a regular copper wire and 2) connect BOTH the yellow wire and this replacement for the black/orange wire to the BATT terminal of the HEI cap.

Now your HEI gets 13.8V in START from the yellow wire and in RUN from the replaced black/orange wire.

And for those who are wondering, the reason why newer cars only need one wire to the HEI is because the ignition switch on those cars is designed so that one wire gets power in both the START and RUN positions.

 

The purple wire goes to the S terminal. Your car may or may not need the yellow resistance bypass wire depending on whether your coil wire has power in both the run and on positions of the ignition switch.

 

Joe,

So when i am done I will still have a yellow wire to the solenoid R side and the purple wire to the S side.

On the HEI I will now have three wires to the Bat side.

Where does the replacement copper wire originate and what guage do you suggest ?

Thanks

 

Yes

No, two wires, the yellow one from the R terminal on the solenoid and the new copper wire that replaces the resistor wire from the firewall connector.

It comes from the firewall connector under the brake master cylinder. Ideally you would separate that connector, remove the terminal with the resistor wire, and install a new copper wire and terminal. That's a lot of work and really isn't necessary. You can simply cut the resistor wire close to the firewall connector and splice the new wire to it. I always use solder and shrink sleeving on splices like this. Use the same gauge wire as the yellow wire from the R terminal.

 

OK, thanks Joe and Eric for the responses