[QUOTE=TopGunn;1578512690]What!!! Can't remember?? Getting old like me??????? I hear you.

Yes you guys are correct there are two different styles.

Here's a shot of the original cap that came in the car, I just took them both apart.....3 wire like yours and with that ground strap. Different for sure.........I think maybe I'll transplant that original that has the 3 wires and the strap into the new cap.
Tomorrow...gotta go to bed. Thanks for the help guys......Stay tuned

They changed to 3 wire in 75. The internal ground lead separates the grounding in the secondary coil from the primary coil.

 

Well, I put everything back together with the three wire coil and ground strap, only time will tell I guess. I'd be pleasently suprised if changing the coil back to the original design works but we'll see. In the mean time I'm keeping the spare in the glove box

Thanks very much to everyone for replying and all the suggestions.

Bill

 

If the old one does continue to work without fault, throw the one you removed in the trash.

 

A little post script to this..............

I accidentially ran across a thread in a Mopar forum regarding the same issue. The problem in his case was the poor ground caused by aluminium heads under an aluminium intake. I have the same setup. He solved it by running a #4 ground wire from the intake (I assume the bolt near the tach filter) to the frame and the problem instantly went away. He was also having some performance issues from the module not operating correctly so slightly different added problem but it's a thought. Pretty simple to run a ground wire so I think I'll do the same.

 

A couple comments:

The white module in one of the previous pictures appears to be an OEM part. Note the (blurry) 466 manufacturer code on the top cover. This indicates it was manufactured by Delco (the good stuff).

A malfunctioning alternator can cook an ignition module under the right conditions. The module won't overcurrent (it's limited to about 5.6 amps due to its internal circuitry) but the module will experience additional wattage due to the higher supply voltage if the regulator is defective. (Also, voltage spikes due to intermittent alternator output connections can damage the module.)

I don't see a module failure issue with a grounded TACH signal. A grounded TACH prevents any primary current from entering the module. No current means no power dissipation, and no damage. A grounded tach may burn out the coil, however, due to the coil having a continuous 12v across it. An intermittent TACH short is potentially damaging to the module as the short can cause high current in the coil, and then the module has to deal with the large flyback voltage when the short is removed.

I'll confess my lack of indepth knowledge of the HEI coil's mechanical construction. An ignition coil requires 4 connections (Battery and transistor/points in the primary circuit, and rotor/plug and GND/Battery lead in the secondary circuit). Did the different coil connections actually change electrically, or just in the manner in which way it was mechanically constructed?

 

Thanks for your comments and observations. I can't answer your HEI coil question but I suspect it's a modification mechanically that has the same electrical properties, but I don't know if it really does or not. If it doesn't maybe that's why these modules are failing. The coil came in the GM HEI dist. that came with the motor.

 

From my 1985 GM service manual (Pontiac) HEI Service Precautions " The tach terminal must NEVER be allowed to touch ground, as damage to the module and/or ignition coil can result".

Also "when disconnecting the leads from the module, observe color code on leads as they cannot be interchanged". It doesn't say what the consequences are. Don't know if it would even run.
Is it possible the connector is installed upside-down?