Troubleshooting GM HEI

I realize a lot of you guys have moved away from the old GM HEI distributors, but I thought I throw this out for the guys still running them.

Last week I went out to start the El Camino (500 Caddy powered), it fired right off as usual and idled smooth also as usual. When I went to give it some gas however it surged horribly at anything above idle. I’d already seen this one other time so the first thing I tried was pulling the hose off the vacuum advance…..the surge went away. I pulled the El Camino into the shop and changed out the distributor for a spare I had and did a postmortem on the one I took out.

I found what I figured I would, a broken wire between the pickup coil and the module plug. As the pickup coil is stationary and the module is attached to the breaker plate the wires flex as the breaker plate moves back and forth. In this case the flexing eventually caused the wire to break, at idle with the wire relaxed the 2 ends of the broken wire made contact, but when vacuum was applied and the breaker plate rotated the wire pulled apart.

Just thought I’d pas this along in case anybody else runs into it in the future.


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Yep, I've seen that happen also. Most of my failures are modules going bad, though.

Mike

I saw that once: the little tit broke off th pick up coil, allowing the. Coil to rock back and forth. The insulaton cracked on both wires. The result was intermittent miss when the cracked wires would short to ground. I always had wondered what could break the tit, now I know.

Having the same problem as the rest of the world..There seems to be no answer..May go back to points dist..Tired of buying mods

Had that happen to a 305 Olds. No longer available 4-wire module, had to find another distributor.