[Joe Immler]

I have never understood temperature variations in a flat head. For a time I lived in Ca. and we would tour up the mountains to escape the heat down below. After reaching the top my engine temp would be 200 to 210 degrees with 180 thermostats. On the way back down the temp would drop to around 100 degrees. I had an SW mechanical gauge. I know the thermostats worked because I would test them. Never understood this.
Now I am in Ohio. The other day the ambient temp was 40 degrees and I drove for about 40 miles. Engine temp never got above 110.
Put a half sheet of cardboard in front of the radiator to raise the engine temp like we did "back in the day" so the heater would work.