Is this stuff ok to use on ICM

[tayto]

i remember reading some computer nerd thing where they would apply it with a rubber roller or a credit card. thin thin thin. i usually put a thin coat on with my finger

 

[454cid]

We had a member awhile back that seemed to have issues with the CPU dielectric compound he bought. When he switched to the packet included to the ICM the problem disappeared. I'd probably give the fancy stuff a try, just to see, if I had it.

 

[Road Trip]

I have used Arctic silver. Works fine. Can't monitor temps like my computer but it works fine there also.

i've been using artic silver for 14ish years on ICMs. I seem to recall the guys on thirdgen.org using it

Thinking back when I converted my 93 Camaro back to a 93 GM ICM (undoing more PO f00k3ry) it came with a compound.

Electronics and automatic transmissions have one thing in common: The harder they are worked, the more
self-destructive heat is created. And the better that the excess heat is somehow siphoned away, the longer that they
will work reliably. And I think that the variable reliability of the ICM is a perfect example of this. I've been
on the hunt for detailed schematics for the ICM, but so far the best I've been able to come up with is this
simplified block diagram:

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As you can see there's some key signal conditioning going on. An especially important
signal is the conversion of the sine wave coming off of the distributor pick-up coil
into a square wave, where one destination is to be sent to the ECM as the all-important master
"Reference" signal. (No Reference Signal = no sparks + no fuel injector pulses + no fuel pump
relay control coil drive after 2 seconds.)

But the really heavy lifting is done by the "Amp" that grounds / ungrounds the primary winding
of the Ignition Coil. (Which in turn generates/collapses the electromagnetic field around the
coil secondary windings, providing the sparks that ignite the mixtures in the cylinders. (As well as
Schurkey's preferred HEI test setup that allows us to verify the presence of these blue-white beauties.)

It takes AMPS at a lowly 12V in order to provide the necessary high KV kick in the secondary windings.
So I have no doubt that the circuitry driving the coil primary gets plenty hot...even before the
ambient underhood heat is considered. (Especially in a TX summer day engine bay with the AC on while pulling a trailer.)

Given all this, in order for the coil driver circuit to not run as hot as an old light bulb filament,
we need to maximize the heat conduction away from this module. A good thermal compound will
do just that. I think of this as a Cheat to Win moment -- improving something simple that is better
than what these machines came off of the assembly line with.

Curious as to what the state of the art is, I ended up where the geeks go for this kind of info (Tomshardware.com)
and grabbed a screen shot of the top handful of the 90 different thermal compounds tested:

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If there's any overclockers in the audience you will see some of your favorites listed. For those not comfortable
with using cutting-edge boutique stuff, I put an arrow next to the industry standard tested. (Dow Corning TC-5625)

And for those wondering about the electrical and thermal conductivity of the Dow Corning paste, here's a spec sheet
that you can reference: (Dow Corning TC-5625 performance specs)

****

By the way, thermal compound has a useful working lifespan and should be renewed periodically.
(Especially if whatever is between the ICM and it's mount was troweled on back when Clinton was
president.) Speaking of which, thermal compound is like bondo -- the thinnest possible layer is
preferable. You don't want to preclude actual metal to metal contact between the peaks of both
mating surfaces. Instead you just want to fill in the microscopic valleys in-between the peaks so that
they *also* conduct the heat. (Best case, you can practice your thermal chops on an older computer's
CPU/heat sink interface, for nearly all modern CPUs have built-in thermistors on the die and report
their temps.)

EDIT: Over in the corvetteforum I found an interesting discussion on this topic for those that
just can't get enough of this stuff: ("ICM heat sink compound")

****

If anyone is still reading this, hope you enjoyed the electronics thermal rabbit-hole that we just
took the briefest peek into. And yes, I've added this preventive maintenance item on my list of
things to do before I make the chore truck tow all my tools & test equipment over to NH so that
I can share them with my grandkids. Don't want my ICM to overheat & put me on the side of the
road with all my (obsolete) treasure out back. :0)

Safe travels this Memorial Day weekend.

Cheers --

 

[Schurkey]

I have no doubt that the circuitry driving the coil primary gets plenty hot...even before the
ambient heat is considered. (Especially in a TX summer day engine bay with the AC on while pulling a trailer.)

Ambient temperature is less important than underhood temp--although higher ambient can and generally does lead to higher under-hood temp.

By the way, thermal compound has a useful working lifespan and should be renewed periodically.
(Especially if whatever is between the ICM and it's mount was troweled on back when Clinton was
president.)

GMT400 vehicles were an "early 1988" product, they made a heap of them in '87. My service manual set has a copyright date of 1986.

So...and I understand that this kinda dates me...we're not talking about Clinton, we're potentially talking about Reagan.

 

[Road Trip]

Ambient temperature is less important than underhood temp--although higher ambient can and generally does lead to higher under-hood temp.

Yeah -- while writing that I was wondering what kind of heat stacks up in @L31MaxExpress's doghouse when
he's putting a proper fully-loaded flogging on?

It must be similar to the underhood heat that we were fighting on that old '75 Chevy Monza that we swapped a sharp
355ci engine into. You would open the hood and the heat wave would just punch you in the face. I remember being
impressed that the old large-cap HEI ignition never faltered in the back of that oven of an engine bay. :0)

 

[L31MaxExpress]

Yeah -- while writing that I was wondering what kind of heat stacks up in @L31MaxExpress's doghouse when
he's putting a proper fully-loaded flogging on?

It must have been like the heat wave whenever we opened the hood on that old '75 Chevy Monza that
we swapped in a sharp 355ci engine into. You would open the hood and the heat wave would just punch you in the face.
I remember being impressed that the old large-cap HEI ignition never faltered in the back of that oven of an engine bay. :0)

I can tell you my IATs will hit 180F on a 115F day and that is with the air intake near just behind the hood. The old 350 got hot enough it was cooking LS D585 coil packs, which is part of the reason the 383 has a distributor again. When I swap it to the 58x system, my coils will be on the frame rails in front of the engine, using LT1 style plug wire routing.

 

[L31MaxExpress]

Actually it was even hotter than that last summer at one point. The engine compartment is definitely cooking.

I can also say that with an open element air cleaner the 1987 G20 was hitting 140F IATs in 40F ambients temps and that was with the iron manifolds on it.

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[L31MaxExpress]

I will also add, that evening is the night I plumbed the oil cooler back up on the 383. After adding the cooler back into place, 10-15 psi more oil pressure at hot idle. 35-40 psi hot idle pressure with the cooler and 25 psi without it.

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[GoToGuy]

I was not happy or comfortable with my 86 K3500 always running over 200°F , this was brand new. And opening the hood was sticking your head in a 400 ° oven blast wave.
So after about 90 days of open and jump back , it was nope no more. Drained everything, axles, trans, transfer case, oil, filter, fuel filters, radiator. Installed a 180 ° thermostat. What difference. Open the hood no longer get a 2nd degree flash burn. Way cooler. Last year for carburetor and leaded fuel. So no issue with electronics and water temp.

 

[L31MaxExpress]

I was not happy or comfortable with my 86 K3500 always running over 200°F , this was brand new. And opening the hood was sticking your head in a 400 ° oven blast wave.
So after about 90 days of open and jump back , it was nope no more. Drained everything, axles, trans, transfer case, oil, filter, fuel filters, radiator. Installed a 180 ° thermostat. What difference. Open the hood no longer get a 2nd degree flash burn. Way cooler. Last year for carburetor and leaded fuel. So no issue with electronics and water temp.

That same van would run 3/4 up the temp gauge when it was less than a year old. Dad complained multiple times to the GM dealer it was bought from and it had an 11 bladed fan and larger fan clutch on it when it was next picked up.