Sticking Lycoming O-360 valve again?

Stop using MV oil and only use Shell single weight and your valve
problems will go away.

darthpup wrote:
: Stop using MV oil and only use Shell single weight and your valve
: problems will go away.

Bzzzt....

Aeroshell 100 or 80 AD since the Aeroshell mineral oil for 25 hours on
breakin.



--

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

wrote:
darthpup wrote:
: Stop using MV oil and only use Shell single weight and your valve
: problems will go away.

Aeroshell 100 or 80 AD since the Aeroshell mineral oil for 25 hours on
breakin.

Well, there you are. Switch to 15W50 and your problems will go away. :-)

George Patterson
Coffee is only a way of stealing time that should by rights belong to
your slightly older self.

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

George Patterson wrote:
: Well, there you are. Switch to 15W50 and your problems will go away. :-)

Why didn't *I* think of that? ;-)
-Cory
--

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

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.

Cory,
26" at 3500 seems a tad low.. Maybe others can chime in on this...
Cam problems can result in low manifold pressure, so the plot
thickens...

Also in case I am misreading, static RPM check R to L is done at full
throttle, not at 1800, or whatever you normally use for mag drop...
And, it will verify that the impulse pin is releasing properly if they
are similar...

Seems like you have a good grasp on engines so I don't want to keep
throwing out picky stuff... But, once you have the cowl off I would
still verify that the butterfly is not loose on the shaft and that it
opens fully...

You don't happen to have a Precise Flight vacuum system, do you?
grasping at straws A fine puzzle we have here... Looks like
measuring the cam is next...

Cheers ... denny

Denny wrote:
: Cory,
: 26" at 3500 seems a tad low.. Maybe others can chime in on this...
: Cam problems can result in low manifold pressure, so the plot
: thickens...

I don't remember the altimeter setting that night, but it was pretty clear
that day. I'd think it was about 30"... at 1"/1000', that'd be 26.5" theoretical max.
The MP is measured at the intake port on #3 cylinder... losing 1/2" through the
induction system is normal AIUI.

: Also in case I am misreading, static RPM check R to L is done at full
: throttle, not at 1800, or whatever you normally use for mag drop...
: And, it will verify that the impulse pin is releasing properly if they
: are similar...
Never done a full-throttle mag check with anything in particular I was search
for other than max RPM. What would a full-throttle mag drop tell you? I don't know
of anywhere the allowable spec for that is given. The POH specifies at runup RPM, and
the TCDS specifies min/max RPM for static... but that's for both mags and mixture
leanded for DA.

: Seems like you have a good grasp on engines so I don't want to keep
: throwing out picky stuff... But, once you have the cowl off I would
: still verify that the butterfly is not loose on the shaft and that it
: opens fully...

Will do once I get the cowling off.

: You don't happen to have a Precise Flight vacuum system, do you?
: grasping at straws A fine puzzle we have here... Looks like
: measuring the cam is next...

I was thinking measuring the friction on the valves is probably next. With
the covers off the cam measurement may come in. I've talked with my mechanic and he's
got a jig and dial indicator rigged up to measure it. Too bad I *ALSO* need to fix
the ring gear. I won't be able to spin it up fast to get good lifter inflation.
Maybe I can hand-turn it slow enough to keep no inflation?

Thanks
-Cory

--

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

: You don't happen to have a Precise Flight vacuum system, do you?
: grasping at straws

Ooops. Nope... plain O-360-A4A.

--

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