Prop position

wrote:

I'm pretty sure where the prop stops doesn't measure anything.
How do you know it stopped in the same place "horizontally"
each time?

Because I've been watching it carefully for 3 years.

A prop that stops in an unusual position can indicate a cylinder with poor
compression, as I discovered when I had cylinder trouble 3 years ago.

There are at least two possibilities.

Why would the prop stop in a preferential position anyway?
Seems like it would be on any one of the 4 compression strokes.

Becaues of the crankshaft geometry of the horizonally-opposed Lyc. O-360,
the prop will stop in the same compass position every time as it bounces
back from the last TDC.

I'm also convinced that even the differential compression
check doesn't show what you really want to know.
The rings are AC coupled, tho less so in the Lycomings.

?

So I'd guess one would need something worse to worry
about. Maybe price of gas or user fees!

No. Something has changed, and that's something to worry about.

--
Dan
C172RG at BFM

Update:

I went to the airport first thing this morning to turn the prop with the
engine cold. As before, I felt good compression at each cylinder, and the
prop stopped at 02:30/04:30.

So I ran the engine for 3-4 minutes, just to get the oil a little warm, and
shut it down. Voila': the prop stopped at its usual 09:00/03:00 position.

I don't know WTF to think, now.

Wait a minute, yes I do: I think I'll have a couple of Coronas and forget
about it..

--
Dan
C-172RG at BFM

Dan -

Does the engine always feel tight only when hot? If so, as a
precaution, do an oil analysis next change or next time the cowl is
off. Don't waste money on a more formal compression test.

You don't have top end trouble, but you just might have a problem at
the bottom end.

"nrp" wrote in message
Dan -

Does the engine always feel tight only when hot?

No.

If so, as a
precaution, do an oil analysis next change or next time the cowl is
off. Don't waste money on a more formal compression test.

You don't have top end trouble, but you just might have a problem at
the bottom end.

Like what?

You don't have top end trouble, but you just might have a problem at
the bottom end.



I mentioned that to my wife a few days back... and got slapped...

Like what? Possibly, and I want to emphasize just possibly - a shelled
out camshaft system contaminating the crank bearings such that they
shrink onto the crankshaft on cooldown. An oil filter check (assuming
there is one) would also show if something is shelling out. Maybe even
just looking critically at the oil on the dipstick would show aluminum
or steel "paint" immediately after a shutdown.