GM ignition module conversion

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I have this I copied a while back for some info. if it helps.
To help clear up some confusion about HEI ignition systems, I have written some answers to commonly asked questions.

What is HEI?
HEI is a term used by GM that stands for High Energy Ignition. An HEI ignition system uses a highly efficient control module that is capable of switching a large amount of energy to the spark plugs AND a high power coil with low primary resistance that can provide that power. Power is current, voltage and time so if any of these factors are lessened, the power available to your plugs is decreased.

Are all electronic ignition systems HEI systems too?
No. The original Chrysler electronic ignition system is not an HEI system. First, it requires a ballast resistor in the primary circuit to decrease the power going through the control module. It was not designed to switch that much power and will fail if you run it without the resistor. Second, it uses a relatively low power coil. The old canister style coil can't put out the kind of power that an HEI system can without overheating the coil.

Is Pertronix an HEI system?
Ignitor I
The Pertronix Ignitor I is not HEI becuase it requires a minimum of 1.5 ohms primary resistance similar to the original Chrysler system.
Ignitor II
From the description of the Ignitor II, it sounds like it uses technology similar to the original GM module, so qualitatively, it may perform similarly. I have never used the Ignitor II to compare it directly.

What is the difference between an HEI coil and a canister style coil?
An HEI coil has very low primary resistance, typically in the range of .1 to .4 ohms. This is the total resistance of the primary circuit and allows a large amount of power to build in the system. A canister style coil typically requires from 1.0 to 1.5 ohms to survive without overheating. The coil used in HEI systems is a different design, called an E-core because of its shape. This design of coil is inherently more efficient, resulting in less noise (good for computer systems) and less heat. The picture below on the left is a typical canister style coil, and the one on the right is an E-core coil. Both pictures are from www.summitracing.com


Can I use an HEI coil on my Chrysler electronic ignition?
Yes you can because both systems use coils with primary resistances of around .5 ohms. However, you must retain the ballast resistor for the control module, so the total resistance will still be around 1.5 ohms and the power that your coil will put out will be limited by it.

If I use a GM HEI ignition module, can I remove my ballast resistor?
Yes you can as long as you either
1. Use an HEI E-core coil with low resistance or
2. Use a canister coil with 1.0 to 1.5 ohms resistance. This resistance is required for the coil, not the ignition module.
You must retain the ballast resistor if you wish to
3. Use the stock Chrysler coil with .5 ohms resistance. The ballast resistor here will prevent the stock coil from overheating.
The HEI ignition module enables you to use less primary resistance, but will function fine if you wish to use more resistance.
 
Kendog 170 said:
I have this I copied a while back for some info. if it helps.
To help clear up some confusion about HEI ignition systems, I have written some answers to commonly asked questions.

What is HEI?
HEI is a term used by GM that stands for High Energy Ignition. An HEI ignition system uses a highly efficient control module that is capable of switching a large amount of energy to the spark plugs AND a high power coil with low primary resistance that can provide that power. Power is current, voltage and time so if any of these factors are lessened, the power available to your plugs is decreased.

Are all electronic ignition systems HEI systems too?
No. The original Chrysler electronic ignition system is not an HEI system. First, it requires a ballast resistor in the primary circuit to decrease the power going through the control module. It was not designed to switch that much power and will fail if you run it without the resistor. Second, it uses a relatively low power coil. The old canister style coil can't put out the kind of power that an HEI system can without overheating the coil.

Is Pertronix an HEI system?
Ignitor I
The Pertronix Ignitor I is not HEI becuase it requires a minimum of 1.5 ohms primary resistance similar to the original Chrysler system.
Ignitor II
From the description of the Ignitor II, it sounds like it uses technology similar to the original GM module, so qualitatively, it may perform similarly. I have never used the Ignitor II to compare it directly.

What is the difference between an HEI coil and a canister style coil?
An HEI coil has very low primary resistance, typically in the range of .1 to .4 ohms. This is the total resistance of the primary circuit and allows a large amount of power to build in the system. A canister style coil typically requires from 1.0 to 1.5 ohms to survive without overheating. The coil used in HEI systems is a different design, called an E-core because of its shape. This design of coil is inherently more efficient, resulting in less noise (good for computer systems) and less heat. The picture below on the left is a typical canister style coil, and the one on the right is an E-core coil. Both pictures are from www.summitracing.com


Can I use an HEI coil on my Chrysler electronic ignition?
Yes you can because both systems use coils with primary resistances of around .5 ohms. However, you must retain the ballast resistor for the control module, so the total resistance will still be around 1.5 ohms and the power that your coil will put out will be limited by it.

If I use a GM HEI ignition module, can I remove my ballast resistor?
Yes you can as long as you either
1. Use an HEI E-core coil with low resistance or
2. Use a canister coil with 1.0 to 1.5 ohms resistance. This resistance is required for the coil, not the ignition module.
You must retain the ballast resistor if you wish to
3. Use the stock Chrysler coil with .5 ohms resistance. The ballast resistor here will prevent the stock coil from overheating.
The HEI ignition module enables you to use less primary resistance, but will function fine if you wish to use more resistance.
Click to expand...
Thanks for this! I also have a 1.5 ohm PerTronix coil, I’ll change it out. Solves my question.
 
Easiest is to use the 1985-95 GM 8-pin HEI module and cable and coil which goes with it. Also grab the 2-pin pickup connector. Many posts. If you prefer more Mopar, could use a Magnum V-8 coil, which is a similar e-core type, but would have to make your own primary cable.
 
If you want the best [ most spark energy, 0.060" plug gaps ] from the HEI module, use a 0.4 - 0.6 ohm E core coil, such as MSD #8207 or similar. Just because you are using the GM module with a canister coil does NOT mean the bal res can be omitted. Most canister coils that are used with inductive ign [ HEI, Chrys ECU etc ] are designed to be used with a bal res. This is because the coils are designed to work on 7-8 volts, NOT the full 12v like an E core coil. The coil can overheat & fail if used without a bal res. The bal res also reduces the spark energy.
So check to see if the coil requires a bal res.
 
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