Hei conversion Intermittent start?

Sorry, but I lost it when I saw wiring setup laying on top the plug wires and the coil wire laying on the fender.

It is possible now that the HEI has been damaged. Failure could be caused by insufficient heat sink, open circuit sparking or miss-connection.

When cranking timing reference pulses are irregular as the starter motor speed varied with engine compression. The HEI module extends dwell and is a current limit mode. This mode dissipates the most heat. When the engine is running, the dwell timing is controlled to charge the coil without going into current limit. I am guessing that a flate plate heatsink made of aluminum need to be about 1/4 thick and 2 x 4". It might work with less if it is bolted to the body in a cool place.

Wiring is important! The pickup side of the HEI receives signals from the distributor of only a few volts peak to peak when cranking, and they will be much higher at high RPM. Polarity matters, and short twisted leads are essential to prevent false triggers. A false trigger keeps ignition busy, so spark cannot be provided when desired.

Working with electricity is predictable. It involves not only correct connections, but things in correct physical placement and proximity to other sources. While things like plug wire have insulation for electric fields, there are magnetic fields that radiate.

Maxwell's Equations are helpful for those who wish to know more about electromagnetic field theory.