Have you ever read Lycoming's recommendations for leaning their engines?
The engine runs as cool at 25 degrees lean of peak as it will 25 degrees
rich of peak. It isn't as smooth, and it has that lean "bark", but it
doesn't hurt the engine if the power setting is below 75 percent. The
engine runs cleaner.

We had a customer once who was scared to lean his engine correctly. He
leaned just enough to keep the engine smooth at altitude. One day he took
off from a mountaintop airport and had two intake valves seize. Luckily,
there was another airport in the valley below, so the airframe survived
fine. But his fear of leaning sure made a mess of that Lycoming.


"Ron Webb" wrote in message
...


Yea, I've heard of it. You won't catch me, or anyone I know trying it for
very long. Experimenting on a $15K IO360
is not something I am comfortable with.


Never heard of "agressive leaning" of air cooled aircraft engines?
Below peak power it is very viable

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