Hi, Guys,

Been a Loooong time since I last posted.

This time it is a simple question: does the ICM find its ground return through its base? If it does, then conductive thermal paste should be used. If it does not then either type should work. <YIKES! that IS the answer: just always use conductive and it should

always work!>

Please let me know if my logic is in error! I shan't be offended!

TIA

Larry

Yes use the conductive paste. sleek

I didn't even know there was a choice. I suspect it's a moot point. Seems to me that the ICM mounting screws would take care of any grounding concerns.

The ICM grounds through the screws and the metal rings surrounding the screw holes.

these distributors are known for corrosion and that is why the conductive paste is used

It's a good question. I had not thought about that. I used to use a non-conductive thermal paste there (Thermalloy Thermalcote).

With the metallic-particle paste, I guess you must take extra caution to avoid getting any near electrical contacts to avoid making short-circuits.

Without conductive paste, somewhere near the screw (perhaps the thread flanks themselves), there will probably be enough pressure to punch through whatever paste you apply, making electrical continuity.

Electrical current can flow through the screws, as well as directly from the metal baseplate to the distributor. The current distribution through each path depends on the relative resistances of each path, with current mostly taking the path of least resistance.

[This message has been edited by pmbrunelle (edited 05-29-2023).]

quote Originally posted by olejoedad: The ICM grounds through the screws and the metal rings surrounding the screw holes.

Often only 1 hole and screw and not just GM units... If screw isn't bare metal and clean then iffy ground there can kill ICM and ECM.

quote Originally posted by sleek fiero: these distributors are known for corrosion and that is why the conductive paste is used

While known for "rust" problems, conductive pastes are NOT used. Worse many conductive pastes known as Liquid Metal "Eat" Aluminum and not only in areas it touches.

Any White HS Grease and others will work to transfer heat better then Dielectric Grease many ICM come with.
Many get leftover Gray HS grease from Dell etc that works w/o Silicone Oil that White and some others have.

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The Ogre's Fiero Cave

As an electronics enthusiast, generally conductive silicone thermal compounds conduct heat BETTER then non-conductive carbon-based thermal pastes.

The latter are ‘safer’ if electrical conductivity is a concern, but don’t transfer heat as well as silicone compounds.

As the bottom of the ICM is ‘ground’ as well as the distributor base, so a conductive thermal compound will be better than a non-conductive paste.
VN

quote Originally posted by Vintage-Nut: As an electronics enthusiast, generally conductive silicone thermal compounds conduct heat BETTER then non-conductive carbon-based thermal pastes. The latter are ‘safer’ if electrical conductivity is a concern, but don’t transfer heat as well as silicone compounds. As the bottom of the ICM is ‘ground’ as well as the distributor base, so a conductive thermal compound will be better than a non-conductive paste. VN

"As an electronics enthusiast" .... Funny... in the sad way. Silicone oil/grease are Not electrical conductive and most HS compound base on it are Not conductive same as White HS Grease that's mostly Zinc Oxide. Others use different Oils as carriers instead of Si because Si doesn't play well w/ some other parts so like often can't use on direct contact w/ many actual chips/dies.

No, the base is Not a Ground to GM HEI or DIS.
Hemmings like Haynes and others have a lot of BS in their books and web sites. Even in your "Example" shows 2 different stories.
Pic is using Standard Brand Dielectric grease because For Decades was used by nearly everyone and many ICM still come with it. Current Text say heat transfer not dielectric "grease" but tries claim "use under ignition modules" that is funny and not in good ways. Ω shown is for another part not the ICM.

GM installs most ICM types Completely Dry without Any Lube or HS compound for Decades.
And often the problem that kill them are other things like people that doesn't clean the 1 screw that is the Ground for HEI modules.
Modules have 2 "grounds" and 1 Screw for HEI, Large Black Wire for DIS, is the Main Power Ground.

GM Did putout a TSB because some where installed w/ Black Oxide coated Screws that causes problems because the coating cause a poor Power ground.

Other "Ground" shown in Nearly All Doc's is Not a Power Ground but "Signal Ground" wire for ECM/PCM control of Timing.
If the main ground has problems then ICM can try to use the other causing many problems even killing the ICM ECM/PCM or both.
See cave, ground myth under HEI in menu.

[This message has been edited by theogre (edited 05-31-2023).]

quote by theogre "As an electronics enthusiast" .... Funny... in the sad way.

I just won't get into a pissing contest with you and I’ve been using Dow Corning 340 Heat Sink Compound for decades. It is a white thermally conductive compound to improve heat transfer from transistors to the heat sink or chassis.

quote by theogre No, the base is Not a Ground to GM HEI or DIS

Obviously, the metal plate on the ICM doesn’t need an insulator, so Conductive or Non-Conductive thermal compound will work.

I recently rebuilt my distributor, and the new GM ICM came with a tiny packet of white thermal compound to "transfer heat away from the module".

As a note, my original ICM had 137k miles on the clock, NEVER failed, and it had ‘clear grease' between the ICM and the distributor.
VN

I use a silicone conductive grease that has fine copper powder in it. It offers both thermal and electrical conduction.

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