"John R. Copeland" wrote in message
.. .
Doug's advice about never leaning above a safe temperature
is well advised, and it's exactly what I've followed for 25 years.
In fact, I found that leaning to RAM's recommended 1550F
still results in a little exhaust-system distortion, and I've held to
1525F max for the last ten years or so, with better results.

I believe their recommendation at 75% power is 100 degrees rich of "peak",
not 100 degrees rich of 1650 degrees. Most engines will peak at a
temperature less than 1650 degrees.

Allen