sticky valve or

Dick wrote:
snip
Light Plane Maintenance book references "hand proping before first
start of
day to find 'flat' cylinder". Not sure I can identify a rapid falloff
in
turning resistance (books definition).

I think you can. It should be pretty straight forward. As you
rotate the prop you can feel the resistance from each cylinder on the
compression stroke. If you hit a cyl. with a stuck valve, you'll
notice the difference in resistance right away. If it's quiet, you
should also hear hissing at the exhaust pipe if it's an exhaust valve.


John Galban=====N4BQ (PA28-180)

Could you describe the "wobble test"? Not familiar with the term.
Thans, Dick
"Robert M. Gary" wrote in message
oups.com...
I would do a wobble test. If you do have a slight stick to the valve it
will get worse and at some point could cause in flight problems. A
wobble test should set your mind at ease.

Two of us tried the "armstrong method" (rotating by hand) yesterday and both
thought we got very slightly lower resistance, but on different cylinders on
opposite sides of the engine. Him #1 and me #2 &#4..

Decided to do a "differential test" with the engine cold, rather than warmed
up. Our thought being that any matter between seat and valve would
indicate a lower reading.

Observed 78/80 on three and 77/80 on the fourth. For last 5 years the
readings have been in the 76-78 over 80 psi range.

Don't know if it matters in my case, but realize now that I've never
listened for any leaks.

My helper did mention that he thought the leakdown period should be about 5
minutes instead of just holding 80 psi long enough to observe where
indicator stops...

Thanks, Dick

ps Glad to hear that 11-1200 rpm hesitation is normal.

On Tue, 24 May 2005 11:03:11 GMT, "Dick" wrote:

Could you describe the "wobble test"? Not familiar with the term.
Thans, Dick
"Robert M. Gary" wrote in message
roups.com...
I would do a wobble test. If you do have a slight stick to the valve it
will get worse and at some point could cause in flight problems. A
wobble test should set your mind at ease.

It literally means removing the rocker arm and valve spring, grabbing
the valve stem and seeing if you can wobble it back and forth. If you
can it means the valve guide is worn.

The valve guide has to hold the valve in it's cylinder without
wobbling because if it's wobbling it isn't seating on the valve seat.
If it isn't seating on the valve seat properly, it's leaking. If it's
leaking, it's either burned or about to be burned (if we're talking
about exhaust valves).

See: http://egaa.home.mindspring.com/engine1.htm for an extremely
comprehensive look at the issue of valve guide wear in parallel valve
Lycoming engines.

Corky Scott

Here are some interesting pictures of what can happen when the engine
is unhappy...

http://carneyaviation.com/enginefire/


-Robert

"Robert M. Gary" wrote in message
oups.com...
Here are some interesting pictures of what can happen when the engine
is unhappy...

http://carneyaviation.com/enginefire/

Ahh, that's not so bad! Find all the pieces, and weld them back together.
Try to get to that TBO, that you got cheated from! ;-)
--
Jim in NC

They call that the "Continental cough"...My A-65 doesn't do it, my dad's
C-85 doesn't do it, but my old C-85 on my Chief did. Don't think that
is worth worrying about...

Scott
http://corbenflyer.tripod.com


Dick wrote:

Two of us tried the "armstrong method" (rotating by hand) yesterday and both
thought we got very slightly lower resistance, but on different cylinders on
opposite sides of the engine. Him #1 and me #2 &#4..

Decided to do a "differential test" with the engine cold, rather than warmed
up. Our thought being that any matter between seat and valve would
indicate a lower reading.

Observed 78/80 on three and 77/80 on the fourth. For last 5 years the
readings have been in the 76-78 over 80 psi range.

Don't know if it matters in my case, but realize now that I've never
listened for any leaks.

My helper did mention that he thought the leakdown period should be about 5
minutes instead of just holding 80 psi long enough to observe where
indicator stops...

Thanks, Dick

ps Glad to hear that 11-1200 rpm hesitation is normal.

"Deborah McFarland" wrote:

Dick,

The hesitation at 1100-1200 rpms in a C-85 is normal. I have it on mine (275
smh with 0-200 conversion stc) as do most of my Luscombe brethren with the
C-85.

I recently had an exhaust valve to stick in flight. It was interesting to
say the least, and in reaction to that experience I would like to pursue a
glider rating ;-).

My valve in my 275 hour ECI cylinder was stuck but good. My engine guy
reamed it out a little as he thought the clearance was a little tight. MMO
is now part of my regular maintenance routine.


Deb


Hey Debby, it's been far too long. Does the gang still get together
Saturday afternoons at JZP? Gotta catch up.

David O

Wow - what mayhem! I hope you'll post the prognostication on what
failed first. Congrats on a safe landing.

From your pix it could look like the con rod failed, but were either of
the the rod bolts found? There were some bogus bolts some years back
now removed by an AD and a lot of bogus bolt publicity. I understand
the normal spec for Lycoming rod bolts does not involve tightening only
to a torque, but rather ends with a turn-of-the-wrench method. If the
bolt strength happens to be low, the usual torque-only procedure won't
detect it unless the mechanic is very experienced and suspicious.

Be careful that failed parts don't mysteriously get lost by those that
might have some resposnibility for this mechanical carnage.