I've been having some starting issues, and while I trouble shoot the actual problem in another thread, I figure it's time to replace some of the older parts and wiring. Gonna replace the ICM, distiributor, coil, and some of the wiring and connectors.

While trouble shooting, I picked up a new, parts store OE distributor. Turned out not to be the problem, but I figured it's IN the car, and the old one was....well OLD! Was gonna pick up a GM ICM, and replace the old coil too, but is that distributor OK or is it worth the $100 extra bucks to step up to a performance distributor? Easy enough to return, but I've traditionally NOT had problems with the actual OE style distributors over the years. Was gonna keep it.

 

The OEM distributor should not be a problem if it is installed correctly. If it is positioned so that the rotor proximity is reasonably close to the appropriate plug terminal at maximum advance (highest spark energy demand) you should be all set. This may take a bit of measuring and positioning.

Voltage stress is not much of an issue on HEI style distributors, either, so long as an original design rotor and original design cap are used. Some of the aftermarkets have done away with the deeply grooved arc quenching barriers, and make reliability questionable.

The rest of the unit is low-level signal switching if you are using a separate coil and trigger, and only using the internal HEI switching module as a trigger. However, if you are still using the HEI module to switch the coil primary, a generic Chinesium HEI module of unknown fidelity becomes a questionable entity. Also, a generic replacement Chinesium pickup coil of unknown inductance can erode a lot of confidence.

 

The knock against the OEM doesn't appear to be in it's construction. As an example, a used HEI, provided it's not some exceptionally high mileage part, is more than capable from a mechanical point of view. It's the electrical components that come in to question. So from that, you can say the parts store replacement is up top the task (and not the worst of offshore junk), once you address what's in it.
For the record, what distributor did you get? Conventional HEI? Small cap? External coil?

 

Yes, small cap, external/Moroso coil. Haven't purchased the ICM yet.

 

So, for what it's worth, I've never come across anything that proved/implied or other stated that the basic distributor is flawed mechanically. Provided it's not worn out, it seems the OEM product is good to go with whatever you can throw at it.

As for the ICM, while I've eliminated mine from the ignition and can't relate any direct experience, I understand that there are several aftermarket upgrades that are more or less on an equal footing. MSD appeared at one time to be a leader. Accel and Nology also ranked very well.

 

I dont see any issues with them. As said if the rotor cap and icm is in good shape they work well. Had no issues at 600-800 hp boosted/nitrous combos so far

 

You guys are generally saying what I've experienced. No real issue with the distributor mechanically. As for the ICM, I've had good ones fail, and crappy ones last for years. Who knows.

I'm currnently running the Holley EFI, and they have a dual sync plug and play unit that offers the ability to run sequential and coil on plug ignition. Not that I need it, but it does eliminate the ICM. Awfully expensive though at just under $500!!!!!

 

When I purchased my new ICM I went with the Jegs brand and it has been working now for 3 years. The cost was relatively the same as a stock replacement but the Jegs was good for 8-9000 RPM. I believe the one I replaced was 5500. Not sure if this is just a marketing tool but I have run my rpm's up and get no ignition cut out.

 

It has been my experience that whether it's an inexpensive no brand ICM , or an expensive one with brand name pedigree , the common factor in long service life is the thermal compound used , and how clean the distributor's ICM mounting surface is when the new ICM is installed .

If you do not go to an electronics supply store and buy the good thermal paste the computer builders use and instead use the little bit of useless pus that comes with a new ICM , that ICM will NOT live the nice long life it otherwise would have had the good heat sink grease been used .

Likewise for not cleaning the distributor's ICM mounting surface down to nice shiny metal before the new ICM is installed , and this too is regardless of whose name is on the box the new ICM came in . I use 90% rubbing alcohol and a rag to remove ALL traces of the old , turned to crud thermal paste whenever installing a new ICM and in over 50 years of working with the GM HEI ignition I've not had ONE repeat ICM failure simply by following the above listed process .

PS , you will note my use of the different terms ;

"Thermal compound" "Thermal paste" , and "heat sink grease"

This is deliberate , because I've seen it sold under those 3 names . The brand I use is called "Artic Silver" but any high quality thermal paste will do . Just remember too , that "dielectric grease" is NOT thermal compound , even though I've seen little tubes of what looks a Hell of a lot like dielectric grease and not thermal compound , come in the box with the new ICM .

Happy Motoring ......

 

X2 clean and good thermal paste. I think i also used artic silver is what i used but cant recall

 

I still had the stock ICM on my truck, 170k miles later. If it were to die due to heat and leave me stranded like apparently it does everyone else, i would just relocate it somewhere not attached to the engine lol