Gary Casey Wrote:

"And since higher temperatures reduce strength and creep qualities it can be
expected that running at higher temps and pressures will reduce engine
life."

Well, this statement also deserves a "maybe yes and maybe no" as well.

As regards to temperature, most engines, at least the big Continentals for
sure, are designed to operate at an optimum (relatively high) cylinder
temperature and as a result, are designed with cylinder choke (the upper
part of the cylinders are tapered to a slightly smaller diameter than the
lower). The idea is that the choked region of the cylinders expand due to
temperature (measured indirectly as CHT) enough for the cylinder walls to be
close to parallel once heated to operating temperatures, e.g., once the
engine is making a lot of power.

If you consider high temperatures a bad thing and run your CHT's too low,
the cylinders do not expand properly, as designed, and in short order the
choke is scrubbed out by the piston rings. Ring sealing at the most critical
part of piston travel (at, or close to the top of travel, where the pressure
is highest) suffers as heat transfer through the rings decreases and blow-by
increases. Compression drops and your jugs need topping, as a minimum.

Additionally, the high combustion pressures developed in a jug with good
compression gets behind the compression ring(s), pressing it (them) outward
against the cylindrer wall, and aids in providing a good ring to cylinder
wall seal.

Granted, excessive (over red-line) cylinder temps, and the extreme pressures
resulting from such maladies as detonation certainly will drastically
shorten engine life (sometimes to just minutes). But in a non-detonation
environment, choked cylinders operated at temperatures that are too low will
also severely shorten their service life.

Dan Schaefer