"nrp" wrote:

My suggestion - Could just be lower internal friction due to oil
viscosity, or even the engine simply breaking in.

The engine is well broken in. 300+ hrs. since a top overhaul.

I'd almost be more
concerned about why it always stopped horizontally, as at least most
broken-in 4 cylinder engines stop with the prop at 45 degrees (10:30).

Really? This seems to vary among the O-320 and O-360 engined aircraft I see
on the ramp. I'll do a more careful survey next time I'm out there.

First verify that the mags actually do indeed shut off, then kill the
engine with the mixture, and do a hand prop to see if all cylinders
feel the same. Only if there is a noticeable difference, get a
compression check.

Did that. They feel the same.

--
Dan
C172RG at BFM