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On Sun, 08 Jan 2006 05:02:33 GMT, George Patterson
wrote:

In the absence of some catastrophe, such as a bent pushrod, this is
generally
caused by not flying enough. The layer of hardened steel on a camshaft is
fairly
thin. Let the plane sit long enough, and rust will form. When the engine
starts
again, the rust is worn away, making the thin layer of hardened steel
thinner.
The worst wear points, of course, are the tips of the lobes. Once the
hardened
steel wears through, the softer steel underneath goes pretty rapidly.

The automotive world tried out roller lifters a long time ago. They
would work fine in aircraft engines too. I've heard that some of the
engines built for the homebuilt market can and do incorporate roller
lifters. I even thought I read that at least one company was
intending to certify such an engine.

Corky Scott

It is not uncommon to see roller rockers on round engines.