I was brush hogging today with 8n (1947), and tractor suddenly lost power and the radiator overflowed. Temperature is in mid 60’s, and I had been mowing for about 45 minutes. Engine turns over now , but will not start. I’m letting it cool down now, but wondering what would be the most likely cause…
Thanks for any suggestions.

How tall is the stuff that you are mowing and how much debris has collected in the radiator?

The problem turned out to be vapor lock,I think, because it finally started after it cooled down, and is running well. The fan belt was pretty loose, though, and I wonder if could contribute to the heating of the gas line.
Your thoughts would be appreciated

I think you are dealing with a couple problems. The overheating can be caused by the loose fan belt. From my experience brush hoggin, the radiator fins can easily get clogged up.I have to clean mine after each mowing. Secondly, don't over look the ignition coil sitting right out in the front of the engine.. Often when they will stop producing spark when they get hot. They then start producing spark again when the engine cools.

My mistake on the front mounted coil. I thought you had a 9N.

A loose fan belt will definitely contribute to overheating.

The gas tank is vented, but the vent can get clogged with dirt. Some folks who are having issues like yours have drilled a 1/16" vent hole in their gas cap.