Speed is irelavant if the burn is contained in the chamber as the valve is
closed. Same as the inlet. It made of a different material but as it's no open
to the gas flow it dose not get effected.
So at what temp lean of peak will this combustion not be contained within the cylinder. The reduction in mixture burn rate would be progressive so at what temp will it start to erode the exhaust valve. Will this happen any temp leaner than best power or leaner than peak or leaner again say 50 LOP.
You have made a statement that the slower mixture burn at LOP makes it combust beyond the valve opening but the mixture with ROP the slower burn does not exit?
I have owned and managed piston aircraft in the past but not now, maybe in the future.