[JSeery]

The hotter the better within the limits of other factors around the engine. With a pressurized system more modern engines are capable of running at higher temperatures. Gasoline engines are heat engines and any heat lost to the cooling system is lost energy. There are practical limits on a flathead in an enclosed engine compartment. 195 deg would be a good operating temperature to me, but 190 might work better in some applications. I would consider 180 to 185 as a minimum. In the early years there were limits imposed but non-pressurized systems and antifreeze types. In the later Flathead years Ford used a pressurized system and with better antifreeze increased the recommend operating temperatures stating better lubrication and increased efficiency.