My dads truck (80 GMC) was originally diesel powered, I swapped in a 455 years ago. Today it didn’t start, no spark. It ran fine when I parked it 2 days ago. When I removed the cap I found the cap, rotor button, and the bottom of the coil melted. I have had this happen twice on my 69 Cutlass, I assumed it was due to using stock replacement parts with the MSD ignition. Upon MSD recommendation, I used their low resistance button. My dads truck is a stock rebuilt 70 with a HEI Ignition. What’s been happening lately?! Cars ran fine with HEI for 30 years. I’m glad it happened in my driveway , in 50 degree weather as opposed to the nasty snow and freezing cold.

Does anyone in readerland have a mid 70s service manual that shows the proper orientation of the advance plate, weights, etc of a Olds HEI distributor? And anyone have a recipe of parts that will give me about 20 degrees of centrifugal advance? I have a huge assortment of weights and plates, and access to a distributor machine. Thanks

 

The HEI has 20/21 degrees advance built into it. The plate position is maintained by the vacuum advance. You need to replace at the very least the cap, coil, and rotor, possibly the module.

 

I have never seen a melted coil, melted cap around the button yes. Something must be causing the coil to overheat. I'm no electrical guy, so I comment on what would make the bottom of a coil melt.

Eric

 

A poor connection is the usual culprit.

 

The bottom of the cap is melted, the rotor button is gone (all that remains is the spring embedded in some of the plastic from the cap) and the bottom of the coil has some obvious heat damage. I haven’t done any testing yet to see if it still functions electrically, I don’t think I would reuse it even if it tested good. It may be good now, but for how long? I’m just curious why I have seen this happen recently.