Re: Distributor ?'s
Just info on what happens to the in cap HEI coils. They are epoxy filled, and epoxy is not a heat leaching compound, it is a heat rejection one. As we all know, coils produce heat internally, starting at the inner core, center of the windings. the center is where the most windings heat remains, and must be drawn away from, and out of the core, to the outer surfaces of the windings.
Since epoxy holds heat, the windings retain more resistance than they should, and overheating results. Eventually, the epoxy compromises, and cracks on its outer surfaces, and coil heat literally causes the insulation layers between the windings to disintegrate, allowing windings to touch, changing the heat production possibilities, and circuit resistances, over loading the coils to failure. This is called "layer shorting".
An added issue is usually that along the way of over heating, windings touching, and failure, the loading from coil to module increases, and causes module failure long before the coil finally gives up. Add to all this that the in cap coils have a coil cover, so even less cooling air flow travels across the coil, making things even worse.
Epoxy is usually used to make carb spacers that reflect manifold heat back into the manifold, away from the carb, reject heat away from something.
Oil as a cooling media in coils works very close to what an old car had, with a liquid cooling system and no water pump, called "Thermo-Siphon". The heat production media heats up the oil in contact with it, the oil rises to the top of its pool, and outward in a canister, to the inside of the outer jacket, begins to fall down the pool wall, cooling as it flows, then at the bottom of the pool, is drawn back into the heat source, to cool all over again, thermo siphon.
I've taken coil covers off a lot of wrecking yard HEI's, still in their cars, and found more than I'd like to see of cracks in the in cap HEI coils. Those coils finally got so hot, they cracked their epoxy bodies, and failed. The key give away is to look at the car, no accidents, no dents, the coil is cracked, and the car was junked because it stopped in its tracks for its very last time, owner done with it, wrecking yard.
That is why I always suggest one of the MSD, or before, Mallory large HEI coil change over caps, which allow for a remote coil, mounted off the cap. I go with a round oil filled coil then, coil, and usually, HEI module failures stop.
Just info to consider.