Hmmm, interesting conversation. I've owned my 54 3100 since 78, rebuilt the eng twice each time with a new thermostat last time in 87. The only over heat I've had was a timing issue. In all my years as a automotvie techincian I've never heard of drilling a t/stat to make a system work better.wasnt in tsb's or service manuals.. I don't get it.... .A few years ago I installed a coolant shutoff valve to the heater so that it didnt pump hot coolant thru the heater in the summer. Have never had a problem with a disrupted coolant flow causing eng warm up issues. It also helped to stop the small coolant leak in my heater core! I wont reexplain how the cooling system because in all the discussion it was explained and in my thinking as I read thru, there wasnt a problem except for the external issuse. I believe our brains overthink things and we over look the simple things. Always go to the basics and work your way up. Ive got stories of hours wasted to fix a problem that should have taken a few minutes. Some my own and some by others.
