Marvel Mystery oil and TCP??

painless · #1 04-08-2007, 08:52 PM

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

LifeofReiley · #2 04-08-2007, 09:04 PM

Can you give more info on the engine? Overhaul, Reman, engine builder, reman cyl, new cyl?

az_gila · #3 04-08-2007, 09:12 PM

Time to perform the infamous Lycoming Valve Wobble Test.

http://www.lycoming.com/support/publ...dfs/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....

rv969wf · #4 04-08-2007, 09:56 PM

[quote]

Quote:

Originally Posted by painless

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.

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.

Quote:

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

LifeofReiley · #5 04-08-2007, 09:59 PM

But does he have lycoming cylinders and valve train? I think Alan has some good advice here.

Mike S · #6 04-08-2007, 11:28 PM

Quote:

Originally Posted by painless

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

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

rv8ch · #7 04-09-2007, 12:24 AM

There is another product that you might want to try instead of TCP - it's called Decalin Chemicals Runup.

http://www.decalinchemicals.com/

It seems to be much safer to ship and carry in the cockpit.

az_gila · #8 04-09-2007, 02:33 AM

Quote:

Originally Posted by LifeofReiley

But does he have lycoming cylinders and valve train? I think Alan has some good advice here.

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

pierre smith · #9 04-09-2007, 05:30 AM

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,

painless · #10 04-09-2007, 07:50 AM

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,