[gr8dain]

Hello. Years ago (4?) we replaced the points distributor with an HEI. For some reason, we keep killing them. I am no electronics guru, so I am not great at diagnosing the real issue. But a couple of years ago, we put in the 4th HEI l. We thought we went with a quality unit as we got an MSD one. But it only lasted a little more than a year. I would like to get this run ing again (67 with the 327).

Before I put more money into another HEI (DUI?), is there a better option out there?

 

[jayoldschool]

Are you using a real GM HEI or some inexpensive Chinese one? Ran a full 12V wire?

On my 65, I simply converted the original to Pertronix, and ran a new 12V wire to the fuse panel. Starts right up, much more power.

 

[gr8dain]

Are you using a real GM HEI or some inexpensive Chinese one? Ran a full 12V wire?

On my 65, I simply converted the original to Pertronix, and ran a new 12V wire to the fuse panel. Starts right up, much more power.

The first few were cheap amazon specials my son was buying on his budget. The last one is an MSD made for the 327. Not a GM made unit. And yes, it has a full 12v running to it. But no spark coming out.

I got a used pertronix set up before we started down the HEI path 4 years ago. But it never worked. Being used, I chalked it up to the fact it was used and maybe broken. Might e worth a shot again. I still have the original distributor.

 

[62BillT]

I've heard good things about a Pertronix, but I'm keeping my Points !!

Been running Points for over 50 years straight.

 

[jayoldschool]

The ICM is a known failure point on any HEI. Test that first. Are you applying thermal paste compound under the ICM?

 

[gr8dain]

The ICM is a known failure point on any HEI. Test that first. Are you applying thermal paste compound under the ICM?

Yep. And I tested it by using a few spares from prior modules from the other dead HEI units. So no clue if those were any good either. I need to bench test them and the one in the current unit.

 

[Big Dave]

Two things kill transistorized ignitions: voltage variations and heat. The reason GM went to a CS (one wire) alternator was because the battery operated with an on board battery charger (the old SI alternator) couldn't maintain consistent voltage to the computerized sensors and controls on a computerized car. With an HEI the module that controls the ignition gets hotter and hotter the higher the RPM. Above 4,800 RPM the HEI misfires or stops working until the module cools off.



The reason every one dropped points originally and swapped over to HEI is because points bounce at high RPM and the contacts burn at an increasing rate once the "hard candy shell" (tungsten plating) burns off. People used to file the points but this removes that tungsten coating leaving the copper beryllium contact metal exposed. Another reason is the Corvette was the first to offer a capacitive discharge system instead of points back in the early seventies (it was a rebranded MSD 6AL) using an HEI as the breaker to trigger the ignition box. If it was on a Corvette every one wanted it.



Chrysler had an HEI ignition three years before GM did but every one hated it because of reliability issues and the fact that no one understood how it worked.



I used a Mallory four lobe dual point distributors (I had simultaneously 13 street/strip cars tagged and insured at one time) for years before I switched over to a Vertex mag on my trailered race car. The four lobes split the V8 into two Siamesed four cylinders as far as the ignition was concerted so the high RPM I ran back then (7,800-9,600 RPM) didn't affect the points the way it did in GM's dual point eight lobe distributors. Each contact point saw only half the engine RPM.



Another factor that affects old cars with HEI is poor grounds. If you don't have well grounded electrical components they can not be relied upon. The HEI ignition is very prone to this issue.



As I said transistors are animals that depend upon a rock sold voltage system as the difference of half a volt really affects the signal that the transistors receive, and as such the response you can expect out of it. This is why a CS alternator is a regulated power supply that is of better quality than many Chinese made computers use. The voltage never varies and it will out put it's full rated power (105 to 160 Amps) from just off idle engine speed. Unlike a SI system that runs off the battery constantly and used the alternator only to recharge the battery (which is why your lights dim to yellow at idle and brighten up again only after to get moving again).



Reverse polarity with a battery jump gone wrong and you bought a new HEI module. Same thing happens if someone doubles the voltage to get that dragging starter to spin over.

Big Dave

 

[gr8dain]

Two things kill transistorized ignitions: voltage variations and heat. The reason GM went to a CS (one wire) alternator was because the battery operated with an on board battery charger (the old SI alternator) couldn't maintain consistent voltage to the computerized sensors and controls on a computerized car. With an HEI the module that controls the ignition gets hotter and hotter the higher the RPM. Above 4,800 RPM the HEI misfires or stops working until the module cools off.



The reason every one dropped points originally and swapped over to HEI is because points bounce at high RPM and the contacts burn at an increasing rate once the "hard candy shell" (tungsten plating) burns off. People used to file the points but this removes that tungsten coating leaving the copper beryllium contact metal exposed. Another reason is the Corvette was the first to offer a capacitive discharge system instead of points back in the early seventies (it was a rebranded MSD 6AL) using an HEI as the breaker to trigger the ignition box. If it was on a Corvette every one wanted it.



Chrysler had an HEI ignition three years before GM did but every one hated it because of reliability issues and the fact that no one understood how it worked.



I used a Mallory four lobe dual point distributors (I had simultaneously 13 street/strip cars tagged and insured at one time) for years before I switched over to a Vertex mag on my trailered race car. The four lobes split the V8 into two Siamesed four cylinders as far as the ignition was concerted so the high RPM I ran back then (7,800-9,600 RPM) didn't affect the points the way it did in GM's dual point eight lobe distributors. Each contact point saw only half the engine RPM.



Another factor that affects old cars with HEI is poor grounds. If you don't have well grounded electrical components they can not be relied upon. The HEI ignition is very prone to this issue.



As I said transistors are animals that depend upon a rock sold voltage system as the difference of half a volt really affects the signal that the transistors receive, and as such the response you can expect out of it. This is why a CS alternator is a regulated power supply that is of better quality than many Chinese made computers use. The voltage never varies and it will out put it's full rated power (105 to 160 Amps) from just off idle engine speed. Unlike a SI system that runs off the battery constantly and used the alternator only to recharge the battery (which is why your lights dim to yellow at idle and brighten up again only after to get moving again).



Reverse polarity with a battery jump gone wrong and you bought a new HEI module. Same thing happens if someone doubles the voltage to get that dragging starter to spin over.

Big Dave

Wow. That was a lot of great info Dave. And I will definitely check on the grounds. But after reading all of that, what do you suggest as the right system for me as a nice cruiser? My son wants to eventually use it on the strip, but lots needs to be done first.

 

[Big Dave]

On my street cars I use a capacitive discharge ignition system with a magnetic trigger (either an HEI distributor with the HEI module disabled, or a crank trigger). I have two MSD 6ALs and a MSD 7AL-3 that I have used for over twelve years now. I have read reports that MSD shipped their manufacturing over to China, and the quality fell considerably. Couldn't say as mine were made in the USA. MSD invented the capacitive discharge ignition system for racing two cycle motor bikes which are hard on plugs.

GM later bought them out to use their devices to reduce emissions. Frequently reducing emissions and increased power go hand in hand as nothing makes more power than burning all of the gas you dump into a cylinder, or by making a head breathe better by raising the ports (Chevy's 1996-'04 "Vortec" heads), or mixing the gas and air to get complete combustion (Chevy's "Fast Burn" heads). All of these changes to early Chevy heads (designed in 1951) were advanced to reduce emissions: but they also increased horsepower.

A capacitive discharge ignition system burns the fuel more efficiently by firing the plug two to five times every power stroke. Even when at high RPM it only fires once, the spark has much more power as the juice to fire the plug comes directly from the battery, not from an HEI transistorized module. The bigger the number (6, 7, or 10) reflects the size of the caps inside the box and as such the power that they can soak up from the battery. A 10AL has enough power to kill you if the surge were to travel through your body (we are talking about amperage: as anything above 28 volts can kill you; and your plugs fire with thousands of volts, but very little amperage with points or HEI inductive ignitions). A 10AL system is the equivalent of a mag in power output, which is why they are used on race cars that used to rely upon magnetos. Advantage is to the capacitive discharge ignition system that doesn't rely upon a mechanical contactor to fire the plug (points) the way a mag does.

Big Dave

 

[gr8dain]

Thank you Dave.

 

[gr8dain]

I have replaced the points with pertronix, and have replaced that with HEI.

Went out the other day to test the HEI and it is fine now, but won’t start. Ran hot wire direct from the battery to the coil and it started right up. So I need to run a thicker wire from the ignition to the coil. The voltage is dropping from 12 to 10 something when cranking. Maybe the starter is drawing too much. Will check for connections first. But plan to run a thicker gauge wire from the fuse box to the coil.

 

[gr8dain]

So we ran a dedicated wire from the battery to a switch in the cab to the HEI and it starts right up. Tested the old wire and nada. So there is something with that. But it runs now. Se we will permanently mount the switch. Thanks to Big Dave and others for the assistance.

 

[jayoldschool]

Glad you got it sorted out!

 

[gr8dain]

Glad you got it sorted out!

Thanks. Need to just tidy up the wires.