I’ve been following this subject closely as well.

My cooling system design follows the P-51 very closely (Long-EZ.) The P-51 drawings were scaled down to fit my airframe.

We have an A/P within our EAA Chapter that works on the P-51 Gunfighter. I’ve asked him many questions about how the cooling system works on that aircraft. I was surprised to learn that there is no thermostat in the P-51. The coolant temps are regulated by the position of the radiator exhaust door.

In another application (Tim England’s V-6 Velocity) a coolant/oil heat exchanger was used. This performed a double function. It cooled the oil during the summer but it also kept the oil at an acceptable operating temperature when flying through colder air (such as winter and/or high altitude.)

I’m not advocating replacing an oil cooler with a coolant/oil heat exchanger (although this is the system used by Mistral Engines) but it would be a nice addition to help stabilize oil temps in colder weather.

T Mann