[azbirds]

My HEI coil has burned up twice in the last year. The new one was an Accel that lasted less than a year. I have a hidden switch to energize it coming off the battery. Is this too much voltage? What else could be killing coils?

[Geoff]

No, not too much voltage. What do you mean by 'burned up'?

More info please.

[azbirds]

It just stopped working. I thought it might be the module that was causing the no spark condition. Battery voltage to the coil was good but no spark. I was at a friend's house and he had a coil to throw at it, so I did, and it fired right up.

[Geoff]

Áre you aware that with HEI, battery voltage must be checked with the engine running? Just checking with ign on, but engine off, is unreliable.

[azbirds]

Yeah, it's getting 13.9 volts.

[HWYSTR455]

Some modules have a thermal protection built in, and will stop working when the coil overheats. If you wait a while, and it starts, then it's a bad module would be my guess.

As the module and/or coil go bad, the interval the thermal protection engages gets closer and closer together.

By removing the coil, it can cool, and allow it to work again.

Some aftermarket HEIs suggest that the coil specs must match the module, but I haven't heard of any issues with mix and match.

Some coils are just junk, and some poor manufacturing, they fail early. If you're running an ignition box, such as a MSD 6, coils tend to fry faster too. Even if you run the low resistance bushing as required. (should run one regardless)

I suggest replacing the module harness, have seen those having internal opens, and many of the aftermarket HEIs have cheap ones to begin with. They are inexpensive.

Next time it cuts out, wait like 5 min, and pour a bottle of water right on the cap where the coil is. Place your hand on the coil and make sure it's cool, and see if it starts. If so, try replacing the module, but at that point, it probably needs a coil too.

You can place your hand on the coil at the point it dies, if it's super hot, you have this dreaded issue.

When I had this issue, I went back and forth, replacing modules and coils, until I finally replaced both at the same time. It's frustrating. (and expensive)

Technically, in cap coils are not efficient, and you should divorce it from the cap. But the parts to do so are not so cost effective. These are the main reasons I don't use HEIs, and I still don't understand why folks are so fixed on using them.

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[HWYSTR455]

Hm, maybe I didn't figure it out, looks like I went to a different dizzy the last time I had this issue:

http://forums.maxperformanceinc.com/...light=HEI+Coil

Here's another topic on pickup/coil matching:

http://forums.maxperformanceinc.com/...d.php?t=408761

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[Geoff]

People use HEIs because they are such a good ign system. H-E, High - Energy, as the name suggests. At 5000 rpm, HEI cranks out about 60mA. Points, 5mA.
I know which one I would rather have.

HEI was almost too reliable, never failing & so no maintenance done. Spark plugs eroded & grew & this is what caused a lot of problems.

When you consider the huge number of cars that came with HEI, the failure rate was extremely low. The only failure I have seen with HEI was a coil fail in a brand name unit, nearly $300 from Summit; Chinese units that I regularly use here are well made & work fine.

The most important part of the coil as far as ign performance is concerned is the material the coil laminations are made of: the purity of the metal & the percentage & type of materials alloyed with the base metal. Never talked about...

I treat my HEI like American Express: never leave home without it...

[george kujanski]

I'm with Geoff....my HEI equipped cars never failed, no coil failure, no button failure. Had a pickup coil fail once due to wires moving back and forth. Hard to understand why some coils and buttons fail with regularity. Doesn't make sense, and I doubt if it's a design issue. Too many millions of HEI's successfully on the road.

It would be interesting to measure the temp of a hot coil......the wire should be rated to at least 100*C I would think. Since the coil is a passive device, temps high enuf to damage the wire coating and/or vibration would be the only failure mechanisms I would suspect.

George

[HWYSTR455]

In my case, when it stopped running, you couldn't place your hand on the top of the cap/coil, that's how hot it was.

Odd thing is, it ran fine for a while, but only appeared on a long trip (300 miles). Short trips it was fine.

All you have to do is google 'HEI problems' and you will see it's not as fool proof a system as all say it is.

If you look at some of the threads here, there is different pickups and modules, so it is possible to get a mismatch, or something along those lines.

You can't ignore the fact that myself, and the original poster of this thread have had issues. And there are more.

I'm not knocking HEIs, but they aren't as good as people think. I know many have had success with them, and that's why I at one time used one, but after my experiences, no more. And there's still the whole advance curve/weight/springs thing.

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[azbirds]

Update. It did it again. I pulled the cap and the module was pistol hot. I left the cap off to cool it down and it started right up. So it probably wasn't my coil, just the sitting time last go around. It has the white goop under it to insulate. Is there something else I can use as a better insulator?

[HWYSTR455]

Technically, it's not an insulator, it's a thermal paste, which helps transfer heat to the dizzy body as a heat sink. But. I suggest changing all at once, the pickup, module, and coil. One will take out the other and you can chase your tail replacing stuff.

If it's doing it because you replaced the module, or if it does it again, try swapping the pickup wires around.

.

[azbirds]

Here's one more bit of info. I can drive around all day and it's fine, or shut it off and start it back up no problem. If I let is sit for 15-20 minuts it will not start. I did try pouring water on it when it wouldn't start, and after that it fired right up.

[Geoff]

Az,
To answer your question: yes there is something better than the white heat transfer paste. There is now a silver paste with silver in it; silver is a veeeeery good conductor of both heat & electricity. Electronic stores should have it.

[HWYSTR455]

Originally Posted by azbirds

Here's one more bit of info. I can drive around all day and it's fine, or shut it off and start it back up no problem. If I let is sit for 15-20 minuts it will not start. I did try pouring water on it when it wouldn't start, and after that it fired right up.

After what it fired back up? Waiting a longer period of time?

It still sounds like an overheat thing, the module as I said sometimes has built in heat protection. Once it cools off, it will start.

Same with the coil, if the coil gets too hot, it slowly starts misfiring, which gets worse and worse, and then finally won't run. That's what I was thinking, it might be the coil. I was saying to pour water on the top of the cap where the coil is, see if that helped. But if you're saying the module is too hot to touch then it may not be the same symptoms I experienced.

But, one way or another, it's a failing part, be it the module, pickup, or coil. That's why I was saying just replace them all at once, and avoid having to figure out which it is. Oh, and replace the short wiring harness too, those go bad as well.

.

[azbirds]

It has to sit a long time to cool off enough to start. The car runs great for with no deterioration in performance. I drove it on the freeway for about 18 miles and shut it off. It wouldn't start 30 minutes later. I took the cap off one time to cool the module, and poured water on the cap another. Both times the car started immediately after.

[HWYSTR455]

Yup. And it's clear now, thanks.

Yeah, fully rebuild or replace it, is my recommendation. If you go one item/part at a time, you will be pulling hair out in short order.

Summit has a 'kit' that isn't priced badly, and all you would need in addition is the pickup:

https://www.summitracing.com/parts/sum-850030/overview/

Swap your weights and springs over and you should be good. (if you replace the whole distributor)

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[george kujanski]

Just thinking here.........I think if the voltage to the HEI is lower than expected, say 13 volts or lower, instead of 14 or so, the module may try to compensate with a longer duty cycle at street speeds, (meaning higher average current values thru the coil and module). Since the electrical power dissipated is a square function , i.e. P = I*2 x R, that would cause higher temps in the module and coil.

That could certainly be an issue (lower voltage to the HEI) if the coil resistance wire is not bypassed when doing a conversion to HEI. Can't think of any other reason why the module and/or coil would run excessively hot. Certainly use good heat transfer goop under the module. The silver-based stuff is what is used to mount processore to a heat sink in computers. Look for the stuff online wherever computer parts are sold.

George

[HWYSTR455]

Originally Posted by azbirds

My HEI coil has burned up twice in the last year. The new one was an Accel that lasted less than a year. I have a hidden switch to energize it coming off the battery. Is this too much voltage? What else could be killing coils?

Yeah, I don't think that's the issue George, but think it's a solid 12v if not more.

.

[azbirds]

I've got a hidden power switch from the battery to the hidden switch straight to the distributor. I did put the silver goop under the module, but haven't had time to run it around and heat soak it yet.