Gets warm and quits running?

[Ford46]

The Cape Man asked me to post to see if help can be found for his issue:

Background: 1947 Ford, 59AB flathead , good carb with phenolic spacer, new (good) coil, crab distributor recently set up on distributor machine.

Issue: Runs great until temp get about half way on guage (warmed up but not hot) suddenly quits running. Wait 10-20 minutes will start up and go for awhile.

Looking for assistance, thanks.