wrote in message
oups.com...
On Sep 8, 10:52 am, Newps wrote:
Matt Barrow wrote:

real simple with a wet top end and tight valves. a clapped-out R-985
will read 80/80 right up to the point when it reads 0/80 instead.

Kinda hard to have a wet top end in a Continental 520/550, isn't it?

uh, no.

Okay...so I'm misunderstanding a wet top end. Still, you inferred the
accusation that Newps was faking his compression levels, so put up or
shut
up.

I'm assuming a wet top end is an engine tested that just got done
flying. My engine was cold, the mechanic towed it over to his side of
the T hangar building that morning so all cylinders were 60 degrees F

Some guys will squirt oil into the cylinders to make the rings
seal. It's not a realistic way of testing compression, but can serve
to separate leaking rings from a cracked piston, maybe. Auto mechanics
sometimes use the trick to determine whether the loss is past the
rings or one of the valves or maybe the head gasket. With aircraft
engines, the differential test allows the mechanic to listen to the
crankcase filler for leaking rings, the exhaust for bad exhaust
valves, and the intake for a leaking intake valve. Running soapy water
over the head will find cracks in it. Older Lycs had problems with the
head cracking between the bottom sparkplug hole and the exhaust valve
seat.
Testing the compression with the engine really hot determines
the actual operating condition. The clearances between the piston and
cylinder are at a minimum and the ring gaps are smaller. We always get
worse readings if we do them cold.


Thanks, Dan!

If Toecutter had been this through in his response, we might have precluded
that ****ing contest in the other, parallel thread.