My 350 chevy on a irrigation well was running at 220 and would shut off at 230*
I reset the timing by putting it under a load and turned the distributer until rpm maxed out. Thought I had it fixed, but to day with 93* temp engine shut down at 230*.

Cranked it up and turned the fuel adjustment  (impco mixer that I ran on pickups back in the early 70's) toward lean (L) and as the rpm fell off I would open the throttle until I got to the point it wouldn't carry the load at 1700 rpm. Backed it up from there until it would carry the load and left it..........figuring I would burn it up right then and there.

Came back in about an hr. and the temp is on 180* and stayed there all day.
So a rich mixture caused more heat to build in the engine, the opposite from what I thought.
Thanks again,
John