Sticking Lycoming O-360 valve again?

Have you done the "wobble check" on the valves?

wrote:
Hey all. Question about my Cherokee's O-360. When we first got it about 3.5
years ago, it was very low hours SOH, but almost 10 years. We had some sticking
valves and bad oil consumption, so sent the jugs out to have the IRAN. At that time,
in addition to the the IRAN, a few rusted valve springs were replaced with servicable
ones by Triad Aviation. Broke in and settled on about 1qt/8 hours on chrome jugs...
good by all I've talked to. Ran fine, although the max static runup I'd ever seen was
right in the midrange.... 2350 or so. Often it was on the low end... 2275-2300.

For a little while now (6 months or so), it seems to have a bit of
"mid-morning" sickness. It starts up and runs smooth and fine. Taxis smooth, runup
good, mags fine. On the takeoff/climbout, it just doesn't "feel right." Not bad
enough to know something's amiss, just enough to look at the VSI and say, "Hrm... I
should be getting a little better climb than this." Usually within a minute or two of
liftoff, it picks back up and I get an additionall 200 fpm or so. The usual
in-flight diagnostics reveal nothing.... mixture, carb heat, mags, fuel pressure,
CHT/EGT, etc. Runs smooth on either mag (with reduced power)... on high DA days
leaning it a bit might be necessary, etc.

Sounds a lot like a sticking valve, but I think I've done everything that can
be done to prevent that. Baffling is in great shape. I never allow climb CHT over
400 or cruise over 380... and that's on the *spark-plug* CHT probes... They've been
verified reading at 50-60 degrees hotter than the bayonet-style that Lycoming uses, so
the CHT is actually 325-350 max. I generally cruise no higher than 65% and lean to
about peak EGT as per Piper/Lycoming recommendations, so there shouldn't be much for
rich combustion byproduct buildup.

Other suggestions? I'm figuring to pull off the rocker-box covers, push on
the valves, and see if I can feel friction in any of them.

Thanks,
-Cory

Otis Winslow wrote:
: Have you done the "wobble check" on the valves?

Not since the shop did the IRAN 3 years ago. It was the relatively close-by
Triad (Lycoming certified repair center), so I'd assume that was part of the
inspection.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

Take a good look (or have someone take a good look) at your exhaust system. Our
Archer seemed to have lost power and kept getting worse. Everything seemed normal,
except I'd guess it was lacking 20 - 30 HP, but was using fuel at almost the
'normal' rate. We finally looked at the exhaust and found that it was coming apart
internally and some of the loose pieces were effectively blocking the exhaust flow.
Since these pieces were loose and moving around, the effect was worse at some
times than others. Had the exhaust system rebuilt and it performs as good as ever...

Mike Pvt/IFR PA28-181 at RYY


wrote:
Hey all. Question about my Cherokee's O-360. When we first got it about 3.5
years ago, it was very low hours SOH, but almost 10 years. We had some sticking
valves and bad oil consumption, so sent the jugs out to have the IRAN. At that time,
in addition to the the IRAN, a few rusted valve springs were replaced with servicable
ones by Triad Aviation. Broke in and settled on about 1qt/8 hours on chrome jugs...
good by all I've talked to. Ran fine, although the max static runup I'd ever seen was
right in the midrange.... 2350 or so. Often it was on the low end... 2275-2300.

For a little while now (6 months or so), it seems to have a bit of
"mid-morning" sickness. It starts up and runs smooth and fine. Taxis smooth, runup
good, mags fine. On the takeoff/climbout, it just doesn't "feel right." Not bad
enough to know something's amiss, just enough to look at the VSI and say, "Hrm... I
should be getting a little better climb than this." Usually within a minute or two of
liftoff, it picks back up and I get an additionall 200 fpm or so. The usual
in-flight diagnostics reveal nothing.... mixture, carb heat, mags, fuel pressure,
CHT/EGT, etc. Runs smooth on either mag (with reduced power)... on high DA days
leaning it a bit might be necessary, etc.

Sounds a lot like a sticking valve, but I think I've done everything that can
be done to prevent that. Baffling is in great shape. I never allow climb CHT over
400 or cruise over 380... and that's on the *spark-plug* CHT probes... They've been
verified reading at 50-60 degrees hotter than the bayonet-style that Lycoming uses, so
the CHT is actually 325-350 max. I generally cruise no higher than 65% and lean to
about peak EGT as per Piper/Lycoming recommendations, so there shouldn't be much for
rich combustion byproduct buildup.

Other suggestions? I'm figuring to pull off the rocker-box covers, push on
the valves, and see if I can feel friction in any of them.

Thanks,
-Cory

Mike H wrote:
: Take a good look (or have someone take a good look) at your exhaust system. Our
: Archer seemed to have lost power and kept getting worse. Everything seemed normal,
: except I'd guess it was lacking 20 - 30 HP, but was using fuel at almost the
: 'normal' rate. We finally looked at the exhaust and found that it was coming apart
: internally and some of the loose pieces were effectively blocking the exhaust flow.
: Since these pieces were loose and moving around, the effect was worse at some
: times than others. Had the exhaust system rebuilt and it performs as good as ever...

: Mike Pvt/IFR PA28-181 at RYY

There's an AD against the exhaust IIRC. I know we've checked it in the past, but it has
been awhile.... worth looking into. We very well may have it off if we're messing with the
valves anyway...

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

Is it rough running at all? or does it feel just weak in general?

Does the EGT behave normally? Your CHTs seem a little high even though
they are sparkplug versions.

Do you by chance have alcohol in your autofuel?

Do a proctology exam on the muffler.

Hmmmm.

nrp wrote:
: Is it rough running at all? or does it feel just weak in general?

Not really. Possibly very slight, but in general just weak. It's kinda hard
to tell since the 4-banger always rocks and rolls a bit.

: Does the EGT behave normally? Your CHTs seem a little high even though
: they are sparkplug versions.
Again, it's a bit hard to tell on the EGT. I don't have an analyzer... just a
switched analog gauge. Last time I had time (i.e. in cruise) everything was
normal.... the EGT has a bit of a spread, but I chalk that up to a dissimilar air/fuel
ratio in the cylinders leaned for cruise.

As far as the CHT goes, when I first got the thing, I was worried about
bumping up against 400 all the time. I put a single bayonet probe in #3 and wired it
into the gauge on a switch. I verified that (at least on that cylinder) I read almost
75 degrees higher on the spark-plug probe vs. the bayonet in general. The bayonet
probe will read 300-325 in cruise at the same time the spark plug reads 375. Since
I've also got a multi-point Tannis heater, I seasonally remove the bayonet probe in
lieu of the heater for #3.

: Do you by chance have alcohol in your autofuel?

The current fuel in the tank is 100LL. I don't check every batch of autofuel,
but I generally check a sample every 4-6 months and I always get it from the same
station. Haven't found alcohol yet. When I first started running it I called the
distributor for the station and he says they never put alcohol in it.

: Do a proctology exam on the muffler.

"You will feel some slight discomfort..."

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

One thing - If you have a worn cam lobe, there won't be a significant
loss of power until a very substantial percentage of the lobe is worn
away. I'd think you'd see metal in the filter, too. I know of an
O-320 H engine that had a pair of intake valves that hardly moved & the
thing did seem "kinda weak", but still ran fairly smooth.

Sounds like you've covered a lot of the bases.

: Other suggestions? I'm figuring to pull off the rocker-box covers, push on
: the valves, and see if I can feel friction in any of them.

Still haven't done this (probably won't have time until the weekend). I am
trying to amass some parts to facilitate the quickie valve job. I've talked with my
mechanic and gotten ahold of SI1425 (i.e. "rope trick") and SSP1776. They *appear* to
specify the valve guide stem of 0.4985" for my O-360. SI1425 seems to give three
different reamer sizes for the nominal 1/2" size. I assume one would want to go with
the smallest (0.4985-0.4995) if possible, and only move up to the larger
(0.4995-0.5005, 0.5000-0.5010) if necessary.

I've also read that it's pretty easy to screw up the guides with the reamer,
which I would tend to agree with. They're *made* for cutting, and all I'd be trying
to do is get the carbon off. I've seen people recommend one of these:
http://tinyurl.com/bx8l3
... seems like a good way to have an adjustable, non-cutting type way to
scrape off carbon in the valve guide without taking off bronze.

I will of course be doing this with my mechanic, but I just figured I'd ask
the collective wisdom of the group on this. Good way to go?

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

I have not used the flexible cutter you listed in the URL... I have
reamed a number of valve guides over the years... My experience has
been that you will find a combination of carbon / lead salt deposits
and slight warpage (sometimes not so 'slight')... So, the straight
reamer at the nominal 0.4985" size will do the best job... It will
remove deposits and ream out the tight spots inside the bore...
Your mechanic knows best, but my suggestion is to do it by hand with a
Tee handle - and lots of muscle... The thought of using a drill motor
may be attractive, but in less than experienced hands it can wreck the
guide and then you will have to have the jug pulled and repaired...

There is still nothing stopping you from first putting solvent down the
guide bores, fresh oil, AVBLEND + MMO, and flying it... Less work and
cost than reaming the guides and doesn't do anything that can't be
undone...
Local FBO and I did this to his rental Skyhawk recently when it
suddenly stuck an exhaust valve and almost cost him a a 100 hour block
rental from customer who needed to scout a number of factory sites
across the southland over a 4 week time period, leaving the very next
morning... This was big bucks down the drain if the airplane couldn't
go the next morning...
A large spray can of WD-40 (only thing we had on hand that night) and a
quart of MMO in the oil saved him a valve job... The ol hawk came back
still humming along... Old chinese adage, "Softly, softly, catchee
monkey"..

denny

Denny wrote:
: I have not used the flexible cutter you listed in the URL... I have
: reamed a number of valve guides over the years... My experience has
: been that you will find a combination of carbon / lead salt deposits
: and slight warpage (sometimes not so 'slight')... So, the straight
: reamer at the nominal 0.4985" size will do the best job... It will
: remove deposits and ream out the tight spots inside the bore...
: Your mechanic knows best, but my suggestion is to do it by hand with a
: Tee handle - and lots of muscle... The thought of using a drill motor
: may be attractive, but in less than experienced hands it can wreck the
: guide and then you will have to have the jug pulled and repaired...

Good to know. I will try to locate that sized reamer. I hope I can get the
stem out the bottom plug hole to clean it if it's gunked up.

: There is still nothing stopping you from first putting solvent down the
: guide bores, fresh oil, AVBLEND + MMO, and flying it... Less work and
: cost than reaming the guides and doesn't do anything that can't be
: undone...
: Local FBO and I did this to his rental Skyhawk recently when it
: suddenly stuck an exhaust valve and almost cost him a a 100 hour block
: rental from customer who needed to scout a number of factory sites
: across the southland over a 4 week time period, leaving the very next
: morning... This was big bucks down the drain if the airplane couldn't
: go the next morning...
: A large spray can of WD-40 (only thing we had on hand that night) and a
: quart of MMO in the oil saved him a valve job... The ol hawk came back
: still humming along... Old chinese adage, "Softly, softly, catchee
: monkey"..

My only thought on that is that it's an intermittent problem. Doesn't happen
repeatably, and when it does it happens to be right when there's no negotiation
allowed.... right after takeoff. Aside from a day/weekend worth of work, I'm thinking
that taking it out and cleaning it is the right way. There seems to be more than the
usual amount of OWT/circumstantial evidence supporting useage of MMO as preventative
measure. I'm generally skeptical of such snake oil, but I could see how it's possible
to help some.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************