“Exhaust valve troubles won't go away because the cooling gradient between the valve and the head is so low compared to liquid cooled engines. The basic laws of physics just don't change. The constraints they impose limit solutions.”

The best solution to exhaust valve cooling is 2 Exhaust valves per cylinder.  Heat transfers more quickly with a shorter distance to travel.  Honda used a 4 valve head in the prototype aircraft engines Continental was testing for them a few years ago, most modern motorcycle engines use 2 Exhaust valves.  If the economic and liability issues were solved, I’ll bet we would see them in Continentals and Lycomings for better reliability and performance.

Steve Colwell  Legacy