Sticking Lycoming O-360 valve again?

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 *
************************************************** ***********************

If you are using auto gas in that engine there is no way of knowing
what may be causing your valve problem. Auto gas is not refined and
adultered to any specific standard, certainly not to meet av gas
requirements. I have worked as an engineer in the petrochemical
industry and can assure you that auto gas may have any number of
additives that would cause valve problems in an av engine.

BTW -

How often do you change oil? Confirm you have a full flow filter (it
reads like you do). Does your oil filter have gray (lead) sludge in
it?

What fraction of the time since you got the engine has been 100LL vs
autofuel? I assume the autofuel has to be 91 octane autofuel to handle
your compression?

Have you ever tried to do a mag check at cruise? (i. e. could one mag
be somehow intermittent at temperature?).

Be sure to check inside the rocker covers to see if the rocker shafts
are wearing on the cover sides. I found one (but only one) in my 172M
(1700 TT over 31 years) that was worn substantially. Later shafts have
a nylon thrust boss.

You gotta post what you find. THX

Whatever you do - don't use abrasives of any sort on bronze. If you
do, it may charge the bronze with abrasive material making it into a
lap. Be careful with the reamer too.

: How often do you change oil? Confirm you have a full flow filter (it
: reads like you do). Does your oil filter have gray (lead) sludge in
: it?
Full flow filter, 50 hours, Aeroshell 80/100 depending on winter/summer. No
lead sludge in the filter, and very tiny (i.e. normal) amount of metal and carbon in
the filter and its element.

: What fraction of the time since you got the engine has been 100LL vs
: autofuel? I assume the autofuel has to be 91 octane autofuel to handle
: your compression?

93 A.K.I autofuel is used for local cruise. Generally at least 25% 100LL on
the takeoff tank. I'd say in the 3-400 hours since we've run it, probably about 60%
on autofuel.

: Have you ever tried to do a mag check at cruise? (i. e. could one mag
: be somehow intermittent at temperature?).

Done in-cruise mag checks. All fine. I generally check it along with my
leaning to verify no rough on just one mag.

: Be sure to check inside the rocker covers to see if the rocker shafts
: are wearing on the cover sides. I found one (but only one) in my 172M
: (1700 TT over 31 years) that was worn substantially. Later shafts have
: a nylon thrust boss.

Will look when I get them off. Probably take a look on Saturday.

: You gotta post what you find. THX

Will do.
-Cory

--

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

I just remembered a local chromed C-85 engine that would "sag" on
takeoff after an overhaul. It was supposedly traced to inadequate ring
gap. I find it hard to believe in your case though after your amount of
time since OH.

You might check the carb floatbowl fuel level with the clear flex
standpipe connected into the carb drain port method. I'm otherwise
outta ideas.....