Cooling comes via an ’83-‘86 VW GTI racing radiator measuring 300 x 500 x 40 mm and laying about 30 degrees from horizontal in the an SC-266 under-cowl scoop (that’s an aftermarket automotive hood scoop from up22.com cut-to-fit by Williams). An auxiliary 11-in. Perma-Cool fan on the backside of the radiator comes on automatically at high temps, which so far has only been during ground testing without the prop in place. The scoop opening is 26 sq. in. and the exit over 60 sq. in., plus auxiliary louvers for plenty of draw. It works great says Williams, noting coolant temps run consistently right at the stock thermostat setting of 197 degrees F.