HEI ignition conversion

[Bitsyncmaster]

Absolutely true. I don't think you'd want to use a coil with tooooo low a primary resistance.

I looked at the data sheet on the MC3334 part. It looks like the part was designed to use our 800 ohm pickup coil which is good. But I don't like the idea of replacing our coil resistors with the heat generating coil driver in the the part. I don't want 50 watts of heat in the cubby hole behind the drivers seat. Much better having that heat back in the engine compartment. You could probably find the correct coil to limit that heat.

That part is hard to find here in the USA.

[Raphael]

After some hours of road test I can attest :
- the GM module doesn't generate high temperatures. the little heatsink that I use (see pics in the first message) is just warm after hours of driving. you can hold it in your hand, and the ambiant temperature of the compartment behind the seat is normal.
- I removed the ballast in order to supply a MSD Blaster coil with full 12v and it won't overheat either. I performed several safety tests , stopping often to check temperatures of both coil and module. everything was normal.

[Bitsyncmaster]

After some hours of road test I can attest :
- the GM module doesn't generate high temperatures. the little heatsink that I use (see pics in the first message) is just warm after hours of driving. you can hold it in your hand, and the ambiant temperature of the compartment behind the seat is normal.
- I removed the ballast in order to supply a MSD Blaster coil with full 12v and it won't overheat either. I performed several safety tests , stopping often to check temperatures of both coil and module. everything was normal.

Good info. What is your primary coil resistance?

[Raphael]

Blaster's primary resistance is 0.7 Ohms.
I had doubts too, that the setup would withstand full voltage so I ran it with the stock ballast at first. Then I received infos from MSD's tech line stating that the coil would work fine combined with a GM module.
It was worth a try , at least. And in the end, it works pretty good without excessive heat.
So I think I get a good combination.
Pertronix coils have a primary resistance of 1.5 Ohms for those who want to be safe ( same total resistance of stock blue coil + ballast )

[nkemp]

It doesn't sound like a problem but if it were, we could mount the module on a heat sink in the engine compartment... possibly where the resistors currently reside. Correct me if I'm wrong but the GM module is weather proof. I believe GM actually did this on some models.

[Raphael]

yes of course, my first idea was to mount it in place of the ballast. the only modification would be to add just one wire between the setup and the coil.
Then I installed everything in a stock Bosch ECU for conveniency during tests ; so I could plug and unplug at will for comparison and in case it would turn bad lol
but now I think the actual setup will stay for good.

[Raphael]

GM actually put the module on a heatsink on the firewall of 90's GM trucks. that's this particular heatsink I used here ( AD Delco # 10474610 ).

[nkemp]

Then I installed everything in a stock Bosch ECU for conveniency during tests ; so I could plug and unplug at will for comparison and in case it would turn bad lol
.

I like the idea of being able to go back to stock should one ever want to (although I can't really think of a good reason). It would be nice if we could track down that connector or another module that used that connector and was available for dirt.

When I was investigating this module, I read that some use trailer light connectors to plug into the original wiring. An interesting idea and a heavy duty inexpensive connector. It could be wired in parallel to our connector (just make sure to unplug the Bosch unit.

[stevedmc]

Byrne Heninger and Bill Robertson used dead Bosch modules to make plug in adapters for their Ford Duraspark modules:

[nkemp]

The trouble is coming up with the failed modules or knowing what to pull at the junk yard.