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......OTOH Our car has one of, if not the hottest underhood temperatures around. Especially the big blocks. I'd be concerned about the electronics not liking 175-200 degree temps.
And yet the old HEI system from 75 continues to function......
Exactly! You can be sure that GM did some hot weather durability testing and that is one of the best features of the HEI, Pretty sure they epoxy encapsulated it to enhance temp durability. And yet the module still must be screwed to a metal heat sink or it will fail. It cannot hang in mid-air.
OTOH all the fancy computer ignition modules being put into distributors today do a lot more functions and generate a lot of heat themselves. Even touch a MSD box that has been running? They get hot! Why do you think Nascar runs two of them? Too unreliable. Do they run two of anything else in a race car? And failure mode is sudden and absolute, consists of works one minute and completely dead the next.
If I switch to electronic, and I probably will, it will probably be to a small-cap HEI system, not Pertronix, MSD, etc. Because the electronics will fail, it's just a matter of time and when, and it will leave me stranded. Murphy says it will be at the worst possible time. But I can keep a spare HEI module in the car and change it in 2 minutes flat. My .02 I'll go magentic pickup, HEI, small cap distrib, high powered coil, and keep the Ignition shield.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by leigh1322
Exactly! You can be sure that GM did some hot weather durability testing and that is one of the best features of the HEI, Pretty sure they epoxy encapsulated it to enhance temp durability. And yet the module still must be screwed to a metal heat sink or it will fail. It cannot hang in mid-air.
OTOH all the fancy computer ignition modules being put into distributors today do a lot more functions and generate a lot of heat themselves. Even touch a MSD box that has been running? They get hot! Why do you think Nascar runs two of them? Too unreliable. Do they run two of anything else in a race car? And failure mode is sudden and absolute, consists of works one minute and completely dead the next.
If I switch to electronic, and I probably will, it will probably be to a small-cap HEI system, not Pertronix, MSD, etc. Because the electronics will fail, it's just a matter of time and when, and it will leave me stranded. Murphy says it will be at the worst possible time. But I can keep a spare HEI module in the car and change it in 2 minutes flat. My .02 I'll go magentic pickup, HEI, small cap distrib, high powered coil, and keep the Ignition shield.
The actual GM/Delco HEI distributor/coil/module system was designed (and tested/validated) for operation at 125C/257F ambient temperature. I have no idea what temperatures a lot of the aftermarket systems are designed to continue to operate at.
Regarding a small-cap HEI system, are you talking about an aftermarket unit "borrowing" the HEI name, a modified older Delco distributor, or what?
Well long story. I like the reliability of the HEI system.It's good to know it was well tested, I assumed it was. They run for years. I'd say it's fair to assume the aftermarket does not test as hard as GM.
But I do want to keep my small tach drive distrib, not install a "large" HEI, and not have to spend a thousand $ converting to GM T.I. either. I have read of "sudden failures" online from almost all the aftermarket conversion products: MSD, Pertronix, breakerless SE, Mallory, optispark, even the T.I. but not the HEI. I investigated a lot of them while I was blue-printing my distributor, and decided not to buy any of them. Stayed with points for now.
Sooo then I ran into this guy online: David Ray https://www.davessmallbodyheis.com/
He is a retired engineer, and he can custom modify my stock small cap 72 Vette distributor and turn it into an HEI. He basically installs GM HEI parts into my distributor. Obviously the coil is external and in this case so is the module. All that goes inside is the magnetic pickup and pole piece.
Unfortunately right now he is not accepting "jobs" do to a hand injury. Since he is currently incapacitated I have been e-mailing him off & on, and talked to him once or twice. He saw what I did online, and said I could basically do this myself. I need to figure out exactly what conversion parts he is using. It might be a MSD magnetic pickup trigger. I am not as sure about the pole piece. That could be GM or MSD. Other than that (what $100 in parts) and a $20 HEI module and your done. Doesn't sound too bad does it?
(Both he and others have said the $100 Chinese versions available online are not worth trying)
I do not have a numbers matching car, or distributor, so what's the harm? At least it will LOOK stock. And I can keep the chrome shielding.
I like the GM 50,000 mile reliabilty end of it, the "anywhere" module availability, and I could easily keep a "spare" module in the glove? box/bin.
I'll definately be calling him again soon, to see if his hand has recovered yet, and if not I think this time I'll probe deeper so I can get it done myself.
I have got an entire car to rebuild, so I thought I would just wait a little while. But maybe it's time for another call.
What do you think? Sound worth pursuing?
HEI module mounts externally to a heat sink, engine block, metal firewall, or Chrome Shielding or bracket in my case. Best part is Zero permanent mods to distributor.
Last edited by leigh1322; Apr 26, 2020 at 08:26 PM.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by leigh1322
Well long story. I like the reliability of the HEI system.It's good to know it was well tested, I assumed it was. They run for years. I'd say it's fair to assume the aftermarket does not test as hard as GM.
But I do want to keep my small tach drive distrib, not install a "large" HEI, and not have to spend a thousand $ converting to GM T.I. either. I have read of "sudden failures" online from almost all the aftermarket conversion products: MSD, Pertronix, breakerless SE, Mallory, optispark, even the T.I. but not the HEI. I investigated a lot of them while I was blue-printing my distributor, and decided not to buy any of them. Stayed with points for now.
Sooo then I ran into this guy online: David Ray https://www.davessmallbodyheis.com/
He is a retired engineer, and he can custom modify my stock small cap 72 Vette distributor and turn it into an HEI. He basically installs GM HEI parts into my distributor. Obviously the coil is external and in this case so is the module. All that goes inside is the magnetic pickup and pole piece.
Unfortunately right now he is not accepting "jobs" do to a hand injury. Since he is currently incapacitated I have been e-mailing him off & on, and talked to him once or twice. He saw what I did online, and said I could basically do this myself. I need to figure out exactly what conversion parts he is using. It might be a MSD magnetic pickup trigger. I am not as sure about the pole piece. That could be GM or MSD. Other than that (what $100 in parts) and a $20 HEI module and your done. Doesn't sound too bad does it?
(Both he and others have said the $100 Chinese versions available online are not worth trying)
I do not have a numbers matching car, or distributor, so what's the harm? At least it will LOOK stock. And I can keep the chrome shielding.
I like the GM 50,000 mile reliabilty end of it, the "anywhere" module availability, and I could easily keep a "spare" module in the glove? box/bin.
I'll definately be calling him again soon, to see if his hand has recovered yet, and if not I think this time I'll probe deeper so I can get it done myself.
I have got an entire car to rebuild, so I thought I would just wait a little while. But maybe it's time for another call.
What do you think? Sound worth pursuing?
HEI module mounts externally to a heat sink, engine block, metal firewall, or Chrome Shielding or bracket in my case. Best part is Zero permanent mods to distributor.
That's the basic system I've been running in my '69 the past 35 years. I converted my stock distributor to a variable reluctance pickup coil, and that signals an HEI module I have mounted under the ignition shielding, and the HEI module then controls/switches the stock can coil. The system has been stone reliable for a lot of years and track days, and I get great plug life with this setup.
I'm familiar with Dave. We've had several technical discussions over the past couple years (I'm a retired GM Ignition/ECM design engineer.). Bit of advice: Don't tell him we've had this or any discussion. He might think we're good friends, and that won't buy you any good will with him.
Well...... Maybe you are the better one to contact to convert mine?. Or advise me? IIRC he uses a MSD trigger. I am OK with that and could likely figure out how to mount it in the correct spot. Its the pole piece I have questions about.
BTW he got bit by a brown recluse spider, and has had multiple hand surgeries, so I don't know if he'll ever be the same, and I would just as soon not bother him.
Last edited by leigh1322; Apr 26, 2020 at 09:28 PM.
Exactly! You can be sure that GM did some hot weather durability testing and that is one of the best features of the HEI, Pretty sure they epoxy encapsulated it to enhance temp durability. And yet the module still must be screwed to a metal heat sink or it will fail. It cannot hang in mid-air.
OTOH all the fancy computer ignition modules being put into distributors today do a lot more functions and generate a lot of heat themselves. Even touch a MSD box that has been running? They get hot! Why do you think Nascar runs two of them? Too unreliable. Do they run two of anything else in a race car? And failure mode is sudden and absolute, consists of works one minute and completely dead the next.
If I switch to electronic, and I probably will, it will probably be to a small-cap HEI system, not Pertronix, MSD, etc. Because the electronics will fail, it's just a matter of time and when, and it will leave me stranded. Murphy says it will be at the worst possible time. But I can keep a spare HEI module in the car and change it in 2 minutes flat. My .02 I'll go magentic pickup, HEI, small cap distrib, high powered coil, and keep the Ignition shield.
Well, yes & no
Look at 96-up vortec motors ... their HEI module not inside OE phenolic resin dist housing (aftermarket dist are alum) ...but is screwed to a finned alum heat sink ...on a bracket along w/ coil, above intake, passenger side ... you could retro-mount it anywhere.
-add-
BTW ... above vortec components seem as robust & trouble-free as '75 HEI ... However,
the vortec distributor's "pickup" is actually a cam position sensor while the ignition "trigger" is at timing cover in a "crank-fire" configuration.
Well, yes & no
Look at 96-up vortec motors ... their HEI module not inside OE phenolic resin dist housing (aftermarket dist are alum) ...but is screwed to a finned alum heat sink ...on a bracket along w/ coil, above intake, passenger side ... you could retro-mount it anywhere.
-add-
BTW ... above vortec components seem as robust & trouble-free as '75 HEI ... However,
the vortec distributor's "pickup" is actually a cam position sensor while the ignition "trigger" is at timing cover in a "crank-fire" configuration.
OH I do like that heat sink. It even looks pretty. I am going to have to find me one of those....
The technical know-how on this forum is great!
OH I do like that heat sink. It even looks pretty. I am going to have to find me one of those....
The technical know-how on this forum is great!
well ... there one is at that $35 fleabay link ... cheap enough ... and that includes a matched coil & module ...
... dunno, but perhaps the '75 HEI pickup will trigger the Vortec module? ... dunno
Maybe Mike 69427 would know.
these days, vortec modules probably on-shelf more places than '75 HEI modules ... about as cheap too
here's youtube on R&R vortec module
Jack, the duty cycle and dwell times with coil paks would be different "I think."
As stated, I would want Mike to decide.
Since an HEI module works with it, I just do not see an advantage/need.
If I ever get time, I might try it next winter.
Too much going on right now.
saw this a couple months ago, looks pretty cool, but yeah not sure about the reliability. Interesting though, might be fun to play with. But they are not cheap!
saw this a couple months ago, looks pretty cool, but yeah not sure about the reliability. Interesting though, might be fun to play with. But they are not cheap!
You sure did Jim; Thank You ! My short-term memory's evasion tactics are improving.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by jackson
well ... there one is at that $35 fleabay link ... cheap enough ... and that includes a matched coil & module ...
... dunno, but perhaps the '75 HEI pickup will trigger the Vortec module? ... dunno
Maybe Mike 69427 would know.
these days, vortec modules probably on-shelf more places than '75 HEI modules ... about as cheap too
here's youtube on R&R vortec module https://www.youtube.com/watch?v=Qws2hpduL5Q
We've got an apples and oranges thing going on with this. The HEI module has multiple circuit functions built into it (AC input waveform processing, dwell time control, primary current switching, and primary current peak level control), as it's made for stand-alone ignition functions. The ICM module in the video differs, as it's made to work with an ECM. The ECM does all the all the fancy stuff (input signal processing and dwell time control), while the ICM just does the simple task of switching the coil on and off (following the square wave input signal), and limiting the maximum primary current during those dwell times. Two different applications and input signal requirements.
Jack, the duty cycle and dwell times with coil paks would be different "I think."
As stated, I would want Mike to decide.
Since an HEI module works with it, I just do not see an advantage/need.
If I ever get time, I might try it next winter.
Too much going on right now.
Jeff, yea maybe so ...maybe Mike knows ? Probably knows more about this stuff than any ten of me.
The L31 V8 vortec's crank-fire has only One coil But has a 4-segment crank reluctor between damper snout & crank sprocket ...
... its crab cap distributor still distributes via rotor-cap, 8 sp wires ...but No mech or vac advances ...
... but the sensor inside it not an ign module ... it's a cam position sensor ... PLUS an under-hood ECM tied to all of it somehow.
We've got an apples and oranges thing going on with this. The HEI module has multiple circuit functions built into it (AC input waveform processing, dwell time control, primary current switching, and primary current peak level control), as it's made for stand-alone ignition functions. The ICM module in the video differs, as it's made to work with an ECM. The ECM does all the all the fancy stuff (input signal processing and dwell time control), while the ICM just does the simple task of switching the coil on and off (following the square wave input signal), and limiting the maximum primary current during those dwell times. Two different applications and input signal requirements.
Just thinking out loud, but we should have Motertrend TV have Lars test one on his mule and then a test drive with a C3 for 200 miles. Better yet, a quick run up to Pikes Peak!
Now that would be a program worth watching! We could have Mike and Jackson do the install under Lars supervision.
Ok I'd like to get some feedback from you experts out there. I was seriously thinking about duplicating the HEI components in the small-body points style cast iron C3 tach distributor housing. It has been done for 40 years by David Ray, (and others) but his current health won't allow him to build one at the moment. Here's the recipe:
It doesn't seem that hard to me, and it would have the great HEI trigger/module reliability, with a stock distrib & oil filled coil. It would look 98% stock. The only machining required would be to turn down the points and place the reluctor on it. It's completely reversible besides that part, and I already have a spare.
I defer to Mike about the circuitry.
As for me, I would just jamb the repop TI guts into a stock tach drive and done. Too much BS for little to nothing gained.
The module mounting, I defer to Mike also.
I actually thought about puttinga TI on it.
Where could I find one one and not spend close to a $1000?
I could do this for $100 or so, it's functionally the same, and the HEI module is an improvement over the original TI system, and more reliable than any other module on the market.
A pertronix is the only other candidate I would consider, and then I could add a rev limiter. But I read enough breakdown stories I would feel obligated to carry a spare..
