Considering a conforming engine set, valve overlap can be disregarded.
In a race engine set up, all tricks are available, but a certified aero engine should be used with a very limited spark timing variation, and only one cam set up.
Unburned fuel and Carbon Monoxide in the exhaust should be limited for as much as possible.
Fly lean and green.
In the context of this thread EGT’s in a piston engine are therefore totally meaningless as an absolute value.
CHT’s are very meaningful as an absolute value.
You are correct regarding Lycoming’s leaning “instructions”. BTW -They are not instructions, of course. Only a recommendation by Lycoming.
As an engine manufacturer they can’t give instructions how to fly an aircraft whatsoever.
Anyway, I have checked and the old document has been recently edited (once again).
They have removed the bit regarding “LOP is not recommended”.
I know the boss of Lycoming has stated LOP works, it is just the user who does usually not understand proper procedure and goes too rich when LOP.
(found this unanswered post when doing some admin)
What has been your experience with these power settings in terms of engine longevity, over the years?
Peak EGT seems to have no bad effect whatsoever on the IO540 engine. Mine was stripped down a total of 3 times during its 2000hrs life (1x for shock load, 1x for the crankshaft swap, 1x finally) and was always clean.
BTW I merged some general engine management threads into this one.