Valve Rotators on Superior cylinders.

[abushey123]

Hello Everyone,
I have been having some trouble sense I replaced my engine with sticking exhaust valves. The cylinders have just shy of 600 hours on them and were new Millennium Cylinders 2016. I am getting about 100-125 hours before I start having issues with sticking valves and have to pull them and clean the guides and stems. This problem normally shows its self in flight with increased vibration and lack of power or after about an hour or two cool down and restart it will stick a valve until the engine warms back up. I have tried marvel in the oil and the gas, Changing ratios of car gas to 100LL, and a couple other additives with no luck. I normally see 300-350* CHT and 180ish on the oil temp. I normally run 2450-2500RPM in cruise. I know ECi cylinders came with valve rotators and I have not heard of people having issues with sticking valves on those cylinder. Can anyone shed light on part numbers for the valve springs and rotators? I would be curious if they would fit in the Millenniums. Any advice or old tricks to keep valves from sticking would be greatly appreciated.

[Bruce Fenstermacher]

No. you can't fit rotators on any cylinder, TCM or Superior, for a C-145/0-300. And BTW rotators may help but they don't eliminate valve sticking or Lycoming wouldn't have a airworthiness limitation of 1000 hours between performing their valve guide clearance procedure on their 0-390 engines which have rotators. Lycoming actually has an SB on ALL of their engines for this inspection in as little as every 300 hrs for helicopter engines but 400 hrs for all others. This SB of course is not mandatory so nobody does it until they have sticky valves. The 0-390 it is a airworthiness limit and it must be done or your engine is not airworthy. I had to ream 2 guides on the 1250 hr 0-390 I did that was operated in an unairworthy state the last 250 hrs.

I would suggest that perhaps the exhaust valve guides in your Superior cylinders are a fit tight. Normally you would think this a good thing. It is not. If they were fit as tight as allowed by spec, they will stick. Just a mater of time. May sound counter productive but I would fit (ream) them to no tighter than the middle of the normal usable tolerance. I haven't looked that up in a long time.

[sfarringer]

While ECI's O-300 cylinders did have exhaust valve rotators, Continental's purchase of ECI relegated ECI cylinders to the history books.

Special valve springs were used along with the rotocoil.

AEC531629 Rotocoil Assembly
AEC531609 Spring, Valve, Outer
AEC531610 Spring, Valve Intermediate
AEC531611 Spring, Valve, Inner

Probably not too likely to be easy to find, and a basis of approval for use on other brands of cylinders is not likely to exist.

I did not have any stuck valves while running ECI cylinders on my O-300.
But for reference, I have not had any stuck valves with my Superior cylinders either....

[GAHorn]

Hello Everyone,
I have been having some trouble sense I replaced my engine with sticking exhaust valves. The cylinders have just shy of 600 hours on them and were new Millennium Cylinders 2016. I am getting about 100-125 hours before I start having issues with sticking valves and have to pull them and clean the guides and stems. This problem normally shows its self in flight with increased vibration and lack of power or after about an hour or two cool down and restart it will stick a valve until the engine warms back up. I have tried marvel in the oil and the gas, Changing ratios of car gas to 100LL, and a couple other additives with no luck. I normally see 300-350* CHT and 180ish on the oil temp. I normally run 2450-2500RPM in cruise. I know ECi cylinders came with valve rotators and I have not heard of people having issues with sticking valves on those cylinder. Can anyone shed light on part numbers for the valve springs and rotators? I would be curious if they would fit in the Millenniums. Any advice or old tricks to keep valves from sticking would be greatly appreciated.

Valve rotators are for the purpose of providing even wear on valve-to-seat area and more even heat-transfer from valve to seat/head. They cannot be transferred to Superior or Continental cylinders without a basis of approval.

I would recommend that you stop using unapproved additives in your engine and fuel, not only because they are unapproved but also because we have no data to support that they will reduce valve-sticking…in fact, may actually contribute to the problem (as you have indicated you have used various additives in unknown quantities or characteristics or even what the mfr’r intends their additive to accomplish in aircraft engines….and we certainly have no data to show how those additives may react with aviation oils (presuming you are using only aviation oils.)

It’s been my observation that valve sticking often occurs in engines which are shut-down after a flight with little or no “cool-down” period. It’s good practice to run the engine 2-3 minutes at low rpm to allow temps to stabilize before shut down to avoid valve sticking. (The differences in alloys used in the valve train result in different rates of dimensional changes and a rapid shut down of a hot engine can result in stuck valves….which may result in trouble during start. This is the symptom you specifically mention to be your experience.)

Your experience of stuck valves in-flight…(presuming it occurred at cruise)…would indicate to me of improper clearances of valve-stem to guide. Your efforts to correct that have been “cleaning” (but no mention of reaming or actual clearance checks…although at 600 hrs I’m surprised this problem would just now show up if clearance was the issue)….so I wonder if your stuck valves may have been experienced during a large power or airspeed change..?? For example, after an altitude change? or other large configuration change..?

You mention blending mogas with avgas… I presume you do that to reduce the over-all leading burden..?? What ratio do you use? Do you lean your engine at all power settings..or any particular method?

[DaveF]

Lycoming actually has an SB on ALL of their engines for this inspection … This SB of course is not mandatory so nobody does it until they have sticky valves.

The heck you say!

[cessna170bdriver]

ALL stuck valves (and rings) I’ve ever had in 2300 hours on my O-300 were due to carbon build up (never lead). Switching away from mogas back to 100% 100LL solved the issue for me. (As I’m the only one I’ve ever heard of who solved the issue this way, I can’t say it’ll work for anyone else).

[Bruce Fenstermacher]

Lycoming actually has an SB on ALL of their engines for this inspection … This SB of course is not mandatory so nobody does it until they have sticky valves.

The heck you say!

6398F3DD-8397-417E-A676-31F6C8CB433C.jpeg

40 years ago one of my first owner maintenance tasks I took on on my new to me run out '67 Cherokee with Lycoming 0-320, was "the wobble " test. Valve guide clearance failed. At 2200 hrs the fit was to loose. (not the intended reason to do the test). After removing the cylinder I decided I'd rather fly and was perhaps in a bit over my head and confided in a local A&P. He said, what did you take off that cylinder for? Of course that guide is to loose. DON'T ever do that or this SB again. Over the next 40 years one might think with an SB that is called for every 400 hrs, for the most part, I'd of heard of at least some owner who has done or had the SB performed and wasn't happy to find their otherwise well running engine, out of compliance. But I just have not heard this. Of course I've heard about "morning sickness" and I've become extremely familiar with reaming small Continental valve guides, but it just not a hot topic amongst Lycoming owners. Today I'm twice the age and have 4 times the experience in all things mechanical in our shop than all the mechanics. When the "wobble test" came up with the 0-390, no one (besides me) knew there was an SB for such a thing let alone had ever seen it done. Of course I mentioned to them I'd done it once before they were a twinkle in their parents eye. But I'd swore I'd never do it again.

And so I make a bold statement that NOBODY does it. And DaveF produces, a picture of a person wearing a glove performing the SB. I presume the glove was to preclude any finger print data being left behind preserving plausible deniability.

All I can say Dave, if that is your gloved hand, is that you are just not NOBODY.

[abushey123]

Valve rotators are for the purpose of providing even wear on valve-to-seat area and more even heat-transfer from valve to seat/head. They cannot be transferred to Superior or Continental cylinders without a basis of approval.

I would recommend that you stop using unapproved additives in your engine and fuel, not only because they are unapproved but also because we have no data to support that they will reduce valve-sticking…in fact, may actually contribute to the problem (as you have indicated you have used various additives in unknown quantities or characteristics or even what the mfr’r intends their additive to accomplish in aircraft engines….and we certainly have no data to show how those additives may react with aviation oils (presuming you are using only aviation oils.)

It’s been my observation that valve sticking often occurs in engines which are shut-down after a flight with little or no “cool-down” period. It’s good practice to run the engine 2-3 minutes at low rpm to allow temps to stabilize before shut down to avoid valve sticking. (The differences in alloys used in the valve train result in different rates of dimensional changes and a rapid shut down of a hot engine can result in stuck valves….which may result in trouble during start. This is the symptom you specifically mention to be your experience.)

Your experience of stuck valves in-flight…(presuming it occurred at cruise)…would indicate to me of improper clearances of valve-stem to guide. Your efforts to correct that have been “cleaning” (but no mention of reaming or actual clearance checks…although at 600 hrs I’m surprised this problem would just now show up if clearance was the issue)….so I wonder if your stuck valves may have been experienced during a large power or airspeed change..?? For example, after an altitude change? or other large configuration change..?

You mention blending mogas with avgas… I presume you do that to reduce the over-all leading burden..?? What ratio do you use? Do you lean your engine at all power settings. Or any particular method?

George, I believe many would agree with me in saying valve rotators are also designed to reduce the risk of sticking valves to do carbon build up. Yes they do provide a method for even wear to stems and guides, but that's not to say they don't also even out carbon deposits which would intern reduce the risk of sticking valves. A quote from Helical Technology (the manufacture of porsche egr systems) "Valve rotators help to reduce the amount of carbon deposits on the valve and prevent carbon build-up on the valve seat. Cleaner valves reduce engine emissions and prevent burning and guttering of the valve face and seat". I have used Marvel Mystery oil in recommended quantities in both oil and gas with varying levels of success. Of course the oil gets changed every 50 hours and sent to the lab. They have not reported any anomalies in metal deposits. As far as additives in the fuel, I have tried sea foam and LIQUI MOLY valve clean in recommended quantities which has shown success in smaller single and twin cylinder air cooled engines (which honesty is just a smaller version of the o300). This treatment did clear some deposits off the piston but its difficult to inspect the valve stem through a spark plug hole.
When I have cleaned the guides and stems, I have used a straight hone greased and lubricated in the middle of the tolerance then used a ball gauge to ensure the guide is still under the upper limit. For the stem, I use kroil and a green scotch brite.
The sticking valves seem to be intermittent at normal ( leaned) cruise. These vibrations which I suspect are caused by this become more apparent in a climb after the engine has been running for a bit.
As far as the blending mogas with avgas, I do it simply because its cheaper to operate. I have the joys of living in ak so we don't have to worry about ethanol. I run 90 or better when mixing and often mix 30 car gas 70 100ll.
As far as leaning goes, I lean at all rpm or in curse. Lead till it runs rough and turn it in until it clears up.

[DaveF]

40 years ago one of my first owner maintenance tasks I took on on my new to me run out '67 Cherokee with Lycoming 0-320, was "the wobble " test. Valve guide clearance failed. At 2200 hrs the fit was to loose. (not the intended reason to do the test). After removing the cylinder I decided I'd rather fly and was perhaps in a bit over my head and confided in a local A&P. He said, what did you take off that cylinder for? Of course that guide is to loose. DON'T ever do that or this SB again. Over the next 40 years one might think with an SB that is called for every 400 hrs, for the most part, I'd of heard of at least some owner who has done or had the SB performed and wasn't happy to find their otherwise well running engine, out of compliance. But I just have not heard this. Of course I've heard about "morning sickness" and I've become extremely familiar with reaming small Continental valve guides, but it just not a hot topic amongst Lycoming owners. Today I'm twice the age and have 4 times the experience in all things mechanical in our shop than all the mechanics. When the "wobble test" came up with the 0-390, no one (besides me) knew there was an SB for such a thing let alone had ever seen it done. Of course I mentioned to them I'd done it once before they were a twinkle in their parents eye. But I'd swore I'd never do it again.

And so I make a bold statement that NOBODY does it. And DaveF produces, a picture of a person wearing a glove performing the SB. I presume the glove was to preclude any finger print data being left behind preserving plausible deniability.

All I can say Dave, if that is your gloved hand, is that you are just not NOBODY.

The first time I did the valve wobble test, it was on the engine at 2200 SMOH, and what do you know, the guides were out of spec wide! One of them was blowing oil past an exhaust gasket, and it looked exactly like a cracked cylinder. Had me going for a while until I sprayed Magnaflux SpotCheck white powder on it and saw the real source of the oil.

The check in the picture was at 600 SMOH, and the wear was right in the middle of the acceptable range, so I expect to be out of spec wide at TBO. I'm never checking again!

[n2582d]

Valve rotators or rotocoils have been discussed here. Unfortunately, the ECI links there have been hijacked by some scantily-clad Japanese vixens. Here’s ECI Service Instruction 02-8.

I’m attending two weeks of traning at Continental. Today the instructor happened to be talking about rotocoils. According to him, the primary purpose of a rotocoil is, as George stated, “for the purpose of providing even wear on valve-to-seat area and more even heat-transfer from valve to seat/head.” However, he did say they are also effective in reducing valve sticking. STC 10129SC is for the rotocoils on O-300 cylinders. I see no reason this STC cannot be applied to other brands of cylinders — except for the fact that Continental no longer sells it. The STC requires shorter valve springs. On the larger bore Continental engines they use an exhaust rocker that has two oil holes. One aimed at the valve/guide and the other aimed at the rotocoil. This apparently is not part of the STC for the O-300. Continental used to have rotocoils on the intake valves too. Service Information Letter SIL 94-10 calls for their removal “to improve intake valve seating performance.”