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I've had issues with my ignition system, mostly revolving around the ICM, since 2015, documented on here, the longest stretch typically being about a year between failures. I've done it all in terms of diagnostics and parts replacement, testing, etc.
The only thing I haven't done is rip the whole distributor out and replace it all at once, i.e. the nuclear option (in my opinion). I've seen several others with similar issues to mine who have done this and never posted again, which leads me to assume their car stopped eating ICM's.
I thought I had a good fix recently with my heat sink added under the distributor plate, but alas, it has failed again (at about a year, again).
I have tested everything and found no obvious issues, ran all the wiring, etc. etc. etc. I'm going to check the alternator for voltage spikes, again, but don't expect to find anything. I have a new dizzy on order, with a lifetime warranty, just gonna pop it in, check the timing, and see if whatever issue was eating ICM's before will go away.
My thinking is that there just has to be something, probably small, unnoticeable, issue with the current distributor that is causing failures over time. Literally every part has been replaced at one time or another.
At least with the warranty if I have a failure I can get my money back, haha.
Starting this new thread since I know there are folks out there who are also in the same situation (or will be). If you don't see me posting back it's because all went well.
Hi RedLeader289, I just replaced yet another ICM myself, and TBH my "nuclear option" plan would be to relocate the ICM out of the distributor and into it own mounting area, with a CPU heatsink and fan scavenged from an old PC. If I ever do get around to it I'll be sure to create a thread with lots of pics
Any rate, I've been running Pertronix for a while now and no issues. Large cap HEI. I also use thermal compound under it, similar to what vorteciroc showed a few posts earlier.
Any rate, I've been running Pertronix for a while now and no issues. Large cap HEI. I also use thermal compound under it, similar to what vorteciroc showed a few posts earlier.
that’s why I think it’s something minuscule in the dizzy itself, cuz I’ve tried everything else.
that’s why I think it’s something minuscule in the dizzy itself, cuz I’ve tried everything else.
One thing I also did was to add a small braided ground strap to the housing and tie it back to my main ground point at the back of the cylinder head. I don't really trust the distributor clamp to provide a solid ground for the housing, which then goes back through the manifold, bolts with sealer on them, etc...
One thing I also did was to add a small braided ground strap to the housing and tie it back to my main ground point at the back of the cylinder head. I don't really trust the distributor clamp to provide a solid ground for the housing, which then goes back through the manifold, bolts with sealer on them, etc...
Where on the housing did you tie to? Since I’m going to have it out I figure I might as well do this too haha
On the bottom of the distributor housing, I drilled a small hole in a spot that won't interfere with any internal components. Then used a self tapping screw to attach the ground strap with a ring lug.
It was a small generic braided strap I got from the local auto parts store. Then ran that strap to a ground stud on the back of the cylinder head where all my other grounds are co-located.
I didn't think there were any good Brands for the ICMs/ HEI Modules...
I gave up on them years ago, but if you guys found something reliable, please post it.
Thanks!
Many years ago when I started my Business, I only offered component rebuilding (Distributors, Carbs, TBI Units, Fuel-Pumps, Oil-Pumps, Alternators, Starter-Motors, Etc)...
I used to offer the Pertronix Module for Points Distributor rebuilds.
Half of them would just die without warning 12-Months later... Others lasted for years and years.
I used to offer the Pertronix Module for Points Distributor rebuilds.
Half of them would just die without warning 12-Months later... Others lasted for years and years.
The Pertronix in my brothers 914 is the current suspect in several drivability issues.
All of this makes me edgy when contemplating getting a programmable distributor so as to lose the weights, springs and vacuum can features I presently have.
I've an old and ancient MSD small cap distributor and a 6AL box. It all works very well but is tedious beyond belief to tune.
No HEI for me though but that's just a personal preference.
All of this makes me edgy when contemplating getting a programmable distributor so as to lose the weights, springs and vacuum can features I presently have.
I've an old and ancient MSD small cap distributor and a 6AL box. It all works very well but is tedious beyond belief to tune.
No HEI for me though but that's just a personal preference.
What do you do for a timing curve?
I just used a timing light and set it to GM specs for my crate engine. Nothing fancy
I just used a timing light and set it to GM specs for my crate engine. Nothing fancy
Fair enough.
While (I'll assume) you might have to get into the springs to make the curve correct for what GM asked for, I found one of the limitations of the HEI was the lack of being able to reduce the amount of centrifugal advance that's available.
It doesn't appear to apply to your application (which is great to have a drop-in distributor ready to go), but for me, all of the advance is front loaded (18-20° initial) and the centrifugal adds another 14° or so for the total. IIRC, an HEI has better than 19° baked in and no reasonable means to reduce that. Reasonable meaning not having to weld up the advance slot and work from there.
Once you're satisfied with the ICM surviving, would you post your results rather than the negative response approach? It keeps the flow of information intact with the problem, probable solution and results all tied together.
Good luck.
Fair enough.
While (I'll assume) you might have to get into the springs to make the curve correct for what GM asked for, I found one of the limitations of the HEI was the lack of being able to reduce the amount of centrifugal advance that's available.
It doesn't appear to apply to your application (which is great to have a drop-in distributor ready to go), but for me, all of the advance is front loaded (18-20° initial) and the centrifugal adds another 14° or so for the total. IIRC, an HEI has better than 19° baked in and no reasonable means to reduce that. Reasonable meaning not having to weld up the advance slot and work from there.
Once you're satisfied with the ICM surviving, would you post your results rather than the negative response approach? It keeps the flow of information intact with the problem, probable solution and results all tied together.
Good luck.
Its been in for a couple days, I’ve taken the car on a couple drives and let it idle in the driveway, etc and it seems to be fixed.
No stumble on acceleration, idling where I set it, starts right up and idles happily (hot or cold).
As far as my timing curve, etc, that’s a bit out of my range of understanding, just being frank. I know it has an adjustable advance canister but I didn’t even mess with it.
All of this makes me edgy when contemplating getting a programmable distributor so as to lose the weights, springs and vacuum can features I presently have.
I've an old and ancient MSD small cap distributor and a 6AL box. It all works very well but is tedious beyond belief to tune.
No HEI for me though but that's just a personal preference.
What do you do for a timing curve?
What is the issue with tuning it?
Coil Dwell is the only aspect that you have no control over.
Coil Dwell is the only aspect that you have no control over.
Before I sidetrack the OP's thread, what tuning are you referring to? If it's mine with old school technology (springs, weights, limiting bushing, adjustable vacuum advance cans, vacuum advance limiting plate....etc.) it's gets old working on these bits.
It was different when I had this at my disposal.
But I don't any more. Now I have to lean over the fender...
As for the HEI, the lack of a limiting bushing is problematic. More tedium to make it custom.
skinny z - your distributor is set up the same as mine is - as in NO ICM at all.
The magnetic pickup triggers the MSD box directly.
Yes sir. That would be the case.
It does add some complexity as it's not exactly a stand alone HEI.
That said, I know too that the CD box isn't necessary given what's available otherwise however as our OP has witnessed first hand, it can be incredibly frustrating working through this kind of stuff even without the added complexity.
That my combination of parts has done yeoman service for the more than two decades is what keeps it in the game.
Yes sir. That would be the case.
It does add some complexity as it's not exactly a stand alone HEI.
That said, I know too that the CD box isn't necessary given what's available otherwise however as our OP has witnessed first hand, it can be incredibly frustrating working through this kind of stuff even without the added complexity.
That my combination of parts has done yeoman service for the more than two decades is what keeps it in the game.
We are talking about an old-school 20+ year old MSD (non digital) box wired directly to the distributor's magnetic pickup coil via the green and purple wires from the MSD box.
Edit: it looks like you can also do this using the MSD digital box. Failure rate of those boxes ???
I've an MSD 8461 distributor which has been obsolete for years. It has no module and relies on the ignition box to do that job.
It's been replaced with the 8361. Same functionality though. It too requires an ignition box.
The ignition box is an MSD 6AL. Wired together they function like an HEI or other conventional electronic ignition. Just with no ICM.
My CD box is also old and has been superseded with the Digital 6AL.
I bought a cheapo HEI as a substitute but it doesn't have one particular tuning feature I'm looking for. That being an adjustable mechanical advance limit.
As far as HEI's go, I've read and heard plenty of success stories as stand alone units. Then again, plenty of stories such as your own that have people pulling out their hair.
For the same reason as the ICMs burning up regularly is the same reason I'm hesitant to move to a fully programmable electronic distributor. MSD and the Progressive offerings all have a printed circuit board under the cap. That's a really tough environment for electronics to survive. There are also many stories about the MSD unit giving up after minimal service. There goes 500 bucks! Poof. Literally.
Here's one programmable distributor that's caught my interest. But I think there's a risk involved. https://progressionignition.com/
We are talking about an old-school 20+ year old MSD (non digital) box wired directly to the distributor's magnetic pickup coil via the green and purple wires from the MSD box.
Edit: it looks like you can also do this using the MSD digital box. Failure rate of those boxes ???
Yep. Old school back in the day whiz bang technology!
That said, it's been as tough as nails. I heard the same isn't the case for more recently manufactured units. The again, what the hell is these days.
I better not have have jinxed myself with this praise for my old junk. I need it to work! Soon too.
I better not have have jinxed myself with this praise for my old junk. I need it to work! Soon too.
Welcome to my world.
The Progressive distributor sounds great "on paper", but I would be hesitant to use it unless the ignition coil was located outside of the distributor cap. Just my .
Last edited by NoEmissions84TA; 09-10-2023 at 06:50 PM.
I've an old and ancient MSD small cap distributor and a 6AL box. It all works very well but is tedious beyond belief to tune.
I was referring to the above statement...
And wondering as to what Tuning struggles were involved?
I personally find the MSD "Pro-Billet" Distributor very easy to work with the Mech. Advance, and very much LOVE the Limiting Bushing.
As far as the 6AL... it is just going to "Act" as the Set of Points and determine the Coil Dwell Timing and Multiple Ignition Strikes at lower Engine speeds.
It's the same thing as a HEI Module or ICM, but with a Rev-Limiter and Multi-Spark Discharge.
Coil Saturation is maximized for a given Engine Speed.
But doing so for one Cylinder is quite the task...
Unfortunately this Coil needs to deal with the speeds and demands of all 8 Cylinders.
That One Coil has to do a TON of very FAST work for all 8 Cylinders.
Comparing it to the easy job that a Coil on an LSx Engine would have...
The Progressive distributor sounds great "on paper", but I would be hesitant to use it unless the ignition coil was located outside of the distributor cap. Just my .
It's more about product support than anything else.
Bluetooth connectivity only. No laptop interface possible.
And WHO are Progressive and will they be around in 10 years time when I need help?
I was referring to the above statement...
And wondering as to what Tuning struggles were involved?
I personally find the MSD "Pro-Billet" Distributor very easy to work with the Mech. Advance, and very much LOVE the Limiting Bushing.
The only struggle Mr V is that leaning over the fender gets pretty old after a while.
The tuning is simple enough albeit tedious.
The mechanical curve wasn't too bad. I know where I'm going with that. It was the amount of effort I had to put in to dial in my vacuum advance. Lots and lots of back and forth with cause and effect and then further effect. More adjustments. But, I can say that sucker ran like it had EFI was it was all said and done.
The only struggle Mr V is that leaning over the fender gets pretty old after a while.
The tuning is simple enough albeit tedious.
The mechanical curve wasn't too bad. I know where I'm going with that. It was the amount of effort I had to put in to dial in my vacuum advance. Lots and lots of back and forth with cause and effect and then further effect. More adjustments. But, I can say that sucker ran like it had EFI was it was all said and done.
Honestly, working under the Hood, leaning over the Fender or Radiator Support is murder on my body...
Honestly, working under the Hood, leaning over the Fender or Radiator Support is murder on my body...
So I feel for ya!
Not enjoyable at all.
You should see some of the contortions I go through in a day's work. Being in industrial maintenance (as an electrician) for the last ten years has put me in some pretty bizarre situations. And I'm no youngster by any stretch.
My hobby shouldn't be the same!
Next up, crawling around on my back on a sheet of cardboard while I button up the bottom side of the old Camaro.
That is after I'm done leaning over the fenders doing the topside!
Thanks for listening....
09-01-2023, 03:03 PM
Welcome to my world.
. 
