RE: Screamin Demon X2
My Nelson lands pretty cool after a full high speed flight. I have run it with the cowl on and also with it off and don't see any obvious difference with temperature.
It runs a prop that it can turn with ease, a cut down 7x7 model that has had some thickness removed from the blades...this helps prevent runaway heat issues. The other things that help keep it cool is having the right compression/nitro combo [in this case no nitro] and I'm running straight castor, 25% total.
It sounds extreme, but I believe the extra oil has helped keep this engine from very much wear.
It's not my 1st Nelson .40 engine, but it's my most long lasting one.