Paul Folbrecht wrote:

As for sitting for a long period - it doesn't appear to have done that.
Just below-average usage over the last two decades.

Hi Paul,

I bought a high time engine, below average used 1976 Beech Sundowner.
Plane had 1940 total time on the air frame and engine. Compressions
were high (78 / 79 on all cylinders), oil showed no metal, thought
everything was fine.

I bought it knowing overhaul was in my future. I figured to fly it and
get the hard learning curve on the engine (I was flying Cessnas). I
just didn't know how soon my overhaul was to be. At 2010, a cylinder
ate an exhaust valve in flight. Got the cylinder replaced, flew another
10 hours, couldn't get the engine to pass mag check, taxied back, and
got the overhaul. Reason for mag check failure was another cylinder,
both plugs were getting "wet".

I think I learned most, that you can't fully make a decision on good
compressions. To me, it's almost like too much emphasis is being placed
on compressions. The A&P figured that the exhaust valve probably rusted
/ corroded and failed due to the lack of usage. So, what's happening on
the bottom side of the engine is equally important.

So, knowing an under used plane is actually worse then a plane that has
been flown frequently, choose the frequently flown plane. My first
annual was just short of $4000.00 to get all the points that had grease,
lubrication back up to speed. My plane was only run 10 hours in the
prior two years before my purchase. From what I gather, some of this
time was ground runup time, so it probably was flown less!

The positive thing about this, now that I had the major overhaul, I know
how the engine is being run as I got to break in the engine. I ran it
full throttle, full rich for the first 25 hours.

I fly no less then once a week, unless of course I am out of town.

Allen