I thought I would through this out there. Doing a search came up with a lot of unanswered question on the subject. My 85 seems to be frying ignition modules in the distributor. The upgrades are only a year old. Holley coil, accel cap & rotor, MSD spark plug wires, did have an holley module and did have a accel module. Have another accel module on the way. The vette will run with a new module installed but not for long. Question is has anyone had a module problem like this? I would like to correct it but so far can't find anything to correct other than a new module. Can't afford to keep replacing modules, so any help on the subject would be helpful before I have it towed to a mechanic. Thx..

 

I am going to assume that the problem started when you installed the Holley coil????? Can you reinstall the factory coil to see if your problem goes away????

 

Is there a valid reason why you are subjecting yourself to this sort of self-made pain? Put a stock Delco module and coil in it and spend your time and money on stuff that will actually make the car go faster. I'm running the stock module and coil in my turbo 355, and it works just fine.

 

It sounds like a faulty coil and/or a mismatched combo.

I suggest you gather up the part numbers and contact Holly to see if they can shed some light on the problem.

 

The upgrade was a year ago when I started autocrossing. It was running fine till now. I tried to put the stock coil back on but the coil wire was arcing back to the coil housing. There are burned marks on the coil housing now. But when I put back the holley coil, it is fine. Go figure. Stock module back in now but I will not run it due to the fear of burning it up. But it will fire up the vette.

 

I was not trying to make the car go faster with these upgrades. Now, making it burn more Efficiently with a stronger spark was what I was after. That was just my preference.

 

Hope your putting the dielectric grease on the bottom of the module before installing it. It will not last long without it.

Ken

 

Yes, dielectric grease was used.

 

So, you want us to believe that you were after better fuel mileage???

Larry
code5coupe

 

No, just burn more.

 

DO NOT put dielectric grease on the bottom of the spark module !!!!!!!!!!!
You should put heat sink grease on the bottom of the spark module. Dielectric grease is clear, heat sink grease is white and meant to conduct heat out of the spark module!!!!!!!! Dielectric grease does not conduct heat as well and should not be used.

There isn't a thing wrong with the GM HEI ignition system, it was designed to last a long time and to provide a hot spark. You can increase spark energy with a different coil by increasing the primary inductance which then will limit the rpm because spark energy will fall off into the operating rpm range. Or, you can increase the primary current which will shorten the life of the spark module. GM has designed the HEI for a good compromise in spark energy, energy holdup at high rpm and long spark module life. When you buy an aftermarket coil, how do you know what compromises were made? I recommend you go back to the stock spark coil.

 

possibility that ''ripple'' is killing your ign modules...an alternator may appear to be putting out like it should but due to internal probs, throwing in high voltage voltage ''spikes'' that fry the ign modules quickly and can also smoke your ecm, radio, gauges, scanner, etc....many parts stores will check your alternator for free, ask that they check ripple also, just an extra flip of the switch

 

jfb: Thank you! I have been trying to get out this sort of information to the forum for years, and explaining things until I'm blue in the face, but I swear few people actually listen. I appreciate your help and knowledgeable explanations. Again, thank you.
Mike

 

For the 1986 it's important to get the colors of the ignition coil wires and pick-up coil wires right. I suspect it's the same for the 85. Not all ignition coils are compatible with all pick-up coils. It's a wire color issue that has to be right.

Accel sells two coils for the 86, each with different color wires. You need to match the coil wire colors with the colors of the wires on the pick-up coil.

That could very well be your problem. The ignition coil and the pick-up coil are not compatible.

In the 1986 Corvette FSM one page lists which ignition coils can be used with which pick-up coils, determined by wire color. I've posted the exact quote from the FSM before (probably not available on the Forum now since it's been so long ago), but if you really need that info I can track it down and re-post it here.

When I researching this issue a few years back, I called Accel and MSD (maybe another one but I can't recall which) and asked about this. Best I came up with was it was a polarity issue. I recall Accel said for their coils, you've got to get the wire colors right; ignition won't fail right away but will down the road.

MSD, on the other hand, said their coils will work with any pick-up coil wire color.

I never talked to Holley about their coils, but my advice would be to give them a call and see what pick-up coil wire colors their ignition coil requires.

Since you have a new Accel module coming, be sure you get the wire colors right or you may end up frying the new module too.

Hope this helps.

Jake

 

Thx Jake. That is very good information to put out there and your right on the money. The holley coil also has the different color wires. My application required the red & white wires. I believe I have narrow down the problem. I'm kicking myself in the a-hole because one of the first thing I said to myself was not to forget to reinstall the ground clip in the new distributor. Well, I forgot. Sh#t happens. Check the ohms on the coils, ohms not within spec. There both done. Well, now just waiting for the new parts and I'll be back on the road. I want to thx you members with your suggestions. It did help me perform a more thorough check of the situation. Your suggestions gave the Inspiration to keep looking.