The Rope Trick - Stuck Valves

[N1478D]

The rope trick is a valuable trick in your bag of tricks, here is how it works:
The first step is to pull the prop thru listening for the sound of the intake/exhaust sound for each cylinder. This is very easy and intuitive, a bad cylinder has an obviously different feel and sound than the others. We only heard 5 exhaust sounds, telling us we had one bad cylinder. The next step is to identify which cylinder is bad. We took the top 3 plugs out of the left side because I had felt a cold cylinder on that side. Cover a plug opening with your thumb, and pull the prop thru the compression stroke on that cylinder. On the good cylinders, when the valves are closed the piston will compress the air against your thumb - very easy to feel. On the bad cylinder, there will not be any air forced against your thumb, it is escaping thru the stuck valve. The idea with the rope is to cover the top of the piston with the soft rope, and using the prop, gently bring the piston up pushing the valve up. We fed about a foot of large tie down rope, leaving plenty hanging outside of the cylinder, into the cylinder. But any type or size of rope should work. The first attempt to gently push the valve up did not work. We removed the rope, pulled the prop thru, and repeated the process. The second or third attempt resulted in a pop, and the cylinder had compression. Minimum tools required would be socket and wrench for the spark splug, and open end wrenches for the leads.

[GAHorn]

It's a good idea when doing this trick to remember a few things.
1) Manila, cotton, or nylon rope is less likely to contain damaging trash to introduce into your cylinder or damage a piston, etc., especially if new rope.
2) When bringing the piston up against the valve, be gentle. You don't want to force anything, especially you don't want to place undue strain on a valve-head in such a way as to bend a valve.
3) Removing a rocker-box and administering a generous shot of Mouse-milk, WD-40, or other penetrating type oil to the area of the stuck valve-stem first, then going to have a cup of coffee while it soaks, ...can help ease things along.
Lastly, keep in mind that if it stuck once, it'll likely do it again. Not always the same valve, but usually. When you get it home, consider removing that valve's retainers and springs, dropping the valve down into the cylinder and reaming the valve guide or at least cleaning/polishing it out some (I've used gun-cleaning equipment successfully, not the bronze bristle brushes but swabs and patches with Hoppe's No.9, followed by LubriPlate assembly-grease), and fishing the valve back up into place and reinstalling it. (A slender magnet will help get it back in place, and compressed air such as when running a compression test will hold the valve up in place while you re-assemble the valve springs and keepers. All this lets you examine the valve stem through the spark-plug hole for scoring as well, and it is a great opportunity to check for broken springs, which can contribute to this problem yet be difficult to detect.)
If ever there was a use for Marvel Mystery oil, ...treating an engine with a history of stuck valves is it! Marvel is a light oil/solvent and can help free these things up. Follow directions on the can if you add it to fuel (preventative measures), or add a half-pint to the sump half-way through each oil change period. The first time you do this (if doing it to a mid-life or later engine), expect a lot of junk to be loosened up. So do it at the end of an oil change period, run only a short while, and drain the oil and clean the screen. This is because you're likely to wash a lot of junk loose inside a heavily coked-up engine if you've not been doing this regularly or on an on-going basis.
I'm only recommending this to an engine that has a history of stuck valves, not engines that haven't had such troubles. ( I don't use anything but aero-oil in my engine, but I haven't had any problems [knock on wood], and I change my oil every 25 hours or sooner without fail.)

[kens 170B]

I have experienced 5 stuck exhaust valves in the past month. Three happened at Sun n' fun, so we had to use the rope on those. We also reamed the guides and I flew the aircraft the 7 hours to my home field without a problem. After arriving home I experienced two more stuck valves (different cylinders). Now h

Here is the way that I am operating my 170 and I would appreciate you 170 drivers letting me know if I am doing something wrong.

I lean all of the time, after start, during taxi, during takeoff, cruise, approach and landing. I run the engine at 1800 rpms for 30 seconds and then reduce the rpm to 1200 and pull the mixture during shutdown.

I cruise ar 2450 rpm.

I have used TCP during the last 8 years in every tankof 100LL. I am convenced that TCP is not the answer to this problem because the O-300 does not develop enough heat to cause TCP to do the process that it is advertised to do.

What I plan to do in the future is the following:
Lean all of the time.
Use Marvel Mistery Oil in the fuel and oil.
Shut-down according to the FAA Fuel Pam. (as stated above).

Thanks for taking the time to respond

Kens 170B

[N1478D]

Hi Ken, I had a few changes before my stuck valve experience. One of them was that I had started leaning more agressively. One of my most trusted sources of aviation information, after I asked him his opinion of the stuck valve, advised me that leaning is good, but aggresive leaning may cause stuck valves. He also recommended because of the polution penalty here in the DFW area, that the auto gas I had started using was not good for the 170. Almost everyone has recommended Marvel in the fuel, and some have recommended it in the oil also, as a helpful remedy for stuck valves. I've heard pros & cons on your shutdown procedure. Mine has been on 6 flights since the stuck valve and has run fine. Keep us informed.

[GAHorn]

I'm convinced there are three basic reasons for valve sticking in these engines.
#3-Valve guides improperly reamed at installation, therefore being too tight.
#2-Valves not being completely replaced with new at overhaul, and/or subsequently being overheated and warped.
And the #1 reason for sticking valves is: Not allowing this engine to stabilize temperatures after flights prior to shutdown. The method used as described previously in this thread only adds additonal heat to the valve prior to shut-down. I believe that oil temps within the guide/valve stem area is heated excesively and not allowed to cool prior to shut down, which leads to oil coking (carbonizing). This builds up until the valve guide internal dimensions are reduced sufficiently that after shut-down the cooling process and the associated shrinking of the cooled guide seizes the valve-stem.
I personally treat my engine as if it were a turbocharged engine. I land, and subsequently taxi in to the ramp using minimum power. I let the engine cool several minutes before pulling the mixture. (I leave the mixture at the cruise setting throughout the descent and landing. In case of an emergency go-around I plan to enrichen the mixture.) But again, I leave the engine leaned during descent, landing, and taxi-in. After the cooling period at RPMs below 1000, I pull the mixture to kill it. I do not run it up in any "clearing" procedure. I believe that causes unnecessary heat cycles and again re-heats the valve and valve guides to their detriment. In 33 years of flying I've never suffered a stuck valve (knock on wood) except on my employer's new engine which had not had it's guides properly reamed. I use avgas and aero oils exclusively.

[4-Shipp]

Tom Downey showed me this shutdown technique when I flew his 170 last year. After landing, set 1100-1200 rpm, lean until it misses and then richen 'til smooth. Let it run like this for 1-2 minutes and then pull mixture to idle. I've got 40 hours now with 100LL and no additives and have had no problems. Thoughts?

Bruce

[GAHorn]

Well, I was surfing the 'net and ran across a response by the famous (or should be famous) Bill Scott, of Precision Engines. He has made a name for himself and his engine shop over the years with his research into Lycoming and Continental lubrication and valve systems. (Many may remember his articles regarding Lycoming and Continental valve lubrication issues.) Anyway, he's someone who seems to be methodical and knowlegeable about engines, particularly as regards valve systems and their lubrication. Here's a quote I lifted from his response to a question from one of his customers.

"In regards to the great Marvel Mystery oil debate. I have taken apart
hundreds of engines and then inspected them for wear. I have noted that valves stick when operation clearance are reduced from the normal .004"-.006" operating clearances to .0024" because of coked oil and lead deposits. I have noted that the use of MMO allows the valves to operate in some instances down to .0015" clearances before the valve stuck. My thought is, it does not replace SB388B because deposits still build up and valves still stick, although this takes place a little further down the line. MMO in the gas does cause the gaskets in the carb to swell, when squeezed between fingers these gaskets ooze red oil. I did hear a few years ago that a study indicated MMO relieved stiff joints-arthritis, god only knows what else it can do. MMO is not approved. No, I am not a chicken, but there is none in my aircraft and there will not be in the future, ..."

I don't know that red oil oozing from carb gaskets is a problem, although swelling might be. I'm not sure what conclusion to draw from his comment, other than to wonder - "What does it matter as long as valves do not stick as often with it as they do without it?"
I think my own position is, ...If you are having sticking valves and do not wish to mechanically correct the problem,...then you might try Marvel Mystery Oil and see if it works for you.
If you don't have sticking valves, (or if you do and don't mind fixing them properly by partial disassembly and corrective valve/valve guide work)...then don't use it. Why run the risk of swollen gaskets if you don't have to? It'd sorta be like Lee Marvin sang in "Paint Your Wagon",...Cured of what you're sufferin' from and suffrin' from the cure!

[zero.one.victor]

George,I thought I had you all squared away on this. You must first consecrate your beaker of Marvel Mystery Oil by holding it aloft & bowing toward Wichita,then do the hokey-pokey while chanting "car gas,car gas, sis boom bah". Works like a charm! I've put over 750 hours on my 170 in the past 5 years using car gas & MMO with nary a stuck valve. A broken connecting rod,yes,but Marvel doesn't make any claims about that!

Eric

[mit]

<Snip>



It'd sorta be like Lee Marvin sang in "Paint Your Wagon",...Cured of what you're sufferin' from and suffrin' from the cure![/quote]


Oh my god, I thought I was the only one in the world that would admit to watching Paint Your Wagon!

[sj]

A very good thread for the new continental 300 owner, thanks!

sj

[flyguy]

Way back in the "yahoo years" we went through oil and gasoline "add-ins". Seems like we debated about putting different things in our fuel and oil tanks. Did anyone save those posts?

MMO will loosen things up temporarily but it just puts off the inevitable. Carbon/lead deposits will eventually stick valve stems that are too tight to begin with. Many repair facilities do not give enough clearance in valve guides and do not grind the valve faces and seats to scavenge exhaust gasses properly. More clearance in the guides won't cause unusual wear during normal engine TBO. It will extend time between overhaul and having to address abnormal valve sticking. Increasing the valve and seat scavenging properties will do just as much or more.

My FOR WHAT ITS WORTH.

[N1478D]

Way back in the "yahoo years" we went through oil and gasoline "add-ins". Seems like we debated about putting different things in our fuel and oil tanks. Did anyone save those posts?

MMO will loosen things up temporarily but it just puts off the inevitable. Carbon/lead deposits will eventually stick valve stems that are too tight to begin with. Many repair facilities do not give enough clearance in valve guides and do not grind the valve faces and seats to scavenge exhaust gasses properly. More clearance in the guides won't cause unusual wear during normal engine TBO. It will extend time between overhaul and having to address abnormal valve sticking. Increasing the valve and seat scavenging properties will do just as much or more.

My FOR WHAT ITS WORTH.

I don't know Gary, I quit using Marvel and my valve stuck. I started using Marvel again, and over 100 hours later, no stuck valve. It does seem like some engines do not need Marvel, but mine likes the stuff. Maybe it is related to fuel supply, atmospheric conditions, etc or something that it is had to logically determine.

[GAHorn]

Way back in the "yahoo years" we went through oil and gasoline "add-ins". Seems like we debated about putting different things in our fuel and oil tanks. Did anyone save those posts?

MMO will loosen things up temporarily but it just puts off the inevitable. Carbon/lead deposits will eventually stick valve stems that are too tight to begin with. Many repair facilities do not give enough clearance in valve guides and do not grind the valve faces and seats to scavenge exhaust gasses properly. More clearance in the guides won't cause unusual wear during normal engine TBO. It will extend time between overhaul and having to address abnormal valve sticking. Increasing the valve and seat scavenging properties will do just as much or more.

My FOR WHAT ITS WORTH.

I don't know Gary, I quit using Marvel and my valve stuck. I started using Marvel again, and over 100 hours later, no stuck valve. It does seem like some engines do not need Marvel, but mine likes the stuff. Maybe it is related to fuel supply, atmospheric conditions, etc or something that it is had to logically determine.

Joe, maybe if you could pick up your cruising speed a bit, your valves would get more cooling air and wouldn't overheat, swell-up and seize!

[N1478D]

Way back in the "yahoo years" we went through oil and gasoline "add-ins". Seems like we debated about putting different things in our fuel and oil tanks. Did anyone save those posts?

MMO will loosen things up temporarily but it just puts off the inevitable. Carbon/lead deposits will eventually stick valve stems that are too tight to begin with. Many repair facilities do not give enough clearance in valve guides and do not grind the valve faces and seats to scavenge exhaust gasses properly. More clearance in the guides won't cause unusual wear during normal engine TBO. It will extend time between overhaul and having to address abnormal valve sticking. Increasing the valve and seat scavenging properties will do just as much or more.

My FOR WHAT ITS WORTH.

I don't know Gary, I quit using Marvel and my valve stuck. I started using Marvel again, and over 100 hours later, no stuck valve. It does seem like some engines do not need Marvel, but mine likes the stuff. Maybe it is related to fuel supply, atmospheric conditions, etc or something that it is had to logically determine.

Joe, maybe if you could pick up your cruising speed a bit, your valves would get more cooling air and wouldn't overheat, swell-up and seize!

Yhea, I use to go cruising! And, swelling up and a seize has a hole new meaning now that I am past 50!

[Rudy Mantel]

Joe, how much MMO do you add to your oil and fuel ?
Rudy