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painless

Well Known Member
I just did my first annual on my 6A (hard to believe I have a year on it already) and came up with an issue regarding my 0320-E2D 150hp.

In checking compressions, I found that I was only getting 39/80 in #3 cylinder. I should preface this by saying that I have noticed no indication that the engine was in distress at all, this being monitored with a Rocky Mountain Micromonitor engine monitor with CHT/EGT probes in all cylinders.

Air could be heard leaking past the exhaust valve. To rule out carbon buildup that could be in the valve seat itself, I ran it up to 2000rpm, applied carbheat and leaned very aggressively for a few seconds. A helper noted crud blasting out the exhaust. Must have had some carbon buildup from doing a bunch of slow-flight on my last flight.(?)

So we checked compression on #3 and at first we were only getting 10/80 until I moved the prop just a hair and "click"....80/80.

This sound like a sticking valve, or just some crud in the seat, or maybe even just a piston ring that had not seated? This all happened so fast that I could not evaluate if there was air leaking out the exhaust.

I have been running with 100LL and adding 1oz/10 gallons of TCP. Some of my fellow airport rats are suggesting adding 4oz/10 gal of Marvel Mystery Oil as well to aid in upper end lubrication and prevent any tendancy for valve stem sticking.

Seems to me that TCP *and* Marvel Mystery Oil would be a bit of overkill. Any thoughts??

I must point out that I have never had any indication of sticking valves with this engine, just this temporary poor compression reading.

Thanks for the help/advice gang
 
I'd try this first....

painless said:
In checking compressions, I found that I was only getting 39/80 in #3 cylinder. I should preface this by saying that I have noticed no indication that the engine was in distress at all.
Click to expand...

If you have a sticking valve you will notice it in flight and it will scare the you know what out of you because your engine will sound like it had one spark plug wire removed.

This is something that I've found with doing many leakdown tests.

If you hear leakage and are seeing the 39/80 the valve is more than likely shut but has a small amount of carbon stuck between the valve and seat.

Take the rocker cover off ok. Find a rubber mallet and tap on the rocker arm where it contacts the valve stem lightly while doing the leakdown test. What this will do is allow the air that is pressurized in the cylinders to blow out any soot or minor carbon from between the valve and seat. You will hear and see a big difference in your leakdown test if everything is OK. The valve should come back on the seat at each rap of the mallet and the leakdown should show some good numbers. If not you have a problem and you should get a second opinion. Do the simple things first then go from there. I've seen engines with bad leakdowns and there is nothing wrong with them because of not spending the time to do what I mentioned above, but some A&Ps will try to sell you into removing the cylinders for no reason and get into your pocket. :p

This is a good idea to perform as stated as well.
Lycoming SB388C

--------------------------------------------------------------------------------

Time to perform the infamous Lycoming Valve Wobble Test.

http://www.lycoming.com/support/pub...pdfs/SB388C.pdf

If your guides are shot, the next occurrence could be a exhaust valve breakage...

Look for someone around that has the tool required....

gil in Tucson ....just failed this test with 600 hrs on my Tiger on a Lycoming overhauled O-360....
__________________
Gil Alexander
EAA Technical Counselor
RV-6A VSB (Very Slow Build)
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
Click to expand...
Click to expand...
 
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Cylinders

But does he have lycoming cylinders and valve train? I think Alan has some good advice here.
 
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painless said:
Seems to me that TCP *and* Marvel Mystery Oil would be a bit of overkill. Any thoughts??
Click to expand...

Not overkill at all------they do two different things.

TCP is a lead scavenger, helps to keep the plugs from fouling mainly.

Marvel is a lubricant, supposed to help the valves keep from sticking in the guides---------although some contend that at the temps exhaust valves live at any MMO that survives the combustion process wont be able to do any good for the exhaust valve.

I have used both TCP, and MMO for the last 20 years in my Stinson, and have had very little problems with lead fouling, and no sticking ex valves. This is in a Franklin engine with a whopping 5.5 compression ratio (IIRC).

YMMV however--------------

Mike
 
All cylinders....

LifeofReiley said:
But does he have lycoming cylinders and valve train? I think Alan has some good advice here.
Click to expand...

They all use the same valves (or PMA equivalents) and valve guides. The parts are meant to be interchangeable....

I believe the Lycoming SB388C should be applicable to other guys cylinders as well...

This ECI document (section 2.0) also says this....

http://www.eci2fly.com/pdf/96-3.pdf

gil in Tucson
 
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Marvel...

We used to have an occasional leaky valve on the old Pratt and Whitney 1340 cu. in. engines and Marvel Mystery oil sure brought the compressions up and the leak by the exhaust stopped.

We attached a 1/4" clear tubing to the blower inlet and sucked it staight out of the can while the engine belched blue smoke and coughed but it cleared up.

I've seen guys tape a tube to the intake with duct tape and the other end attached to a squirting oil can filled with Marvel. While the engine is running at a fast idle, a helper squirts the Marvel and it's sucked though the carb.

Regards,
 
Thanks for the input guys. This is a midtime engine with all Lycoming parts.

We were going to do the tap the rocker arm trick next if my lean runup did not help. Since it did and I now have 80/80 in that cylinder, we backed off doing that.

My plan is to try the MMO along with the TCP I am using and keep an eye on things. As I said before, I have had absolutely no indication of a stuck valve...nothing in flight and no "morning sickness". My bet is that it was a chunk of carbon in the way.


Regards,
 
You will want to know this

http://www.aslcamguard.com/
Now FAA Accepted
"...The result is fewer deposits, which dramatically reduces the chance of sticking piston rings or valve guide ?morning sickness?...."
Be sure to view the slide show.

OK, I am very opinionated on oils and additives, but really, you have a choice between something with "mystery" in its name or a new, FAA approved product developed by Ed Kollin, former Director of the Engine Research Laboratory, Advanced Fuels and Lubricants Group at Exxon. You also can choose http://www.avblend.com/ which is also FAA accepted, but with some negative considerations when you look at the FTC vs. their automotive version of the additive. AvBlend has some impressive aviation endorsements, at least. You could even choose http://www.microlon.net/aircraft.shtml which is also FAA accepted.

My personal opinion, based on some reasearch and some common sense is that Microlon is unlikely to be effective in most cases, anecdotal evidence notwithtanding. Further, I suspect that AvBlend is not as good as claimed if it's even useful. I think Mr. Kollin is the real deal.
I choose CamGuard for my engine. Please, no flames, just reasoned debate.

Just a reminder that FAA acceptance of an oil additive means only that it did no harm, not that it worked or worked as claimed.
 
Gary Bricker

The stationary engines used in industrial applications use Marvel to reduce carbon buildup. It is induced into the intake with a drip system. It works. The certified folks don't like it because Marvel will not go thru the process of getting it approved. Tooooo much hassele
 
My plan is to try the MMO along with the TCP I am using and keep an eye on things. As I said before, I have had absolutely no indication of a stuck valve...nothing in flight and no "morning sickness". My bet is that it was a chunk of carbon in the way.
Click to expand...

Jeff, hopefully you have resolved the low compression on your engine. I had a similar experience with the #4 cylinder on my 450hr engine (new Millenium cylinders in 2000). Over the course of a year I went through a few episodes where I could pull the prop through compression and one cylinder would be soft and air could be heard hissing out the exhaust. Each time I would dose the engine with MMO, fly the engine briskly and the problem would disappear. At no time did I experience the classic "stuck valve" in flight, only a very slight roughness when I would retard the throttle when entering the pattern. The engine never caught morning sickness, either. After a couple of cases of using the hammer to try to reseat the valve, I performed the rope trick, and lapped the exhaust valve, but the periodic problem still surfaced.

After a particularly stubborn episode, I decided I had seen enough and pulled the #4 cylinder. The valves were so tight in the guides they had to be driven out of the cylinder. After reaming the guides in #4, lapping the valves, honing the cylinder and tossing in a new set of rings, the engine has been happy for the past 200 hours.

Hopefully your problem has been resolved, but if it reappears a couple of times you may be looking at pulling the cylinder (not a particularly big deal) and actually fixing the problem. I've been told that tight valves are not uncommon with Lycomings.
 
Same Parts

az_gila said:
They all use the same valves (or PMA equivalents) and valve guides. The parts are meant to be interchangeable....

I believe the Lycoming SB388C should be applicable to other guys cylinders as well...

This ECI document (section 2.0) also says this....

http://www.eci2fly.com/pdf/96-3.pdf

gil in Tucson
Click to expand...

Hi Gil,

I understand the parts being the same and/or PMA equivalents, my thought was assembly and the quality control aspect. Getting a nice valve to valve guide fit takes just a little extra time but pays off in the long run. I had all of my jug wear part go through a cryogenic process and then properly fitted to deal with premature wear and valve sticking issues. Mine are ECI cylinders and came with a nice valve to guide fit directly from ECI. Do you know if Superior has a document out on this subject?
 
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Thanks Sam. I agree that if this is a persistant problem, I will definitely pull that cylinder.

As with most things in life, we all generally hope for an easy cure.... :rolleyes:

Regards,
 
yes on Superior...

LifeofReiley said:
Hi Gil,

I understand the parts being the same and/or PMA equivalents, my thought was assembly and the quality control aspect. Getting a nice valve to valve guide fit takes just a little extra time but pays off in the long run. I had all of my jug wear part go through a cryogenic process and then properly fitted to deal with premature wear and valve sticking issues. Mine are ECI cylinders and came with a nice valve to guide fit directly from ECI. Do you know if Superior has a document out on this subject?
Click to expand...
Yep... Superior says the same thing... which makes sense... :)

"These Millennium Standard Cast? aircraft cylinder assemblies are to be installed, operated and maintained in accordance with the applicable original equipment manufacturer?s overhaul and operator?s manuals or other applicable service documents. Failure to comply with these instructions may result in damage to the cylinders and/or engine or render them unsafe."

In this document...

http://www.superiorairparts.com/TechSupport/ServiceLetters/L00-07.pdf

I think the valve issues may be more operational than initial assembly issues. Heat can cause oil to coke up the guide, and lack of oil can cause wear. The valve wobble test SB388C has numeric limits for both too loose and too tight valve stems.

The oil supply to the valve stems is somewhat questionable... long, detailed article (and I guess somewhat controversial) here...

http://www.prime-mover.org/Engines/Marvel/tbo3.html

gil in Tucson - My Tiger cylinders are presently with Bill Scott who co-wrote the article...
 
Good Info

az_gila said:
Yep... Superior says the same thing... which makes sense... :)

"These Millennium Standard Cast? aircraft cylinder assemblies are to be installed, operated and maintained in accordance with the applicable original equipment manufacturer?s overhaul and operator?s manuals or other applicable service documents. Failure to comply with these instructions may result in damage to the cylinders and/or engine or render them unsafe."

In this document...

http://www.superiorairparts.com/TechSupport/ServiceLetters/L00-07.pdf

I think the valve issues may be more operational than initial assembly issues. Heat can cause oil to coke up the guide, and lack of oil can cause wear. The valve wobble test SB388C has numeric limits for both too loose and too tight valve stems.

The oil supply to the valve stems is somewhat questionable... long, detailed article (and I guess somewhat controversial) here...

http://www.prime-mover.org/Engines/Marvel/tbo3.html

gil in Tucson - My Tiger cylinders are presently with Bill Scott who co-wrote the article...
Click to expand...

Good info again Gil!

Thanks :cool:
 
Great Info

Gil,

Thanks for the great info researched by Bill Marvel and Bill Scott. I read the whole thing and it makes great sense to me. I have a Rotax on my Searey which does not suffer from any head/valve problems. Of course, Rotax heads are cooled by water. My Frycoming already has a suspect valve at 375 hours. I have not had any operational problems or low compression readings, but a recent bore scoping did show carbon blown off a portion of the face on the #4 exhaust valve. The other three are evenly coated. Hopefully it was just a random thing and will coat back up normally.

Getting back to Jeff?s question on MMO, it seems increasing the lube factor of the fuel swirling around exposed valve stems would help. However, if it is all burned in the combustion phase, then that?s not going to help the exhaust valve much which is the weak point. What has been the experience of those who have experimented with fuel lubes? How would it affect the Octane? Anybody have any good Links to info on this as it relates to air not-so-cooled aircraft engines? :confused:
 
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