Interesting. It's a new high output GM type starter and solenoid from Napa. I have an old one that worked fine when I pulled it out years ago. I could toss it in to see if the napa starter is defective.

That brings a couple of questions to mind:

Is the solenoid the part that heats up and won't work or is it the starter windings? The reason I ask is that the solenoid does kick in, but the starter won't turn the engine fast enough.

Which heat shield is a good one? I'd like to get one in any case.

I forget, is it that when the timing is too far advanced or retarded that it will have the same symptoms? I'm trying to think ahead a little if the starter improves things but doesn’t eliminate it.