In article ,
"O. Sami Saydjari" wrote:

OK. I have a basic question. Why is running an engine at peak
temperature (as in Rich-of-Peak operation) not good for the engine?

There is nothing wrong with running an engine at peak EGT if it is happy
to run there. That's where I run mine, in accordance with my POH.


In
the scheme of things 50-100 degress cooler than peak temperature (where
many folks recommend the engine be run) does not seem significantly
lower in temperature than the peak temperature. It would seem if the
engine parts can stand Peak-100 degrees, they would be able to stand
peak. What am I missing? (Oh, and I have read Deakin's articles on
AVWEB, and still have this question).

When you read Deakin's articles, you are not too subtly encouraged to
take away the belief that running 50-100 ROP is actually worse for the
engine than running either much richer or much cooler. He provides
graphs and text to explain why.

The incorrect assumption explicit in your question suggests that you
have misunderstood something fairly fundamental about what you read.
You should go back and look at the graphs of EGT, CHT, HP, and peak
pressure, plotted against fuel mixture. Convince yourself of where CHT
and peak pressure are at a maximum, and see where that lines up against
EGT. It should be around 50-100 ROP. Note how as EGT continues to
increase, CHT and peak pressure (the real enemies) actually decrease.

Also look at your aircraft panel. Note that CHT has a redline. Note
that EGT (most probably) has no redline. Your engine is designed to
tolerate maximum EGT. It is not designed to tolerate arbitrarily high
CHT. You manage EGT to control CHT.