Re: Engine Kills
"GM HEI. . . .doesn't the ignition module just go out and the car won't start or is it sporadic"
NOPE, that is NOT accurate, actually, the HEI module is one tough, reliable ignition processor. They do not "just fail for no reason", NOTHING just fails for no reason.
Two areas I would look at, first, the main reason HEI modules fail, THE COIL IN THE CAP going bad, but that usually causes module death as the coil is going bad. To properly test the coil, emove it from the distributor, run it on an off vehicle electrical tester, let it get hot, up to operating temperature, that is where they have the most failure issues. Second, another failure area, the magnetic pickup to module two wire conector. These connectors hold both pickup wires into the HEI module. There have been more than a few wire end terminals in those conectors that were not crimped correctly, cuting a significant amount of the wire strands for both wires. As the pickup moves as the vacuum advance moves it, there is a change that after some miles, the remaining wire strands have disconected, but still butt up against each other, until the pickup is moved by the vacuum advance, then come back together when the advance goes back to rest. To test, use a hand held vacuum pump on the vacuum advance feed hose, with the engine running at idle, operate the vacuum advance. If the engine stays running, look elsewhere, if it stops, then easily restarts when vacuum is removed from the hose, look at the pickup wires inside the two wire connector at the HEI module.
There are many other reasons, but, these two are the most problem prone.