HEI issues

[player1up]

I converted my /6 to a hei system a few months back and I've been having this issue with missfire when the engine is hot or more like something is getting hot and cutting out. I've tried 5 different HEI modules 4-pin, 7-pin, and an 8-pin accel, and they all do the same thing when the temp under the hood gets too hot (1/3 up the gauge), no power, sputtering, pops thru the carb. I have both systems in the car at the moment (only one hooked up at a time) so I can test it. Does this sound like a bum coil? as all of the modules have the same symptoms....and if it is the coil how do I get the correct coil (resistance) for the module or does it matter? The current coil is a solid plastic type 12v, .9 ohms primary and 8.5kohms secondary.

My next course of action is to bust out the heat gun and see if I can make it happen while the engine is cold...

 

[dgc333]

Could be the coil or it could be the pickup in the distributor.

Also, what are you using for a ballast resistor? Contrary to a lot of the internet postings using a GM HEI module with a mopar coil or a coil intended to be used with a ballast still needs the ballast resistor. GM designed a system (ecu and coil) that did not require the ballast but using the module with another coil that uses the ballast still requires it. This problem you are having could very well have been caused by not running the ballast.

 

[player1up]

Welp, It's not a bum coil I'm using the GM epoxy coil, and tonight I tested another 12v coil that I had kicking around from a late model magnum motor, and still the same symptoms when hot. As of now it runs better with a relay and clean power coming right from the battery, but time and heat will tell.
Hmmmm $20 for a pick-up coil or $40 for the whole dizzy?

 

[doktor_x]

Is the module mounted solidly (with thermal grease) to a good heatsink? I'm not sure whether you've tried swapping another module into the circuit while the temperatures are still elevated under the hood. Those modules do some strange things (and often burn up) when they get too warm.

I may be running in the wrong direction, but it's a possibility to explore.

 

[JR]

I ran the HEI set up on my daily driver 360 for 7 years and on a slant for 3. You have to make a bracket for the HEI unit that lets air get under it and mount it on the fenderwell away from the motor they are very heat sensitive.

Use a 4 pin HEI and a MSD Blaster 2 type coil it gets way too hot for a stock coil. I had my plugs gapped at 40-45 when I ran the HEI set up.

 

[player1up]

Well, another module and a different coil provided the same misfire....so as I'm swapping parts I decided to add a test wire from the battery for my power source, and wouldn't you know the issue went away.. so I added a relay to power the module and coil and 18hrs later and 3 solid test drives and it's still running strong. go figure..