Coves4me

I'm doing a lot of work on my 94 right now and I took the ICM and coil off to clean it up and replace the coil. I also replaced the ICM while I was at it. My question is this.......The ICM mounts to an aluminum heat sink with fins and the bracket that mounts to the head of the engine. I've used the di-electric grease behind the ICM, behind the heat sink and behind the first of two plates that mount together on the head. Should I use grease against the head, also? Wouldn't it be smarter to use some washers as spacers to get some air behind the module for cooling? It makes no sense to me to mount this sensitive electronic device on the head of an engine. Or do I need to mount it flush for grounding? Any help is appreciated. Thanks in advance.

Mark

TWISTERUP

Mount it flush--the idea is to transfer heat from the ICM to the heat sink and away. FYI--- A new ICM would/should have come with a packet of thermal grease which helps conduct heat away from the ICM, dielectric grease which is used to aid conductivity.

STL94LT1

I used washers to space my ICM from the head.

captbob33

: I used the washers too! The intended design is to transfer heat from the ICM to the aluminum heat sink, not the engine head. The heat sink will then disipate the heat via it's cooling fins.
Dielectric grease is not the best heat transfer grease. I purchased a tube of Heat Sink Grease from Radio Shack, $2.99. It applies a silicone compound to help transfer heat away from electronic and electrical components. Follow the instructions on the package when applying the grease. Install the washers between the heat sink and the head, not the ICM and heat sink.

jmgtp

Before I installed the LTCC/LS1 coils I had done the same. It helped rid the car of a low RPM stumble that would only happen once the motor was hot and the ICM heatsoaked.

fuzzydawg

Aha! I've been trying to figure out why my 94 LT-1 stumbles in hot weather after getting off the highway and sitting in stop-and-go traffic. Is it pretty common for the ICM to get flaky when it's really hot? Any other electronics that suffer too?

I can't understand why I haven't seen other threads about heat problems with electronics. I'd have thought you guys down south (sorry, "y'all down south") would get this a lot.

ddahlgren

All electronics suffer from heat. Dielectric grease is not heat sink compound and do not interchange in any way. The IcM needs heat sink compound it is generally white and quite clingy hard to get off your hands. Dielectric grease goes on things like plug boots distributor cap connectors actually any connector a good candidate.
Dave

jmgtp

I should also state that my ICM was the original and when it failed I replaced with an aftermarket ICM. It wasnt long before I had ignition issues again. Spacing the ICM away from the head helped and alleviated the skipping but even that was short lived. I traced the problem back to poor quality aftermarket parts, specifically Autozone branded ICM and MSD coil. If you plan on replacing these two components I believe your best bet will be OEM parts.

At this point I was frustrated with my ignition and I decided to squash the problem. I purchased a set of LS1 coils and the LTCC brainbox. With this I ditch the factory ICM setup, gain coil per cylinder ignition performance and perhaps most importantly I removed the high voltage from the optispark. I haven't had an ignition problem since and my car is still using it's original invented opti.

I'm not saying the factory coil/ICM setup is bad by any means, when it works it works well. But when it comes time to replace these parts beware what you buy because there is a lot of cheaply made aftermarket parts that are inferior in quality.

Coves4me

I appreciate all of the advice everyone has submitted. I went to Radio Shack and purchased two small tubes of the proper heat sink grease and cleaned out the wrong grease I had used and re-applied the proper heat sink grease. I used two washers to space the mounting bracket about 1/8-inch away from the head. That should help some. Again, thanks for the advice. By the way, the ICM I purchased is a Borg-Warner that was over $100 at O'Reilly Auto Parts. Not cheap.

Thanks again.

Mark

littlesk8cracker

i purchased an ac/delco from zip-corvette when my stock icm went bad. it worked, but the car always had a check engine light until around 185-190 degrees. put another icm from advance auto parts on and check engine light went away and cars been great since then. i used the heat sink compound from radio shack

JM95

Several years ago with a heat problem in my OEM ICM I moved the mount off the head with 2, 1/2 inch thick Teflon spacers made from scrap. Added an 1/8 inch aluminum plate to the heat sink. Mounted this assembly with 2, 3/8-16 hex head bolts, reassembled the heat sink and ICM with Radio Shack Heat sink grease as well as heat sink to new aluminum plate (6061-T3 Alum) and reduced the operating temeperature by 70 fegrees F compared to head temp, measured with remote reading Pyrometer after hard driving shutdown. The 1/2 inch between the head and the new heat sink plate allows for significant laminar air flow up thru the gap. Have not had any heat problems since in hot Houston traffic. Good luck