A Lieberman wrote in message ...
Dan Thomas wrote:

The Type Certificate Data Sheets will give minimum and maximum
static full-throttle RPMs for that engine/prop combination in that
airplane, and if there is valve train wear the RPM will be out of the
range. This isn't rocket science. If the crank is eating its way into
something, there'll be metal in the filter. That's simple enough, too.
If the oil pressure is well into the green, and doesn't drop to zero
at idle when hot, the bearings are OK. If the compressions are as high
as he's indicated, there isn't much wrong with the top end of the
engine, other than perhaps corroded valve stems.
Lycomings have been known to swallow valves when the head broke
off the stem because of corrosion pitting in engines that have been
run for short periods and left to sit. Similarly, the crankshafts in
these engines build up water/oil sludge in the crank nose (unless it's
driving a constant-speed prop) and this causes dangerous corrosion
that can result in propeller departure.
Lycomings run regularly on long flights have reached 4000 hours
without overhauls.
Tell me what airplane it's in and I'll look up the prop RPM range
for you.

Thanks for answering Dan,

It makes more sense what you say about metal in the oil, as I was going
to post how would I know what is happening "below the top" without an
overhaul.

The engine is in a BE 23 (Beech Sundowner). I bought the plane for
$38,000 knowing a major overhaul is in my short future, but wanted to
get my learning curve behind me in this engine before overhualing it.

Hokay. For the B-23, with Lycoming O-360-A2G, and with either
Sensenich prop number M76EMMS-0-60 or 76EM8S5-0-60, the full-throttle
static RPM should be not over 2350, not under 2250.
You'll want to make sure of the engine and prop models, to be sure
there hasn't been some STCd change in the past. The tech logs will
have this dope. The tach should be checked for accuracy, too; they're
often 100 RPM low. Most current tachs (in singles) are the magnetic
type, and the magnet weakens with time. Here in Canada we have to
check them yearly, and they can't be off by more than 4% of the
midrange cruise RPM.
Dan