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Discussion Starter · #1 · (Edited)
I've now spent hours looking for a definitive answer to the question regarding which grease/compound is to be used on the bottom of the ignition module when removing/replacing or just checking/servicing.

The best answer I've found is the following, from a MotorTrend article (see below). But holy smokes the debate out there is crazy. That said, when I checked my '94 (100,000 mi, original owner) ignition module a few years back after the computer threw some codes, I pulled the ignition module and there was nothing on the bottom (although on second thought, I vaguely recall there might have been some residue, so maybe it just dried up).

I applied dielectric grease -- and it's been smooth sailing ever since. I absolutely get the concept of why heat sink compound (like Artic Silver) would be superior at heat transfer, but that material does dry out (especially given underhood temps/engine temps/operating environment) -- hence, dielectric being the correct choice (per article pic below). Interestingly enough, absolutely nothing mentioned about this in regard to the procedure for replacing the module or any reference to grease/compound to be used in the three orginal GM shop manuals I have for this '94 truck .

Final Thoughts
Also, when researching this topic I noticed that many (if not most) people seemed to be using WAY TOO MUCH grease/compound. Keep in mind, we are talking about mating two almost perfectly flat metal surfaces. In order to have maximum heat transfer from the module to the heat sink, you need as much metal to metal contact as possible. You could make an argument that using no grease might even be the most effective solution if corrosion wasn't a potential issue (probably why I found none or little when I inspected my unit -- the factory probably used very little if any grease that overtime disappeared from engine heating cycles).
The idea behind using the grease is two fold - first, it reduces or eliminates the chance of corrosion of the metal surfaces, and second, it is there to fill and bridge the micro cavities that may exist on the metal surfaces*. Hence, only the slightest amount of product is needed -- the thinest film possible, really. If you slather on a ton of product, you are actually creating an insulative barrier and wrecking any chance for proper heat transfer -- and thereby going to cause component overheating and premature failure.


Finger Font Engineering Eyelash Circle



GM HEI Ignition - Popular Hot Rodding Magazine

Also, here's a pic of a Delco Remy replacement ignition module...note the packet of clear (not white) "silicone grease."

Font Gas Rectangle Motor vehicle Concrete


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* Snip below is from an article discussing thermal paste in PC builds, but it shows a useful illustration regarding surface imperfactions.

Font Line Slope Parallel Diagram



How to Apply Thermal Paste - Intel
 
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