Scudrunners

That binding you're feeling when the engine
is hot needs looking at.

Engine total time since new?
Time since overhaul?
Years since overhaul?

I would check the basics:  pull the plugs,
look at them.  Anything weird?  Take a
picture, in the tray.

Check compressions - cold and hot.  Check
for metal in the oil screen/filter.

Do you have a 6 cyl CHT/EGT?  What are
the temps like?

Might be worth pinging Mike Busch.  He
can actually diagnose.

@ 1500 SMOH
Always flown near 100 hrs / year.  150 hrs / year since I've had it.
going in for oil change soon. (Like this week)  Done oil analysis regularly. Nothing, on past changes. 
Power, CHTS, EGTS, normal. (6 cylinder probes).
Mag checks normal. 
Starts normal.
Last annual compressions great. Goes in one month for annual
Maybe plugs will pull them.

??? 

For a stuck valve / compression should be a clear EGT indication. (A real drop per the JPI manual) Will check on the ground.  Didn't notice that.

[quote]1500 SMOH[/quote]

Lycoming says to check the exhaust valves
every 500 hrs (400 rotary wing, oddly).  Do
you see any morning sickness?  Rough running
at startup which clears after a bit?

If it were my engine, I would do the rope
trick simply because of the time in service -
takes me a day or two, and doesn't cost
anything.  At the end, I would know that
the exhaust valves weren't sticking, and
the engine will run smoother.

Your AME will probably charge you thousands
of dollars to do it, if he even knows how, though,
so I'm not sure it's your best first choice or not.

Most AME's won't even do the rope trick.  They
will tell you to pull all six jugs and top them,
which will probably cost you $15,000 or so.

Talk to Mike Busch.  He and his staff make
a living doing this.  Your binding worries me.

EDIT -- one cheap thing to do, is to pop the
valve covers.  Hell, just pop one - I might
suggest the right rear, or the left front. You
can learn a lot about an engine by peeking
at the top of the cylinder.

If it's clean and shiny metal in there, no rust
or carbon, that's a good sign.

If it's corroded and black with deposits, that's
not so good.

Update.  Another long one today. Prior after a chat with my ame, pulled through prop -- forward -- 6 times --- all compressions felt good -- except one just slightly less. 

Ran up engine with another pilot, checking CHT and EGT.  # 5 is a touch low -- but same as always  -- have to look at that compression #.  Only a touch.  Smooth, no issues.  So took off and did 4 legs 6 hours. Ran like a top. 

Goes in for oil change this week, have ame pull it through too.  Not seeing any issue right now. 

Funny the worse the bush below the worse the engine sounds,  there is that effect.....

[quote] the worse the bush below the worse the engine sounds[/quote]

Heh.  I call that "water roughness" - when
you fly over water, all of a sudden you notice
that your engine isn't running perfectly smoothly.

Long before either of us were born, my father
headed out over the water in the early 50's,
flying one of four Sabres.  One of the young
pilots exclaimed over the radio, "My engine
is running rough!" Everyone else laughed.

Back to your cyl #5.  When you compression
test it, where is the air going by?  Rings?
Exhaust? Intake?  With the time on your
engine, if it's rings, one trick you can do
is to pull the jug, hone the cylinder walls
and put a new set of rings in it. 

Your young AME might resist that, though -
he will probably insist on 6 new cylinders,
which is stupid on a 1500 SMOH engine -
your cam and lifters and bearings probably
aren't exactly perfect any more.

Looks like simply dirty plugs, if anything. Lots of flying.

I'm fortunate I have, and I know I have, a legitimate, (and older) AME, who is just that, and not a salesperson.  I worry more than he does. He's perfectly happy with the engine when seeing it recently.

Goes for annual in a month and we will do compressions ect then. 

[quote]dirty plugs[/quote]

Lean the mixture on the ground, all
the time.  Lycoming also says to idle
at 1100-1200 RPM after the oil is
circulating.

You probably won't foul the plugs,
running full rich in the air, because
of the higher power setting - you
will just waste fuel, and if you had
a TCM, crack the cylinder heads in
the descent.

I lean in cruise and descent - all the
time.  In climb, once your CHT's drop
below 350F, lean also (assuming your
oil temp is below 200F)