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Old 01-01-2020, 06:41 PM   #1
toolboxchev
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HEI Ionizing Issue

So I have read about this in the past. About every 3,000 to 5,000 miles I will have to pull my HEI cap and clean it out due to some type of corrosion buildup on the brass tabs for the plugs. Also some build up on the rotor yet minimal.

I read somewhere that it is Ionizing Air in the cap that causes this. I will run rough upon cold start up until fully warm. Slowly causes a loss of mileage and power.

I have to scrap, sand it off and spray out the cap with carb clean and re-assemble.

Is there a way to prevent this from happening? Remember hearing about some drilling a hole in the cap yet this will let ambient moisture in most likely causing more issues.

Would love to hear the cause and or any mods that can be done to prevent this from occurring.
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Old 01-01-2020, 09:08 PM   #2
lutronjim
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Re: HEI Ionizing Issue

Is there a chance you have an incorrect rotor causing a large arc? I ran one for years without any problems
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Old 01-01-2020, 09:47 PM   #3
toolboxchev
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Re: HEI Ionizing Issue

Well I hope not, the rotor always comes with the cap. These are the MSD units.

Found this on Crankshaft Coalition:

Plug gap

Don't be tempted to excessively widen the gap. The correct gap is 0.035"- 0.040" for the majority of cases. Using plug gaps wider than that is unnecessary when using a basically stock HEI ignition. Wider plug gaps (or faulty ignition wires) cause voltage spikes in order for a spark to occur. This in turn causes the cap to fill with ionized air, and this can cause erosion/degradation to the components along with spark scatter and/or voltage bypassing to the distributor advance mechanism, shaft, etc. It is hard on the secondary ignition components in general and just isn't needed in the vast majority of cases.

The large diameter of the cap helps to prevent this and it works well enough in a passenger car, even with the wider gaps that were used for some applications. But once the RPM goes up and the cylinder pressure increases, the chance of a misfire increases dramatically with a wider plug gap.

My plug gap has always been .045. No misfires attributed to Carb or Distributor, Timing.

I know GM tried numerous plug styles with gaps as large as .060 so the above is just the opinion of the writer which is not bad advise.

Last edited by toolboxchev; 01-01-2020 at 09:55 PM.
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Old 01-11-2020, 02:52 AM   #4
dmjlambert
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Re: HEI Ionizing Issue

So, are you going to clean it up and try plug gaps of 0.035"- 0.040" and see if the problem goes away? It will be interesting to hear back from you if that fixes it.
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Old 01-11-2020, 08:34 PM   #5
toolboxchev
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Re: HEI Ionizing Issue

Yea that is what the plan is, as soon as it stops raining. Fighting another issue right at the moment and waiting for some parts from MSD. Those techs are a wealth of knowledge.

I did clean it up and its running, did not re gap the plugs, yet. I am a lazy turd sometimes!

Found out also, no matter the coil nor module I would need a 6AL box to get anything to reliably jump a gap bigger than .040. That would be coming from the MSD techs.
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Old 01-11-2020, 08:45 PM   #6
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Re: HEI Ionizing Issue

Are you interested in a gap bigger than .040?
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Old 01-13-2020, 01:08 AM   #7
toolboxchev
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Re: HEI Ionizing Issue

Yes I was, this has been going on for a long time. Was using Accel Super Coil with Accel module. Supposed to get more voltage to the plug to jump that gap.

Apparently this is not true. It just makes the spark more difficult to jump that gap. Well at least that is what they are teaching me in theory.
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Old 01-13-2020, 10:23 AM   #8
vince1
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Re: HEI Ionizing Issue

I don't like spending extra money on vehicles when I don't have to and have always considered these fancy ignition components in that category. Original HEI is good enough for me and I will put up with replacing an occasional module or pick up coil. Granted, I no longer like playing with points and would look for alternatives to that system.

If you are talking computer controlled and rev limited distributors, that stuff is way over my head.

It does seem that one or more of your components is not matched correctly to get the job done that it has to do.

Last edited by vince1; 01-13-2020 at 10:31 AM.
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Old 01-13-2020, 12:21 PM   #9
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Re: HEI Ionizing Issue

80's Dodge 2.2/2.5 engines used a vented distributor cap.

https://www.rockauto.com/en/moreinfo...=2242&jsn=2242

If your wondering about the contacts on the cap, the plug wires push through.
https://www.rockauto.com/en/moreinfo...89266&jsn=2264
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Old 01-13-2020, 12:42 PM   #10
toolboxchev
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Re: HEI Ionizing Issue

Right now, am not looking to vent, MSD techs say yea sure drill a hole in it, but then you have another problem.

Would be great to find a cap with brass terminals and factory vent.

Interesting thought on those plug wires.
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Old 01-13-2020, 12:48 PM   #11
toolboxchev
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Re: HEI Ionizing Issue

Right now, am not looking to vent, MSD techs say yea sure drill a hole in it, but then you have another problem.

Would be great to find a cap with brass terminals and factory vent.

Interesting thought on those plug wires.
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Old 01-14-2020, 11:46 PM   #12
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Re: HEI Ionizing Issue

Why not just set the gap at .035 and put a new distributor cap on there and see if it solves the problem? Is there an actual advantage to wider gap?
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Old 01-15-2020, 03:11 AM   #13
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Re: HEI Ionizing Issue

Quote:
Originally Posted by dmjlambert View Post
Why not just set the gap at .035 and put a new distributor cap on there and see if it solves the problem? Is there an actual advantage to wider gap?
There must be if the engineers at GM specified .045 for every carburetor fueled 350 ci truck engine from 1976-1989. Maybe it was an advantage in the smog system? I set mine to .044 and it runs great (cheap Chinese HEI).
OP didn't say what he was running though. -BA
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Old 01-15-2020, 12:35 PM   #14
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Re: HEI Ionizing Issue

I just read somewhere and can,t remember where but they said to go to .40 gap to fix this
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