I was blundering around the net and stumbled accross an F-body webboard. They were discussing the ICM that is mounted on the LT1/LT4 front of the passenger side cylinder head via a heat sink that is bolted to the head and the ICM is bolted to the heatsink.

A guy did a free mod intended to let the ICM operate cooler. He simply put some nuts between the heatsink and the head to act as spacers so the heatsink is not fully in contact with the head. The theory was that the heatsink may pick up excess heat from the head and this would minimize heat gain from the head.

This assumes, of course, that the ICM normal operating temp is LESS than the temp of the head. If that is the case, then the mod would seem to make sense.

But, if the ICM's normal op temp is HIGHER than the temp of the head, then this mod would effectively interfere with the ICM's heat being transferred to the cooler surface of the cylinder head.

I have heard that ICM's get H O T, the question is do they normally operate at a temp higher than that of the surface of the cylinder head to which they are mounted?

I'm thinking not, simply because I have faith in the expertise of the GM engineers that designed the existing setup. I'm thinking they intentionally mounted it to the head because the ICM runs hotter than the head and therefore the idea is for the ICM's heat to transfer to the head and be dealt with by the engine cooling system.

Discuss...

 

The ignition control module pulses the primary of the spark coil and its power transistor is operated as a switch, so it doesn't dissipate a lot of power and doesn't make much heat. I would expect that the head operates at a higher temperature than the ICM on its heat sink in air, but I am going to defer my opinion to the GM engineers. On my L98, the ICM, called a spark control module is inside the distributor and the distributor gets heat from the block, about the same condition as putting it on the head. If it were me, and not knowing the reasons for putting the ICM on the head, I would opt for a cooler place, like the inner fender!

 

There are two theories here.

One the head is making the ICM hot and you pull it away from the head to reduce the heat transfer to the ICM

Two the ICM runs so hot that the head actually pulls heat away from it. However, if you can get air into the space that has a lower temp than the head I think it would also help.

My take on it is that cooling off the ICM will not gain you any greater performance in terms of HP. It may lengthen the lifespan of the ICM, but I believe it was designed to run at under hood temps so why mess with it.

A small word of warning, that heatsink is also connected to part of the coil. This part of the coil may need to be grounded so whatever changes you make, keep the thing grounded to the head.