HEI conversion benefits

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70Duster340 said:
Why is the 8 pin module be better than the 4 pin one?
I used shrink tubing on the spade connectors when I installed the module. Maybe not the best weatherproofing, but better than nothing.
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If picking parts, you also grab the GM coil and the cable which connects the 8-pin module to the coil, so no custom-wiring for that. The coil has a white wire for tach signal. Also clip the pickup wire and cable. The 8-pin module is inside the "small-cap" distributor. The pickup connector is not shielded but does have a locking clip. 8-pin modules will likely be available longer in the future since a 1985-95 GM part. The 4-pin is a 1970's part. In-between there were a few more GM HEI modules, like a rarer 7-pin. I don't know if the 8-pin has better tech, other than the input for spark advance, which you don't have to use. Read more on the megasquirt site.

A Mopar 1970's e-distributor will trigger the 8-pin (or 4-pin) module, since the same 2-wire VR sensor type (not later Mopar w/ 3-wire Hall-effect pickup). You must get polarity correct. Both will trigger it, but if wires are reversed the triggering will be erratic. I tested it by spinning the distributor by hand and flashing a timing lamp at the reluctor wheel. You should see the pickup teeth aligned with the mag sensor if correct polarity. Twist the pickup wires and keep them short so you don't get positive-feedback from the spark wires (self-sparks with engine off).
 
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I've not only covered the spade connectors with heat shrink tubing, but the wiring from the distributor to the coil and the wires to the module have been covered with plastic conduit.
 
70Duster340 said:
I have tried to research this topic both here and on the Internet, but I haven't found anything that will answer my question.

Once this conversion is done, can the ECU and the ballast resistor be removed?

I know there's purists here who would say I am blasphemous for contaminating a Mopar with GM parts, but if you can see your way to overlook my transgressions, I would be grateful.

Thanks
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I would look at a Progression Ignition distributor. They are a bit expensive, however they have a bunch of features built in. Mechanical and vacuum advance curves are programmed off a cell phone via Bluetooth. There is a built in MAP sensor that is used instead of vacuum. High vacuum is a low manifold pressure. There is a wire that can be energized for nitrous to retard timing 1° - 10°.
 
When you ^^^ don't know, you don't know.

Screenshot_20240228-214252_Gallery.jpg


Yes the ECU and the Ballast Resistor can be removed. The HEI and E-Coils run on straight 12 volts and they run cool.
☆☆☆☆☆
 
70Duster340 said:
Well, it's always been a hassle for me to get it right. It was just a thought.
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Under vacuum, you have less cylinder filling and the mixture doesn't burn as quickly. So it needs more timing to run efficiently. Unless you only run at idle and full throttle, your ignition system will need some way to provide this advance - either a mechanical advance diaphragm or an electronic system with a pressure sensor.
 
I don't believe I would have room for that. Looks like a hybrid between a Mopar distributor and a GM distributor cap.
 
70Duster340 said:
I don't believe I would have room for that. Looks like a hybrid between a Mopar distributor and a GM distributor cap.
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Often true that those GM-style coil-in-cap distributors are too wide, so interfere with the firewall. Also pricey. GM changed to an external coil in 1985, using their "small cap" distributor, even though their small-block had room for a coil-in-cap.
 
A GM module is basically a small MSD without multiple spark. You can mount it on the firewall ,fender ect. Lots of wiring diagrams on the web. It will eliminate the ballast resistor. All you need is a coil, a module and a heat sinc. Less than a $100. Spare module just in case. I doing 2 for my cars in case the MSD fails. Don't use that big cap.
 
I'm using the tan Mopar cap. I bought the bracket that fits under the distributor, along with the bracket that mounts the coil to the intake manifold.
 
Carnut68 said:
A GM module is basically a small MSD without multiple spark. You can mount it on the firewall ,fender ect. Lots of wiring diagrams on the web. It will eliminate the ballast resistor. All you need is a coil, a module and a heat sinc. Less than a $100. Spare module just in case. I doing 2 for my cars in case the MSD fails. Don't use that big cap.
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An MSD box is a bit of a different critter: It fires the coil by dumping 400 volts from a capacitor into the coil. HEI uses an electronic switch that behaves like points, but with variable dwell.

This has a few differences in practice. One, a tach that works with the stock ignition will work fine with an HEI. With the MSD, you may need an adapter, and should not wire the tach to the coil. Two, a coil optimized for an MSD will barely work with an HEI, although a stock type coil will work OK with the MSD. A stock coil with an HEI might not work as well as using a modern coil, but it will still do at least as well as it did with the stock ignition if not better.

Both get rid of the ballast resistor though.
 
for 10 degree timing retardation use a 5 pin module from a 81 turbo firebird or and turbo grand national...
 
yes if you can find one they come in at a mid price
but as with rubber products NOS is not necessarily best

the first versions from the mid 70s used electronics that needed to be protected with a perfectly matched condenser/capacitor or as Lucas did in the AB14 (Jaguar HEI ignition) used a clamping diode to hold any back emf on the primary to 300V.

modern ones if good quality do not need capacitor or diode protection

delco branded stuff is usually good.

dave
 
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