When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My car runs perfect. No issues. I have a general question about the HEI system to you experts.
Back when I had my 91 with Tuned Port, I had multiple failures of my EGR solenoid - I suspect related to the location under the plenum and bolted to the T-Stat housing. This location collects extreme heat. The aftermarket solenoids kept failing. On a whim, I relocated the solenoid by routing the wiring and vacuum lines over the alternator bolt. Never lost another one.
Since heat seems to be the enemy of the Ignition Control Module shoved inside the HEI head, why can’t I just relocate the module outside the distributor on the firewall?
I have been studying the system and can find no reason the module must be inside. The Pick Up Coil and other parts seem to communicate with the ICM via wiring.
Please educate me because unless I am overlooking the obvious, I am about to experiment to see what happens.
Well, a small percentage of those "Modge" failures are due to improper installation. (besides junk units)
What I mean by that is, not applying the special paste under the modge.
Two things going here with the paste:
Its called Heat Sink Compound" (NOT dielectric grease)
And second, this product is not exactly easy to find.
As for your plan of attack, that will be a lot of wires that have to exit & return to the distributor body.
And, I would wager that the entire engine bay on a C3 is not too much cooler than the dizzy itself.
Good points, both of you. I agree most modules last a long time. I believe the older OEM modules were constructed to be more durable, as we see with many products.
However, would moving the module out of the distributor work?
Does the module have to be near the coil for any type of communication or magnetic influence?
At the least, after the work is done, it would be a simple 30-second task to change a module on-the-road if there were a failure.
I'm sort of doing what you want. My TI ignition module failed, so I replaced the TI module with an HEI module. My distributor generates a mag pulse, same as an HEI.
I mounted the HEI module to a heat sink and mounted it under the Master cylinder. It's been that way for a few years.
I carry a spare HEI module (mounted to a heatsink), so if I have a module failure, I can change the module in a few minutes.
Try not to over think the possibility of a "modge" failure. The original units were designed to last about 60,000 miles. The odds of failure are not worth fretting over and you can swap-out an old unit in a matter of minutes.
However.
Like others, I too, carry a spare modge already pasted, plus the tools to remove / install, in a Ziplock bag behind the seat.
You don't want to be that (worrywart) guy with the pickup truck with two spares in the bed. Just in case one spare goes flat.
Your biggest fear should not be whether or not a modge will fail or not.
Your biggest fear should be how to find a replacement on a Sunday night, in the cold / rain / darkness.
Pack a spare and a flashlight.
Enjoy. Drive it like its stolen.
Since you are using an ICM outside an HEI head, apparently they will work in an open environment.
Thanks for the info.
I also have a 3x3 section of finned heat sink from another project I had a while back. I had not thought of attaching the module to heat sink.
When I pull my intake for freshening this spring, I will relocate my ICM, attach it to the heat sink, and mount it in an accessible
place under my hood to see how that works.
The T.I. he refers to is likely the K66 known as the Factory Transistorized Ignition System. It does use a distributor with something like a hall effect sensor in it. The control box/"Module" would have been buried on the bottom front left fender.
The parts from the TI system are not interchangeable with many aftermarket parts. The module in my HEI has either 5 or 7 terminals on it. My K66 T.I. system was still functioning when I pulled the entire system and replaced all the parts with MSD Components. I had it rebuilt by Dave Fiedler and am using his newer control board for the K66 system. The system makes a good spark but I wanted a great spark.
One of the biggest problems people have is getting the new thermal paste in place before installing the module. If you use Too Much then it will cause trouble when the thermal paste melts out. Not enough and you can overheat the part.
Remove the HEI module from inside the distributor clean the mating surfaces with an alcohol prep pad before applying the least amount of thermal paste. I also clean the module base with the alcohol pad to ensure that nothing interferes with the heat transfer.
For you guys that want to carry a spare Ignition Module make sure it works. Bought a new module, installed, and engine still did not start. Bought another brand and engine started on the first try. My first replacement was dead in the box.
The original in there that failed on me was over 20 years old.
When trying the new one to see if it works, leave it in and keep the one you took out as the spare since you know it works. You dont know if the new spare you have does.
Nothing wrong with mounting it external on a heat sink. Easier to do a quick change for testing. I've always suspected that one thing that leads to early module failure despite them aging is stray sparks from a failing rotor. When the HEI rotor fails they seem to arm through to the area below the rotor. Signs of this are rust looking particles on the advance weights. Could your mod help with this or could the wires still be zapped if not shielded?
Also I think some of the Ford and Mopar guys have been using external HEI modules as a fix for their ignition issues.
Carrying a spare module is a good idea. While I've never had a bad module completely fail only making the engine run rough under a load.
Now when I when used to do long trips in the vette or old K5 blazer, I would carry a complete distributor as a backup. This for a module issue, but also in case the pickup coil under the advance weights would fail. The pickup coils I've had fail always cause a complete failure of the ignition ( no trigger).
Module Question
