From Dave Ray (IgnitionMan), he reads this, and other sites, and then, asks me to post responses for him, when he feels he might be of help.
"Please post this on the Team Camaro board, for hotrodf1.
HEI modules more so than not, ARE NOT usually the cause of HEI coil failures, just the opposite, coils fail modules. HEI in cap coils are epoxy filled, and do not leach heat created in their cores outward, they hold the heat in the center of the coil, and fail. The overheating causes the windings insulation to fail (called layer shorting), and when the wiring touches together inside the coil, the resistance and load gets exponentially greater, overloading the coil, and most times, module to failure.
There are a number of areas to look if coil failure, and subsequent module failure continues. System voltage, test at full operating temperature, 2,500 rpms, ad the distributor BATT terminal. 14.40 to 14.60 volts is fine, lower won't hurt, unless it gets down around 10 volts or so, and then, the HEI will just fail to work, Too high, coils will overheat and fail. HEI coils have a grounding bar under them, goes from the coil yoke to the center terminal of the 3 wire connector, and to distributor ground. Dirty, increased resistance, failure, or, no contact, coil won't fire. Older rotors were made form lower quality plastics and can transmit spark through them, increasing resistance and heat, failure. The carbon brush under the coil is also a place problems can start. The order it is installed is, cap, brush with spring, insulator donut, coil. Some put the carbon brush in after the insulator, placing the brush off and upwards of the rotor bar, making for serious increased resistance, heat, and coil/module failure.
Testing the HEI coil used to be OK with only an ohm meter, but not today. Load testing the coil off the distributor, on a machine designed to do so, IS the right, and only way to test them. If the module is bad, then I would seriously think the coil(s) were responsible for the module going out.
Whenever I do a large cap HEI, I ALWAYS remove the coil in cap coil, and install a remote, round oil filled coil, just saves a lot of problems from that heating device on the top of the distributor jokingly referred to as a coil. This removes a lot of under cap temperature, and usually, stops the coil/module failures in their tracks.
I just saw a situation I have never seen before in an HEI module, it would drive the scope in my distributor machine fine, made excellent pattern, but wouldn't drive the coil to make a spark. I have not seen that happen before, partially failed module."
Dave, and I, hope this helps fix the problem.
Regards,
Milton