Excitement on Climb Out (rough running engine)

[lr172]

Have a buddy that’s an A&P and IA for a large aviation company that does photo and terrain mapping. They use a variety of planes including C-206s and C-414s. They do a lot of long missions and the bosses are always trying to save fuel so directed the pilots to run exclusively LOP and they had very frequent stuck valves. He insisted they start running peak or ROP and they stopped having exhaust valve issues completely. Yes it cost more fuel but way outweighed the extra maintenance costs and aircraft downtime and lost contracts. I’m not a mechanic, just repeating what I heard so don’t shoot the messenger.

That also is a small sample size. I suspect a pretty large percentage of folks here on VAF run LOP and it would seem that chronic sticking valve issues are not that common. Maybe a poll would show that. I suspect there is a variable related to the type of highly repeatable work that operation does that would make this relationship with mixture unique. It is certainly not universal, as I always run LOP and have 1400 hours on my 320 with no sticking valves; I am certain I am not the only one. Until the time that we fully understand this phenomon and it's root cause, applying causal relationships, like mixture, is really a dartboard exercise. It could be a long time, as Lyc doesn't really seem to care and they are probably the only ones with enough $ to fully test and figure it out. With a two year waiting list to buy their products with this problem, why should they care, as it just minimizes the pile of cash they are raking in. Until then we just get the rampant speculation we have today.

 

[mfleming]

Whose oil are you using?

Phillips X/C 20W-50 with the recommended amount of Camguard. My last oil change I switched to Phillips Victory 20W-50 with the Camguard already in it.

 

[georgemohr]

Most will say that #2 is their hottest cylinder on a 14 with an IO-390, so that could very well be impactful.

 

[RV-9erA]

I must say -- ever since I started using Marvel's Mystery Oil in my fuel (0.4 oz per gallon) and AvBlend during oil changes with AeroShell 15W-50, my days of stuck valves ended many years ago! Cylinder compression stays high and equal, and borescope pictures inside cylinders look much cleaner along with cleaner sparkplugs. Marvel's Mystery Oil also helps prevent a sticky fuel selector valve. There may be some naysayers out there, but I know it works and has for many years for me! I use it in everything internal combustion motor!

 

[Lkitson]

Phillips X/C 20W-50 with the recommended amount of Camguard. My last oil change I switched to Phillips Victory 20W-50 with the Camguard already in it.

I’ve been using Phillips Victory oil since my engine was new because I thought it had an anti-corrosion additive like Camguard. But I recently found out that the additive is just anti-wear.

Phillips Victory Oil: Not a CamGuard Blend - Aviation Consumer

Scuttlebutt and rumor—driven by ignorance, profit motive or competition—is that the Phillips AW and Plus Victory oils do the same thing as the CamGuard

aviationconsumer.com

For my next oil change I’ll still use the victory oil, but I’ll add Camguard

 

[Jetmart]

Phillips X/C 20W-50 with the recommended amount of Camguard. My last oil change I switched to Phillips Victory 20W-50 with the Camguard already in it.

I don't believe Phillips Victory 20W50 contains Camguard. Aviation Consumer say it does not.

Phillips Victory Oil: Not a CamGuard Blend - Aviation Consumer

Scuttlebutt and rumor—driven by ignorance, profit motive or competition—is that the Phillips AW and Plus Victory oils do the same thing as the CamGuard

aviationconsumer.com

 

[RV-9erA]

Most will say that #2 is their hottest cylinder on a 14 with an IO-390, so that could very well be impactful.

That's very interesting on the RV-14 with an IO-390 since Lycoming engines on RV's generally run hottest on cylinder #3 (right rear cylinder).

 

[mfleming]

I’ve been using Phillips Victory oil since my engine was new because I thought it had an anti-corrosion additive like Camguard. But I recently found out that the additive is just anti-wear.

Phillips Victory Oil: Not a CamGuard Blend - Aviation Consumer

Scuttlebutt and rumor—driven by ignorance, profit motive or competition—is that the Phillips AW and Plus Victory oils do the same thing as the CamGuard

aviationconsumer.com

For my next oil change I’ll still use the victory oil, but I’ll add Camguard

I don't believe Phillips Victory 20W50 contains Camguard. Aviation Consumer say it does not.

Phillips Victory Oil: Not a CamGuard Blend - Aviation Consumer

Scuttlebutt and rumor—driven by ignorance, profit motive or competition—is that the Phillips AW and Plus Victory oils do the same thing as the CamGuard

aviationconsumer.com

We’ll thats what I get listening to the local gurus instead of checking it out for myself

 

[turbo]

get the wobble test done!! it is the weakest part of your LYC. there is no magic solution to prevent it except testing and reaming out the guide. knowing what the measurement is feels good. if you burn 100ll use a fuel additive, decalin or tcp. this guy stuck a valve and still doesn't get it.

 

[georgemohr]

That's very interesting on the RV-14 with an IO-390 since Lycoming engines on RV's generally run hottest on cylinder #3 (right rear cylinder).

Yeah its a surprise to me. The #3 has a huge opening behind it in the baffle for the duct to the oil cooler. I'd have bet that would be hottest, but I think its pretty universal that #2 is. The only thing I can point to is the prop governor.

 

[mfleming]

Yeah its a surprise to me. The #3 has a huge opening behind it in the baffle for the duct to the oil cooler. I'd have bet that would be hottest, but I think its pretty universal that #2 is. The only thing I can point to is the prop governor.

I was just looking back on my previous flights and my #2 was the second coolest cylinder on average but never the hottest. So in my case, heat didn't appear to be a factor in the #2 exhaust valve sticking.

 

[ve0kog]

get the wobble test done!! it is the weakest part of your LYC. there is no magic solution to prevent it except testing and reaming out the guide. knowing what the measurement is feels good. if you burn 100ll use a fuel additive, decalin or tcp. this guy stuck a valve and still doesn't get it. View attachment 87535

what is the right course of action when you see the top of the piston looking like this?

 

[jrs14855]

what is the right course of action when you see the top of the piston looking like this?

Search Bill Marvel and get and education about the design flaws in Lycoming oil system. High green oil pressure on 0 320 and 0 360 parallel valve has served me well since mid 70's.

 

[RV-9erA]

Regarding additives -- AvBlend (Lucinite) during oil changes helps dissolve carbon build-up on pistons, valves and valve guides. It also wicks into metal parts keeping parts better lubricated between flights. Marvel's Mystery Oil in the fuel helps lubricate and clean the top-end because it has both a mild solvent and lubricant. As a mater of fact, in the old piston days, the military used Marvel's Mystery Oil (by the 50-gallon drum) to keep their radial engines from developing stuck valves and to maintain cylinder compression longer. Both Lucinite and Marvel's Mystery Oil were used in military aircraft.

 

[DCBrown198]

The number 2 cylinder on my relatively new (130 hour) IO-540 has morning sickness. Ordered the reamer from McFarlane and will get to work next week.

Bugs me that we have to deal with this on such expensive engines.

 

[mfleming]

The number 2 cylinder on my relatively new (130 hour) IO-540 has morning sickness. Ordered the reamer from McFarlane and will get to work next week.

Bugs me that we have to deal with this on such expensive engines.

When talking to Lycoming after I reamed the #2 exhaust valve guide, they recommend I submit a warranty claim. I passed on the warranty, as I did all the work and was out very little money. But, if I had paid someone to due the work, I certainly would have submitted a claim

 

[RV-9erA]

The number 2 cylinder on my relatively new (130 hour) IO-540 has morning sickness. Ordered the reamer from McFarlane and will get to work next week.

Bugs me that we have to deal with this on such expensive engines.

Makes a person wonder if this new trend of Phillips Oil plus CamGuard may actually have something to do with it. I've never used Phillips Oil nor CamGuard. But, I have owned several Lycoming engines (IO-360's and O-320's) without any valve sticking issues nor morning sickness, where this engine is 20-years old now with 1200 hours since reman, and it still starts-up and runs very smoothly with high compression on all cylinders and no metal in the filters.

 

[RV7 To Go]

Over 450 hrs in 4 yrs on my O-320 running Phillips XC20-50 and CamGuard with no engine issues. Over 800 hrs in 8 years on my O-360 (PV) running Phillips XC20-50 and CamGuard with no engine issues. Always cruised LOP around 60-65% power on the 360. Both ran high green oil pressures (85-90). Doing the same on my freshly overhauled IO-360 (PV) in the 8. Only 48 hrs so far so we'll see how it goes with this engine.

 

[RV-9erA]

Over 450 hrs in 4 yrs on my O-320 running Phillips XC20-50 and CamGuard with no engine issues. Over 800 hrs in 8 years on my O-360 (PV) running Phillips XC20-50 and CamGuard with no engine issues. Always cruised LOP around 60-65% power on the 360. Both ran high green oil pressures (85-90). Doing the same on my freshly overhauled IO-360 (PV) in the 8. Only 48 hrs so far so we'll see how it goes with this engine.

That's a good report on your engine history -- hope the new engine follows the same trend! After engine break-in, I use AeroShell 15W50, Avblend at oil changes and MMO in my fuel (0.4 OZ per gallon) -- the engine starts and runs silky-smooth every time! When I pull the prop though (4-blades) before the first start of the day, I can really feel that compression on every blade even after the engine sits for a few weeks. There's really something to this equation! The idea of running higher oil pressure sounds interesting -- this was done using the oil pressure relief valve adjustment? I assume you mean hot oil pressure? I also like running 60-65% power for local flights, but run on the ROP at generally 1200 F on the EGT. Borescope pictures and sparkplugs have always looked great, too!

 

[RV7 To Go]

The idea of running higher oil pressure sounds interesting -- this was done using the oil pressure relief valve adjustment? I assume you mean hot oil pressure?

Yes. Oil temps 85-90 hot in cruise. Around 105 at startup with cold oil. It was set using the pressure relief adjustment.

 

[olyolson]

Regarding additives -- AvBlend (Lucinite) during oil changes helps dissolve carbon build-up on pistons, valves and valve guides. It also wicks into metal parts keeping parts better lubricated between flights. Marvel's Mystery Oil in the fuel helps lubricate and clean the top-end because it has both a mild solvent and lubricant. As a mater of fact, in the old piston days, the military used Marvel's Mystery Oil (by the 50-gallon drum) to keep their radial engines from developing stuck valves and to maintain cylinder compression longer. Both Lucinite and Marvel's Mystery Oil were used in military aircraft.

I’ve always used Camguard but is AVblend any different?

 

[BoydBirchler]

I have freed a few stuck valves in my 50+ years of flying. All of them I freed were on #2. I have seen that the front 2 lobes on the Lycoming cams fail first, the second lobe from the front runs 2 lifters and was usually the first to fail. There seems from the evidence to be less oil circulating in the front of the case, than progressively further back.

All of the stuck valves I have seen/experienced had a tar like gooey residue, not hard carbon. What is the consistency of what you guys are seeing? Does your engine have extra oil squirts that spray oil on the cam lobes (like the Ney nozzle mod) and or oil squirts that spray on the under side of the pistons, like the angle valve engines? My inquiring mind would like to know.

 

[mfleming]

I have freed a few stuck valves in my 50+ years of flying. All of them I freed were on #2. I have seen that the front 2 lobes on the Lycoming cams fail first, the second lobe from the front runs 2 lifters and was usually the first to fail. There seems from the evidence to be less oil circulating in the front of the case, than progressively further back.

All of the stuck valves I have seen/experienced had a tar like gooey residue, not hard carbon. What is the consistency of what you guys are seeing? Does your engine have extra oil squirts that spray oil on the cam lobes (like the Ney nozzle mod) and or oil squirts that spray on the under side of the pistons, like the angle valve engines? My inquiring mind would like to know.

No oil squirters on mine and no gunk on the valve.
In my case I think the valve guide was not properly sized from Lycoming. In retrospect, my engine was exhibiting signs of a sticky valve very early in its life.

 

[mfleming]

OK, this is interesting but of course not definitive in any way.
I asked ChatGpt this question.

“Is there any data to support a theory that lycoming engines built during the height of Covid have more sticky valve problems?”

The reply:

“There is no official, peer-reviewed, or broadly published data from Lycoming or the FAA specifically linking increased sticky exhaust valve issues to engines built during the height of COVID (2020–2021)—but there is a credible theory and strong anecdotal evidence circulating among A&Ps and engine shops.

Here’s what’s known or reasonably inferred:

---

1. Anecdotal Trends from the Field​

• Many A&Ps, engine rebuilders, and IA mechanics have reported a noticeable uptick in sticky valve issues in Lycoming engines with serial numbers or manufacturing dates from 2020–2021.
• These reports appear across models: O-320s, IO-360s, and even some parallel-valve IO-540s.
• Most cases are low-time engines (under 300 hours), some as early as 20–100 hours.

---

2. The COVID Disruption Theory​

The working theory goes like this:

• During the early pandemic, Lycoming (and many suppliers) faced:
  
  • Reduced staffing
  • Interrupted supply chains
  • New or inexperienced labor due to sudden staffing changes
• Quality control may have suffered slightly:
  
  • Valve guides may have been reamed too tight
  • Incorrect or inconsistent lubrication during assembly
  • Tolerances that were in spec but on the tight end

---

3. Lycoming's Quiet Acknowledgment​

• While Lycoming has not issued a service bulletin or AD specifically about this issue being tied to COVID-era engines, they have:
  
  • Continued to expand guidance and tools for sticky valve inspection and remediation
  • Published Service Bulletin SB388C (Valve Guide Reaming)
  • Acknowledged that valve sticking is not unusual in low-time engines

Some mechanics interpret Lycoming’s continued emphasis on valve guide reaming tools as an indirect response to the uptick in these reports.

---

4. Additional Considerations​

• The increased use of aircraft at low power settings during training (which continued throughout COVID) may have contributed to lead buildup.
• Also, aircraft sitting idle for long stretches during lockdowns may have led to corrosion or deposit formation in guides.

---

Summary:​

There’s no official bulletin blaming COVID-era builds, but strong field evidence suggests engines assembled in 2020–2021 may have a higher-than-usual chance of tight valve guides, especially on cylinder #2, which tends to run cooler and is less prone to self-cleaning.”

As I said above, not difinitive but none the less interesting

 

[RV-9erA]

I’ve always used Camguard but is AVblend any different?

They work very differently. AvBlend (rebranded and FAA approved from Linkite formulated in 1948) is a micro-lubricant that penetrates, cleans, and protects engine components to help reduce wear, carbon buildup and rust, Not only is AvBlend an micro-lubricant, it actively dissolves carbon that can build-up on valve stems, valve guide and piston rings. AvBlend easily wicks into cam lobes, lifter surfaces and cylinder barrels and stays there. However, CamGuard mitigates corrosion and reduces wear by forming a thin protective chemical hard plastic like film onto metal surfaces that generate heat and friction. Therefore, AvBlend and CamGuard work very differently. I've been using AvBlend at oil changes ever since it got FAA approval in 1997 (28-years), and MMO in my fuel for about the same time. After that, I stopped getting sicky valves and "morning sickness". The first time I used AvBlend, it turned my oil black very quickly from dissolving all the carbon build-up in the engine. After several oil changes, the oil remained much cleaner.

 

[mfleming]

They work very differently. AvBlend (rebranded and FAA approved from Linkite formulated in 1948) is a micro-lubricant that penetrates, cleans, and protects engine components to help reduce wear, carbon buildup and rust, Not only is AvBlend an micro-lubricant, it actively dissolves carbon that can build-up on valve stems, valve guide and piston rings. AvBlend easily wicks into cam lobes and lifter surfaces. CamGuard mitigates corrosion and reduces wear by forming a protective chemical film on the metal surfaces itself. CamGuard's anti-wear chemistry creates a "plastic like" film on metal surfaces. This film is formed when the oil washes over the surfaces and heat is generated by friction. So, AvBlend and CamGuard work very differently. I've been using AvBlend at oil changes ever since it got FAA approval in 1997 (28-years), and MMO at about the same time. After that, I stopped getting sicky valves and "morning sickness". Odd how a suck valve seems to happen shortly after takeoff.

MMO in the fuel, oil or both?

 

[RV-9erA]

MMO in the fuel, oil or both?

I use MMO in the fuel only at every refueling (0.4 oz to every 1-gallon of fuel). And, AvBlend at every oil change (1-pint per every 8-quarts of oil). I also feel that AeroShell 15W50 is a better quality (simi-synthetic) oil than Phillips and has the Lycoming recommended additives.

 

[ve0kog]

AvBlend

from the product description:

"the oil molecules are too large to provide penetration in the small grooves and protect the entire surface of your engine. AVBLEND's depth-soaking molecules are small enough to fill in these tiny nooks and crannies and penetrate deep into the metal, thus providing better lubrication with moving pieces. Plus, AVBLEND cleans the surface from harmful deposits."

I'm a bit suspicious about all this metal "depth-soaking" and the molecule sizes. they are talking about nanometer scale imperfections in the surface that supposedly aveblen would penetrate but the regular oil could not. i don't buy it

 

[RV-9erA]

from the product description:

"the oil molecules are too large to provide penetration in the small grooves and protect the entire surface of your engine. AVBLEND's depth-soaking molecules are small enough to fill in these tiny nooks and crannies and penetrate deep into the metal, thus providing better lubrication with moving pieces. Plus, AVBLEND cleans the surface from harmful deposits."

I'm a bit suspicious about all this metal "depth-soaking" and the molecule sizes. they are talking about nanometer scale imperfections in the surface that supposedly aveblen would penetrate but the regular oil could not. i don't buy it

Not attempting to sell it -- just know it has worked for me for over 28-years now in two different aircraft (IO-360 and O-320) and over 20-years now in the RV-9A I built. Take a look at this video for that penetration question and the carbon dissolving property of AvBlend. I'm not a salesman -- your free to use anything you like! A stuck valve, shortly after takeoff, in a 4-banger can scare the crap out of any pilot, especially if it's your first stuck valve -- been there done that!

 

[Dugaru]

the oil molecules are too large to provide penetration in the small grooves and protect the entire surface of your engine. AVBLEND's depth-soaking molecules are small enough to fill in these tiny nooks and crannies and penetrate deep into the metal, thus providing better lubrication with moving pieces.

I am no physicist, by any stretch, but I agree this sounds somewhat fishy. Molecules are really, really, really small compared to all the “grooves,” “nooks,” and “crannies” that I’m familiar with.

 

[RV-9erA]

I am no physicist, by any stretch, but I agree this sounds somewhat fishy. Molecules are really, really, really small compared to all the “grooves,” “nooks,” and “crannies” that I’m familiar with.

Then why do they make penetrating oils instead of just using any oil for such applications?

Not attempting to sell AvBlend -- just know it has worked for me for over 28-years now in two different aircraft (IO-360 and O-320) and over 20-years now in the RV-9A I built. You're free to use anything you like. But a stuck valve, shortly after takeoff, in a 4-banger can scare the crap out of any pilot, especially if it's your first stuck valve. Been there a few times before using AvBlend during oil changes and MMO in the fuel. Haven't had a stuck valve since!

BTW -- we live in the Pacific Northwest and base at Paine Field (KPAE) near Seattle, so things can get damp up here, too!

 

[Dugaru]

Then why do they make penetrating oils instead of just using any oil for such applications?

Not attempting to sell AvBlend -- just know it has worked for me for over 28-years now in two different aircraft (IO-360 and O-320) and over 20-years now in the RV-9A I built. You're free to use anything you like. But a stuck valve, shortly after takeoff, in a 4-banger can scare the crap out of any pilot, especially if it's your first stuck valve. Been there a few times before using AvBlend during oil changes and MMO in the fuel. Haven't had a stuck valve since!

BTW -- we live in the Pacific Northwest and base at Paine Field (KPAE) near Seattle, so things can get damp up here,

Of course - viscosity is based on molecule size! I learned something today!

 

[jrs14855]

The Bill Marvel info says that at the front of the right gallery the oil pressure is approx 8 # less than at the rear of the gallery. I have not found anything definitive on the left side gallery pressure but it would appear to be slightly less than right side. That would coincide with the cam issues first appearing on the forward lobes.
One of my consultants does not like multi grade oil in the summer desert heat. Fine with it in the cooler weather. So for me its Aeroshell W100 with camguard.
1000 hours of brutal treatment of 0 360 parallel valve in Pitts with fixed pitch prop. 300 hours at 3500 rpm, the rest at 3300. Lot of rapid power changes from full throttle to idle. No oil filter, just the screens. 100W with no additives in the Pitts.

 

[BoydBirchler]

I use MMO in the fuel only at every refueling (0.4 oz to every 1-gallon of fuel). And, AvBlend at every oil change (1-pint per every 8-quarts of oil). I also feel that AeroShell 15W50 is a better quality (simi-synthetic) oil than Phillips and has the Lycoming recommended additives.

One thought is to substitute a good brand of 2 cycle oil instead for MMO to use in the fuel. The 2 cycle oil is made to lubricate and also to not foul the spark plugs during combustion.

 

[rv8ch]

One thought is to substitute a good brand of 2 cycle oil instead for MMO to use in the fuel. The 2 cycle oil is made to lubricate and also to not foul the spark plugs during combustion.

I'd take this pretty slow - no idea what kind of things it could gum up - 2 strokes are not known for a long life and clean combustion. No idea what two stroke oil could do to a valve guide. If you are going to try this, make sure you use an oil that smells good.

 

[RV-9erA]

One thought is to substitute a good brand of 2 cycle oil instead for MMO to use in the fuel. The 2 cycle oil is made to lubricate and also to not foul the spark plugs during combustion.

That's an interesting idea. I use MMO because it was used by the military when they ran piston powered aircraft (mostly to prevent stuck valves). The military purchased MMO by the 50-galon drum, which you can still get from MMO. For me, MMO is about both cleaning combustion byproducts and lubricating the top-end, and it's good for the fuel system. An old A&P IA years ago suggested that I use MMO in my fuel after buying our first airplane and experiencing several suck valves -- that problem went completely away with MMO. I use it in our 2012 Subaru, two restored 70's Honda CB Four motorcycles, lawn mower and in our 20-year flying RV-9A. Really amazing that my lawn mower starts on the first pull even after sitting idle for the winter. There's no doubt that it works in how easily engines start and how smoothly they run! It also keeps the fuel selector from binding over time. Marvels Mystery oil was invented by the same guy who invented the Marvel Schebler carburetor for aircraft -- MMO also keeps the carburetor in better condition!

 

[bjdecker]

I could say that I use a mixture of dissolved unobtainium-247 and Varsol but instead I'd like to revisit the OP, sorry all, @mfleming...

I'm still at a loss to understand the dynamics of how a stuck exhaust valve would manifest as a *rising* EGT + rough running engine and *not* result in a bent pushrod and guide tube and maybe other top-end damage.

Condition 1 -- Valve sticks/binds during the opening phase, this causes the pushrod to bend. This bending also shortens the effective length of the rod, potentially ruptures the guide tube. The valve may now close on its own, and subsequently open again but to a lesser degree due to the shortened pushrod. Resulting signature will be a rough running engine -- not too sure of the EGT as the evacuation of the gasses will be incomplete.

Condition 2 -- Valve sticks/binds during the closing phase. Subsequent combustion events may not happen at all - just the piston drawing in air and also exhaust and then pushing it back out. The signature will be a rapidly falling EGT, and CHT, and a wet-dog-shaking engine.

I'm no Mike Busch, and I rarely stay at a Holiday Inn Express -- maybe I've missed something here. Looking again at the EGT signatures in the OP sure seems like a failed plug -- didn't that happen after you did all the valve work as well? (post #38 -- "The first engine run bummed me out as the engine was rough but that ended up to be a bad spark plug").

Just pondering aloud....sorry.

 

[RV-9erA]

I could say that I use a mixture of dissolved unobtainium-247 and Varsol but instead I'd like to revisit the OP, sorry all, @mfleming...

I'm still at a loss to understand the dynamics of how a stuck exhaust valve would manifest as a *rising* EGT + rough running engine and *not* result in a bent pushrod and guide tube and maybe other top-end damage.

Condition 1 -- Valve sticks/binds during the opening phase, this causes the pushrod to bend. This bending also shortens the effective length of the rod, potentially ruptures the guide tube. The valve may now close on its own, and subsequently open again but to a lesser degree due to the shortened pushrod. Resulting signature will be a rough running engine -- not to sure of the EGT as the evacuation of the gasses will be incomplete.

Condition 2 -- Valve sticks/binds during the closing phase. Subsequent combustion events may not happen at all - just the piston drawing in air and also exhaust and then pushing it back out. The signature will be a rapidly falling EGT, and CHT, and a wet-dog-shaking engine.

I'm no Mike Busch, and I rarely stay at a Holiday Inn Express -- maybe I've missed something here. Looking again at the EGT signatures in the OP sure seems like a failed plug -- didn't that happen after you did all the valve work as well? (post #38 -- "The first engine run bummed me out as the engine was rough but that ended up to be a bad spark plug").

Just pondering aloud....sorry.

A valve starting to not close completely with a nearly total loss of cylinder compression. Don't know about the EGT question but it should drop-off. This is a very common problem that many pilots have experienced without any engine damage -- the picture show how.

 

[bjdecker]

A valve starting to not close completely with a nearly total loss of cylinder compression. Don't know about the EGT question but it should drop-off. This is a very common problem that many pilots have experienced without any engine damage -- the picture show how.

View attachment 88044

FWIW those are intake valves I believe. EGT valve stems look like this.

 

[RV-9erA]

FWIW those are intake valves I believe. EGT valve stems look like this.

View attachment 88053

A sticking valve is generally from crud that builds-up on the valve stem (either intake or exhaust valve). I'm guessing from your post that you have never experienced a suck valve? You're very lucky! I experienced a number of them before using a good fuel and oil additive (MMO and AvBlend). My first stuck valve was during PPL training on my long solo cross-country in 1978 and during my PPL check-ride. I've also had several in my Beechcraft before starting to use MMO and AvBlend, but none since then.

 

[ve0kog]

since we are posting pics..
this is the intake valve on the coldest/leanest cyl. looks like lead to me. #1 looks similar except the build up all black (carbon?)
I was told this isn't necessarily bad. I'm using only Camguard flavoring for the oil, and nothing in the 100LL.

 

[bjdecker]

A sticking valve is generally from crud that builds-up on the valve stem (either intake or exhaust valve). I'm guessing from your post that you have never experienced a suck valve? You're very lucky! I experienced a number of them before using a good fuel and oil additive (MMO and AvBlend). My first stuck valve was during PPL training on my long solo cross-country in 1978 and during my PPL check-ride. I've also had several in my Beechcraft before starting to use MMO and AvBlend, but none since then.

Over a long flying career and ownership, of many different aircraft and engine types, never used a fuel or oil additive, and [thunking forehead] never had a stuck valve. Must be clean living

Now, I have had "wet dog shake" in flight, at cruise and at take off - always traced back to crud in the injection "spider", water in the fuel, or a failed spark plug...

 

[RV-9erA]

since we are posting pics..
this is the intake valve on the coldest/leanest cyl. looks like lead to me. #1 looks similar except the build up all black (carbon?)
I was told this isn't necessarily bad. I'm using only Camguard flavoring for the oil, and nothing in the 100LL.

View attachment 88054

Very nice picture! And, that's it -- as long as this build-up doesn't prevent the valve stem from moving back into it's valve guide -- otherwise, a stuck valve.

 

[sansoneservices]

One thought is to substitute a good brand of 2 cycle oil instead for MMO to use in the fuel. The 2 cycle oil is made to lubricate and also to not foul the spark plugs during combustion.

Any 4 stroke gas engine benefits from a 100:1 mix of premium 2 stroke oil. Automobiles NO because of o2 sensors in the exhaust. Plugs won't foul, premium 2 stroke oil won't gum-up rings or valves at 100:1

 

[RV-9erA]

Over a long flying career and ownership, of many different aircraft and engine types, never used a fuel or oil additive, and [thunking forehead] never had a stuck valve. Must be clean living

Now, I have had "wet dog shake" in flight, at cruise and at take off - always traced back to crud in the injection "spider", water in the fuel, or a failed spark plug...

Well -- the "old timer's" would commonly refer to a stuck valve -- "so you had a shaker", which could happen right after takeoff or in cruise but many times would stop after a short period of uncomfortable shaking.

 

[RV-9erA]

Any 4 stroke gas engine benefits from a 100:1 mix of premium 2 stroke oil. Automobiles NO because of o2 sensors in the exhaust. Plugs won't foul, premium 2 stroke oil won't gum-up rings or valves at 100:1

I've found this to be true using MMO in my fuel too, but it's also worked VERY well without any negative side-effects, including the O2 sensor, in my 2012 Subaru Forester since new even after 145K miles.

 

[olyolson]

I must say -- ever since I started using Marvel's Mystery Oil in my fuel (0.4 oz per gallon) and AvBlend during oil changes with AeroShell 15W-50, my days of stuck valves ended many years ago! Cylinder compression stays high and equal, and borescope pictures inside cylinders look much cleaner along with cleaner sparkplugs. Marvel's Mystery Oil also helps prevent a sticky fuel selector valve. There may be some naysayers out there, but I know it works and has for many years for me! I use it in everything internal combustion motor!

How is using MMO in the fuel different from using Decalin in the fuel?

 

[RV-9erA]

How is using MMO in the fuel different from using Decalin in the fuel?

MMO is not only a mild solvent, but it also lubricates the top-end. I understand that Decalin is more of a solvent used as a paint thinner or paint remover substitute.

 

[sansoneservices]

Last time I checked, years ago, MMO consisted of naptha and gun oil. Neither will cause harm used in moderation.

 

[RV-9erA]

Last time I checked, years ago, MMO consisted of naptha and gun oil. Neither will cause harm used in moderation.

Here's a more detailed breakdown:

• Petroleum Distillates: This is the base component, including mineral oil (60-100%) and Stoddard solvent (10-30%). Stoddard solvent is a type of mineral spirits.
  
  
• Tricresyl Phosphate: Acts as an anti-wear and extreme pressure additive.
  
  
• Ortho-dichlorobenzene: A softening and removing agent for carbon-based contamination.
  
  
• Para-dichlorobenzene: Used as a precursor in polymer production.