Can you blow an HEI module?

78Delta88

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May 23, 2022
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Yep, I got into Mopars in High School, learned to keep spare good distributor in the trunk.
 
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g0thiac

G-Body Guru
Sep 6, 2020
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How about an HEI that grenaded shards of metal?

As I said before, I do not have good luck when it comes to engines, so hopefully this proves it 🤔😭😭😭

This came off the 305 of my Pontiac, not sure if this happened when the engine finally went driving down the highway in Madoc, or just from over time but when I took the cap off to use to run on the other one?

Well there wasn't much underneath, and theres rust all over too.
 

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Wageslave

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Jan 25, 2017
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The one for the 301 should be the same. Just stay away from the $15 units, they are pretty much crap.

HEI is fairly simple, once the reluctor produces the signal the module then triggers the coil and produces spark in its simple form.

Similar to Ford's system except Ford has the module mounted on the fender and then triggers the coil. GM's HEI is all self contained in the distributor, which makes it very convenient. I have a GM style HEI unit for Ford 302 but haven't tested yet. It's a basic unit I picked up from Falcon Global.

I few years back I put the Ford electronic setup on a 65 Mustang that originally came with a point system and it really woke up the engine response on the 289 2BBL. The unit I used came off of a 78 Granada with a 302/auto.

The main Achilles heel of the HEI is the pick up coil. The two small wires break over time and then you have a "crank-no-start" condition. In the interim as the wires wear out, which is prior to breaking, is when you get all the goofy stuff that's hard to diagnose. Even the ohms test can come back ok, yet the pickup coil is on its way to being junk.
Fun fact, a lot of people would put one of those 4 pin modules onto a heat sink and wire it to the Ford distributor to get rid of the Duraspark box. The Duraspark has about the same reputation as an Optispark for reliability.

Another fun fact, if you have a car that is hard to crank over or is prone to pinging, you can use a 5 pin HEI module and have a switchable 10 degrees of timing retard.

When I was working with my Megasquirt box, I learned a LOT about these little modules.
 
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Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
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Galaxy far far away
The one for the 301 should be the same. Just stay away from the $15 units, they are pretty much crap.

HEI is fairly simple, once the reluctor produces the signal the module then triggers the coil and produces spark in its simple form.

Similar to Ford's system except Ford has the module mounted on the fender and then triggers the coil. GM's HEI is all self contained in the distributor, which makes it very convenient. I have a GM style HEI unit for Ford 302 but haven't tested yet. It's a basic unit I picked up from Falcon Global.

I few years back I put the Ford electronic setup on a 65 Mustang that originally came with a point system and it really woke up the engine response on the 289 2BBL. The unit I used came off of a 78 Granada with a 302/auto.

The main Achilles heel of the HEI is the pick up coil. The two small wires break over time and then you have a "crank-no-start" condition. In the interim as the wires wear out, which is prior to breaking, is when you get all the goofy stuff that's hard to diagnose. Even the ohms test can come back ok, yet the pickup coil is on its way to being junk.

In electrical work, ohms tests are only half the story. People often fail to also perform voltage drop tests.

The self contained packaging of coil in cap HEIs does cause some issues and limitations. There are good reasons why other manufacturers used remote mount modules and coils instead. Even Chevy switched back to remote coils in 87. HEI modules live in a very harsh environment for them under the cap.
 
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Ugly1

Royal Smart Person
Oct 26, 2021
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How about an HEI that grenaded shards of metal?

As I said before, I do not have good luck when it comes to engines, so hopefully this proves it 🤔😭😭😭

This came off the 305 of my Pontiac, not sure if this happened when the engine finally went driving down the highway in Madoc, or just from over time but when I took the cap off to use to run on the other one?

Well there wasn't much underneath, and theres rust all over too.
Helped a buddy build a V8 S10 day after it was on the road he smoked a mustang racing. Shortly afterwards the truck would barely run. When checking it out the rotor bushing was gone. No spring, no button, just gone.
 
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69hurstolds

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Jan 2, 2006
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For stock, I've never had an issue with a coil in cap. ACDelco on the coil, or nothing on those for me, however. Same with many of the electronic components. I don't buy all that aftermarket stuff, so I'm a poor source for reference on that. I can say that if you go with Standard parts, or Borg Warner on the sensors/ignition parts, many times they're as good as the GM stuff as they made many of the components over the years for GM anyway. I'd shy away from Bosch, however. I've had nothing but bad luck.

ANYWAY...here's my guess on this on where to look- all for free. Just a little time.

Check the wire leads on the main coil and the terminal on the pickup coil in the distributor. It SOUNDS as if one or both may be of the "Chevy" variety, i.e., reverse polarity than what the Pontiac would use. This can cause ALL SORTS of issues, especially poor running if you can even get it to run. You want the "clear" (acutally just translucent) connector for your Pontiac V8. It's the GM Yellow or GM black connector you don't want. Keep in mind some aftermarket parts use black connectors if they don't have clear, so be careful with that.

Also, the wires for your in-cap coil should be of the red/white variety. The other one is yellow/red. You don't want the yellow/red one. You need either GM p/n 1876209, 1985474, or 12498336.

Pickup coil GM p/n 1876495 or Standard LX304 or equivalent. GM pickup coils usually have fatter wires. Which is always better. But the other versions likely work ok.

Here's one from Canada on ebay. 20 bucks.


1684325042371.png

1684324181940.png



Here's a Delco coil for $45 plus tax. Can't really see them, but this is the red/white wire version coil.


1684325275683.png


If you just HAVE to have the original part number coil, here's one:



Also, I have this in my files. It's from a Pontiac forum somewhere, don't recall where, but it has some info on the pickups.
1684323126215.png
 
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cloudhome

Not-quite-so-new-guy
Jul 6, 2020
15
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Glenview Illinois
I purchased a couple of those $40 Accel distributors sold on ebay back in 2020 as packaging defects. Brand new billet distributors with module from Accel. Had one in my 84 SS and it worked fine until I put a MSD High energy coil in the cap. 5 miles from home and the module let go, resulting in a $166 tow bill. Took the module out of the 2nd one.....that one crapped out about 2 miles from home. Bought a NAPA 4-pin module and that's been working fine. Replaced it with a MSD heavy duty module, and keep the NAPA in the tool kit as a spare. Distributors we're a good deal, but throw the module away.
 
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Bonnewagon

Lost in the Labyrinth
Supporting Member
Sep 18, 2009
10,564
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Queens, NY
you can use a 5 pin HEI module and have a switchable 10 degrees of timing retard.
Now THAT is an incredible tidbit to know about. Could make starting up much easier.Thanks!!!
some info on the pickups.
Wowsers I never knew any of that. Now I have to go see what I have been using all these years. I am pretty sure if not OEM Delco then Standard which used to be my go-to brand. I once stripped a Turbo TA and I figured the coil was a bit better and I have been using it ever since.
 
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