Weav's Vet

For a LT1

I've read about doing this but never have tried it. Any of you?

The reason I want to do it is that the threads for the bolts that hold the ICM on the heat sink are striped out. If I can space the coil off of the head with some washers I can get bolts with nuts of them and fix this mess. I guess what I need to know is will it hurt anything to do this?

Thoughts, opinions.......

Weav's Vet

Surely someone has heard of this..........

jaa1992

Been away from the computer for a few days.
Find several washers that fit on the stud that holds the power steering resevoir.
I used 6 total
Un bolt the power steering resevoir bracket
un bolt the ICM/Coil assembly
reinstall the ICM/Coil assembly using 3 washers between the assembly and the head on both bolts. It will give you about 1/4 inch air gap.

Weav's Vet

Thanks for the info jaa1992!

On another note I was able to drive the car just a little before it threw a PO1351 code because of the loose screws on the ICM. All I can say is WOW! The AFR's really woke this thing up, BIG TIME! Can't wait to get it to the dyno and track this weekend!

jmgtp

Like jaa1992 said, all it takes is a few washers. I did it when I had an issue with the motor skipping once hot. The ICM was getting heat soaked and failing. It worked and solved the skipping, though temporary. Eventually the ICM bit the bullet and I replaced. I don't see any downside to spacing it off the cylinderhead.

Weav's Vet

Got everything I need and this afternoon I'll put it back together. I went to Radio Shack and got some Heat Sink compound. If you go to the auto parts stores they'll give you dielectric grease which is not the correct thing to use. I read a lot about ICM's failing. Using the incorrect lube behind the ICM might be one reason why.

Black94LT1

I did not know that heat sink compound was different than dielectric grease. My car was missing at cruise in once hot, so I just regreased it over the weekend, it looks like I will be doing it again this weekend, good thing it is an easy job. The FSM only called it silicone grease.

MK 82

You are one of the few here who seems to understand that! But it is not lube. One of the causes of confusion is the use of improper terminology.

Dielectric grease is a non-conductive, silicone grease designed to seal out moisture and, therefore, prevent corrosion on electrical connectors. Being non-conductive, it does not enhance the flow of electrical current. This property makes it an ideal lubricant and sealant for the rubber portions of electrical connectors.

]

Thermal grease (also called thermal gel, thermal compound, thermal paste, heat paste, heat sink paste, heat transfer compound, or heat sink compound) is a fluid substance, originally with properties akin to grease, which increases the thermal conductivity of a thermal interface by compensating for the irregular surfaces of the components. In electronics, it is often used to aid a component's thermal dissipation via a heat sink.

Eddie

STL94LT1

I spaced my ICM with a few washers that last time I had the heads off, didn't notice a difference. Still running the original ICM, never used the heat sink grease, and it is still running strong (knock on wood).

Weav's Vet

Oops......I stand corrected

Weav's Vet

Here's what you need to get. It's about 12.00 an oz. but this little tube only cost 3.00 and change. It's size is .23 oz. Probably enough to do 4-5 ICM's.



The finished results

Al Borman

Nice work. I often wondered why GM did not use offset washers for the ICM heatsink, and decided to mount it directly to a HOT cylindar head....dumb...dumb...dumb. I did this "mod" on my '95. I need to get around and do it on my '94 .

Pete K

I wonder why they didn't space it, and slip a rubber washer in there to help with vibrations.

69427

High current, high duty cycle ignition modules create a lot of heat. Unless that heat can go somewhere, it will burn out the module. Your choices are putting a large finned heatsink on it (and blowing a lot of 200* radiator air across it), or you bolt it to a chunk of metal that will always be at a lower temperature than the peak temperature that the silicon part can survive at. Most newer silicon transistor parts are good for 250*-275*F. That 210*F head casting (with continuous internal coolant flow) is a walk in the park for that ignition transistor. Metal conducts heat quite well. Still or calm air doesn't.
Spacing the ICM away from the head looks good, but in worst case driving conditions the lengthened thermal transfer path isn't desirable.

69427

For the same reason that GM/Delco didn't put rubber washers under the HEI modules in their old distributors. These ignition modules' internal electronics aren't fragile printed circuit board construction, so they don't need the rubber washer bandaids.