"gman" wrote in message
ups.com...

The consensus around here is that as long as the engines are blessed by
the mechanics and checked for compression, one can exceed the
recommended TBO sometimes by a factor of 2x.

The Oct '06 edition of "Light Plane Maintenance" fielded
a question on exceeding TBO with a Lycoming O-320
in a Cessna 172 (you didn't say what engine you have).
The engine burns 1qt/8 hours and the compressions are
all in the low 70s. The owner recently did a valve wobble
check.

Biggest concern: exhaust valve break up, which apparently
nearly always happens in flight, but which is usually
preceded by said valve getting burnt, then getting hot, and
then failing.

Recommendation: Continue flying until engine gives a
reason for overhaul. Increase monitoring, especially by
doing frequent compression checks (25 hours) and attention
to oil (filter/screen + oil analysis). Compression check
verifies both cylinder & valves not seating properly. Investigate
if any cylinder showing compression in the low 60s.