The 70%/30% mixture was used in most water cooled aircraft engines in WWII. Winter operations and romping about above 25,000 feet requires ethylene glycol. The racer uses distilled water and 10% glycol plus Redline Water Wetter or 1/2 teaspoonful of Dawn Dish soap. A 22 pound Stant lever cap. In the fall I used a 160 degree thermostat with 3 1/8" holes through the rim. Thermostats fail in the closed position. Those three holes can cool the engine at less than full throttle. We usually have to tape over about 1/3 of the radiator to hold 160 degrees.

The three holes also help remove air from the system faster.

 

Lynn E. Hanover

 

Regarding coolants of both types, what is the current thinking of running a thermostat, yes , no or possibly?  Neil.