"Pretty warm" is not a temperature reading. Try checking the temperature of the cylinder head casting in the area of the thermostat housing with a laser thermometer as the engine is warming up. Does your thermostat have a "jiggle pin" or a small hole drilled in it to prevent an air lock from forming?
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!