Help figuring out miss in an HEI 350?

[eric8]

Well take this story for what it’s worth, I had a no start condition as well that came out of nowhere with an HEI. It made me pull my hair out too. I replaced the module with a U.S. made Standard Motor Company module (apparently the same as Echlin). That immediately fixed the no start condition, but when I revved over 2k rpms it would miss and backfire like crazy.

Sent that module back and ordered the following kit from Proform. They make the distributors that come in the GM performance crate motors. Not shown in the picture, but the kit also came with an assortment springs, and the GM “ZZ series” crate motor center cam and weights. A weak coil can show up good when you ohm it out but cause all kinds of problems frying modules and making them do wonky things. This kit basically replaces everything in the equation except for the pickup coil. Whatever was wrong, it fixed all my issues. Also make sure your distributor has a good ground through a bare distributor hold down clamp to the block. Look for any obvious signs of chafing or wire breakage on the wires going to the pickup coil. The movement of the vacuum advance mechanism back and forth can weaken the wires and cause intermittent connections. Ensure a full 12v at the HEI wire that plugs in to the cap just to rule out a voltage drop.