[grivera]

Tested per our discussion: spark plug at dizzy cap-end of ignition wire, grounded out. Key in on position, touching dizzy ground-wire to - post on coil. No spark at plug.

[grivera]

Ended up being the ignition module-

Thanks for your help Luke!!

[PDC]

You up and runnin??? Great news!!!

[grivera]

Yes, sir!

Luke (Steelcityfirebird) spent some time on phone with me using process of elimination until it pointed at ign module. Dave’s Small Body HEI has module under dizzy housing. Pulled dizzy, swapped spare in and started up! Timed it and went for a ride - runs like a scalded ape!

[PDC]

Outstanding! Gotta remember - that’s what these forums are all about: sharing our collective frustrations to save each other headaches. Bet that motor never sounded as good as when you hit the key with the new module!

[steve25]

Likley a Heat related failure.

Good to hear it's running again!

I have seen folks make fairly big Aluminum clamp on heat sinks to the round shank of the Dizzy body to absorb Heat and dissipate before it gets up into the main body.

[TAQuest]

Yup, heat kills them.
Tip; Use thermal grease between the module and what it's mounted to.
This stuff; https://www.amazon.com/Super-Lube-98...995951197&th=1

[grivera]

Originally Posted by TAQuest

Yup, heat kills them.
Tip; Use thermal grease between the module and what it's mounted to.
This stuff; https://www.amazon.com/Super-Lube-98...995951197&th=1

Thank you for the link. I used the grease in the pill that came with my spare NOS module. Mine is attached to outside bottom of the dizzy housing - would like to add a heat-sink like below link but lack of real-estate under housing. Any other options?

https://www.amazon.com/ACDelco-10474...FYQ6ZQ204VD7HP

[72LuxuryLeMansLa.]

Originally Posted by grivera

Thank you for the link. I used the grease in the pill that came with my spare NOS module. Mine is attached to outside bottom of the dizzy housing - would like to add a heat-sink like below link but lack of real-estate under housing. Any other options?

https://www.amazon.com/ACDelco-10474...FYQ6ZQ204VD7HP

How many miles/years on that module? I could be wrong but it seems to me these things should be rated for much higher environmental temps than they experience under the hood......

[grivera]

Originally Posted by 72LuxuryLeMansLa.

How many miles/years on that module? I could be wrong but it seems to me these things should be rated for much higher environmental temps than they experience under the hood......

The failed module has about 2k miles- been on car since 2011 when I rebuilt the #s matching engine.

Dave (Dave’s Small Body HEI) recommends oil filled coil versus e-core types- says the oil type shed heat better. When I had the current engine built I was using the Summit e-core with the MSD dizzy and efi. I ended up reinstalling the DSB dizzy but didn’t reinstall the oil filled coil. Not sure if this contributed to the failure. Yesterday, I reinstalled it along with the new module.

https://www.davessmallbodyheis.com/s...il-filled-coil

Why Only An Oil Filled Coil?

This question comes up frequently. There are serious issues with epoxy filled coils.

Some of them are the heat rejection issue, oil transfers heat away from the heat source, epoxy rejects the created heat back into the source. An oil filled coil will feel hotter to the touch than an epoxy coil, because the heat is being transferred to the jacket with the oil, but held at the source with the epoxy.

“If we look at the failures ofr HEI modules "for no apparent reason" in the coil in cal large HEI's, we find that soon after the coil begins to go bad from heat failure layer shorting issues, the HEI module gets over worked to failure. In fact, it is possible that as the epoxy coil is failing, it will dispatch numerous modules before an unsuspectng tech finally reaizes the coil is the source of the failures, and replaces the coil, hopefully, with an oil filled coil.

With my small-body HEI's I have designed them to use an easily obtained over the counter oil filled round coil, no problem.

With any ignition system, testing of components is critical, doing it the right way is essential. To test all coils, remove them from the vehicle, find a good auto parts store with an off vehicle electrical tester, run the coil on the machine, and let it get to operating temperature. Resistance tests are no longer adequate to find an issue with a coil that has failures occuring only when a coil gets to operating temperatures. “

[72LuxuryLeMansLa.]

Originally Posted by grivera

The failed module has about 2k miles- been on car since 2011 when I rebuilt the #s matching engine.

Dave (Dave’s Small Body HEI) recommends oil filled coil versus e-core types- says the oil type shed heat better. When I had the current engine built I was using the Summit e-core with the MSD dizzy and efi. I ended up reinstalling the DSB dizzy but didn’t reinstall the oil filled coil. Not sure if this contributed to the failure. Yesterday, I reinstalled it along with the new module.

https://www.davessmallbodyheis.com/s...il-filled-coil

Why Only An Oil Filled Coil?

This question comes up frequently. There are serious issues with epoxy filled coils.

Some of them are the heat rejection issue, oil transfers heat away from the heat source, epoxy rejects the created heat back into the source. An oil filled coil will feel hotter to the touch than an epoxy coil, because the heat is being transferred to the jacket with the oil, but held at the source with the epoxy.

“If we look at the failures ofr HEI modules "for no apparent reason" in the coil in cal large HEI's, we find that soon after the coil begins to go bad from heat failure layer shorting issues, the HEI module gets over worked to failure. In fact, it is possible that as the epoxy coil is failing, it will dispatch numerous modules before an unsuspectng tech finally reaizes the coil is the source of the failures, and replaces the coil, hopefully, with an oil filled coil.

With my small-body HEI's I have designed them to use an easily obtained over the counter oil filled round coil, no problem.

With any ignition system, testing of components is critical, doing it the right way is essential. To test all coils, remove them from the vehicle, find a good auto parts store with an off vehicle electrical tester, run the coil on the machine, and let it get to operating temperature. Resistance tests are no longer adequate to find an issue with a coil that has failures occuring only when a coil gets to operating temperatures. “

That's more in line with my thinking....Rather than ambient temps I'd be looking for an electrical cause. It's possibly just a defective part....It's not like quality control is a priority in manufacturing for most corps these days.

[TAQuest]

Originally Posted by 72LuxuryLeMansLa.

That's more in line with my thinking....Rather than ambient temps I'd be looking for an electrical cause. It's possibly just a defective part....It's not like quality control is a priority in manufacturing for most corps these days.

These go out usually due to heat. If you put one on without the grease it will not last long. Well known fact among us old school guys.

[72LuxuryLeMansLa.]

Originally Posted by TAQuest

These go out usually due to heat. If you put one on without the grease it will not last long. Well known fact among us old school guys.

It's also a well known fact amongst Electronic Technicians that most of the heat is internal! This is why you must use "Heat Sink Compound" to help thermal transfer from the module to the heat sink, in this case the body of the distributor!

[grivera]

Originally Posted by 72LuxuryLeMansLa.

It's also a well known fact amongst Electronic Technicians that most of the heat is internal! This is why you must use "Heat Sink Compound" to help thermal transfer from the module to the heat sink, in this case the body of the distributor!

My replacement had a capsule with thick, white grease which I used - should I assume this is a heat sink compound?

[TAQuest]

Originally Posted by 72LuxuryLeMansLa.

It's also a well known fact amongst Electronic Technicians that most of the heat is internal! This is why you must use "Heat Sink Compound" to help thermal transfer from the module to the heat sink, in this case the body of the distributor!

Well Karl, you have to put it all together. Could be a lot of things. We have some clues to work with. Since you are a using your credentials as an Electronic Technician then you know all about what heat does to electronics.
Your first clue was the first sentence;

"I went for a long drive on Sunday in 90 degree weather"

Most likely it was heat since that IS what kills these most of the time. If it was cool out and it died then I would be on board with your quality control theory.
If you diagnose the cause wrong then you will be fixing it again.

[TAQuest]

Originally Posted by grivera

My replacement had a capsule with thick, white grease which I used - should I assume this is a heat sink compound?

Yes, that's the stuff. Was there any on the mounting surface of the bad one?

[grivera]

Originally Posted by TAQuest

Yes, that's the stuff. Was there any on the mounting surface of the bad one?

There was a clear greasy substance between housing and old module.

[steve25]

Clear silicone grease and white heat sink compound are two very different things!
Also you only want a film of white heat sink compound as any more use only hurts the heat transfers properties.

[STEELCITYFIREBIRD]

Originally Posted by grivera

Ended up being the ignition module-

Thanks for your help Luke!!

....Anytime Will

[STEELCITYFIREBIRD]

Originally Posted by steve25

Clear silicone grease and white heat sink compound are two very different things!
Also you only want a film of white heat sink compound as any more use only hurts the heat transfers properties.

Never would believe too much would hurt heat transfer, excess will just squeeze out.
Same deal with seating a processor in a computer to the heat sink.
Messy likely, but not enough will leave void/s between the two mating surfaces, and that IS the purpose of the HSCompound.