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Sticky valve on a Thunderbolt IO390

… and what is the recommended personal intake a day?

It depends Dan. It was a liter on that particular day :D

depends_on_a_day_-_1_(1).jpeg



I assume that ratio 1:300 is Gal MMO:Gal fuel? Da, Nyet?

Да Джеф :D
 
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yeah Vlad, I think we had just the right amount of MMO that day, no sticking valve at all :D

PS
And a day I’ll sure never forget…
 
Original (210 hp) or the exp (215 hp)

Does anyone think this could be related to the newer version and setup? My 390 (210 hp version) also shows #2 cylinder 20 F hotter than the rest.
 
It seems #2 runs hotter on all 14's but all CHT's are much cooler than most engines. MY #2 is also the hottest but has never been over 345F. I don't get why #2 should be an issue.
 
Vlad, sorry, thread drift.
How do you protect the LE on your hor stab on those gravel runways?
Thanks
 
Rehab on sticking valve - IO390

I'll begin with a summary:
My engine is a Lycoming IO-390 - Thunderbolt build. At 270 hours in October 2021, I experience a sticking exhaust valve on cylinder 2. The valve was so tight, that it required tapping out to release it. I reamed the valve guide yielding a black semi-hard tar/coke material. No wobble test was performed, and nothing was done to other cylinders. Returned to service and normal operation.

Just before this incident, I had installed the Tunnel Cooling Flap kit designed for the EXP-119 engine on RV-14s. My plane has a Vetterman trombone exhaust (2 x 2-into-1), meaning the tunnel is empty providing addition cowl exit area and even greater cooling than a stock setup. While I was installing it in the quest for speed/efficiency, it became a good way to increase engine temps in an attempt to reduce valve guide buildups (following the Camguard and Mike Busch school's of thinking).

At 396 hours (125 since last incident), I again experienced a sticking exhaust valve, again on cylinder #2 on 2 days. Day 1 involved "morning sickness" for 30 seconds prior to a normal flight with 2 segments, an hour each. On Day 2, morning sickness occurred again, for about 45 seconds. After a normal run-up (with CHTs all over 250), I took off and had cylinder #2 drop out for 6 seconds on climb out, followed by 45 minutes of normal operation.

Now - the update to the story:
Lycoming Technical Service spent about 40 minutes on the phone with me, but every idea for a cause was a dead end - they are stumped.
1. too cool? - except I increase CHTs with the tunnel cooling flap and "harder" operations, and cylinder #2 runs 350 in cruise, a good number.
2. dirty oil? - I change every 40 hours, and my silicon reading is very low
3. slow flight operation (cool and low power)? - I don't do this
4. glazed cylinder with excess oil going to valve? - 78/80 on all cylinders

Lycoming recommendations:
1. SB 388 C (wobble test) on all cylinders
2. SI 1425A - ream valve guides on all cylinders
forward results to Tech Service

To perform the infamous wobble test, you need fixture (ST310 for angle valve) which Lycoming will rent to you. This process is really tedious - I had to call a Lyc distributor (Aircraft Spruce) who called Lycoming to verify the tool is available, and it then drop ships from Lycoming. The rental for 30 days is a somewhat reasonable $100, but Lycoming also requires a $4,600 deposit before shipping (they REALLY want it back - refunded on return). It took a week to get the tool. You can buy an alternate tool from ACS for <$300, but it is out of stock until January, so I went with the rental. Before the rental tool fixture arrived, I was able to borrow the ACS tool (made by Sydow) from a neighbor, and in my hands, the ACS/Sydow version was superior to use.

The wobble test SB 388C measures the "lateral play" end to end in the valve guide. I believe the idea is that too little play and differential expansion rates will cause binding (morning sickness until everything warms up, and again under high load such as climb out). Too much play and there is excess room for deposits and contaminants to build up. For an angle value, the acceptable wobble is 0.015 to 0.030". To perform the measurement, an extension is fastened to the end of the valve stem, with the extension displaced in opposite directions by prying against the case, and the differential measured, either with feeler gauges against a set screw or with a micrometer gauge. My good cylinders were .020 and .022" with the faulty #2 only 0.012".

Next comes SI 1425A for reaming the valve guides. The valve springs have to be removed (this was done before the SB388C), and the valve pushed into the cylinder. A reamer is greased (to catch debris) and fed into the guide. A clean guide will accept the reamer with only hand forces - this was true of my cylinders #1 and #4. Valve guides with buildup with require more force - either a hand tool on the reamer or in my case, I used a power drill at very slow speed. Cylinder #3 had minor buildup (a trace of black coke on the bit) and a coating on the valve stem that cleaned off with acetone and scotchbrite. Cylinder #2 (the problem child) had a clean valve stem but more significant coking in the guide. After reaming, the wobble test was 0.018" - still my tightest but close to the rest. After all the reaming, the valves have to be fished back into the guide (a tricky endeavor), the springs and keepers reinstalled, pushrods and shrouds put back if removed, and rockers, covers etc. put back.

The plane is back in the air - two flight days with normal operations. I have asked Lycoming about using CamGuard additive in the oil (captures monomers that form varnish) and TCP fuel additive that scavenges lead.

I will post some pictures in a separate post for those interested.

Let the ideas and suggestions start ...
 
Pics to accompany prior post

Some pictures:
Pic 1: Exhaust valve stem #3 - with a buildup
Image_2022-11-07 16_25_39_345.JPG
Pic 2: and after clean up
Image_2022-11-07 16_37_30_678.JPG
Pic 3: Reamer after cylinder #2 (note: brown is grease to capture contaminants)
Image_2022-11-09 11_18_21_005.JPG
Pic 4: From valve guide
Image_2022-11-09 11_19_41_224.JPG
 
Thanks for your report Keith.
It matches exactly all the cases of sticking valves as found and experienced by many, and myself, on other engines such as 360s, 320s, etc.

This sticking valve problem has been ongoing, probably since last century when these engine started being produced. Even using the latest hi-chrome guides…
No single cause, or reason, has been identified to date. Run it hot, cold, reach or lean, Camguard or not, this oil or the other one, miracle additive or not, we have had sticking valves…

Having had a sticking valve in flight that led to an emergency landing on a military base taught me to never ever take-off with an engine showing any sign of sticking valve. A sticking valve can lead to the destruction of the engine.
 
What are the specific symptoms of a sticky valve on start up other than the general description of "morning sickness"? Does anything show up on the EGT's? Do they stick open or closed or either? Would pulling the prop through prior to start up show a stuck valve being open resulting in no compression?
 
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Go to the first post in this thread. There is also a pic of what the data looks like in post 21.

I will post a screen shot later of the specific instance mentioned in the first post.
 
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What are the specific symptoms of s sticky valve on start up other than the general description of "morning sickness"? Does anything show up on the EGT's? Do they stick open or closed or either? Would pulling the prop through prior to start up show a stuck valve being open resulting in no compression?

Generally a valve will stick open. If it sticks closed, the pushrod bends and it never fully opens again. If an exhaust valve sticks fully or partially open, CHTs and EGTs will drop. Magnitude of drop based upon how far open they are sticking.

Larry
 
Higher or lower CHT's?

I've been following this thread as I was going to cover my tunnel since I have the Vetterman's 4 into 2 muffler and fairly easy to do. It "seems" from limited data cylinder #2 at least for the 390 appears to have the sticky valve issue and it is the hottest cylinder on 90% of the 390's being run in the fleet. From this data it seems that heat might be an issue and if that is true decreasing the airflow around the cylinders might be something that should not be done. I would hate to gain 2 - 3 knots and go through a stuck valve in the future. When it comes to engine design and understanding I really do not know enough to even phrase this question correctly buy would love for someone to weigh in on this.
 
I've been following this thread as I was going to cover my tunnel since I have the Vetterman's 4 into 2 muffler and fairly easy to do. It "seems" from limited data cylinder #2 at least for the 390 appears to have the sticky valve issue and it is the hottest cylinder on 90% of the 390's being run in the fleet. From this data it seems that heat might be an issue and if that is true decreasing the airflow around the cylinders might be something that should not be done. I would hate to gain 2 - 3 knots and go through a stuck valve in the future. When it comes to engine design and understanding I really do not know enough to even phrase this question correctly buy would love for someone to weigh in on this.

It would be interesting to know if most of the stuck valves to date have occurred in -14's with or without the tunnel flap. What I mentioned earlier is I don't understand why #2 is the issue as most data I have seen is yes #2 is warmer but still much cooler than most other Lycoming engines that I have flown. 390's seem to run warm oil and cooler CHT's.
 
Got this today:

The Savvy analytics team is developing a screening model for early detection of sticking exhaust valves. If you think you have experienced a stuck exhaust valve in any phase of flight, we would love to review your engine monitor data to help develop our models. If you're interested in sharing your data, please send a note to Adam Goler. (Firstname dot Lastname at savvyaviation dot com)

You need not be a subscriber to any of Savvy's services to participate. Thank you!
 
It would be interesting to know if most of the stuck valves to date have occurred in -14's with or without the tunnel flap. What I mentioned earlier is I don't understand why #2 is the issue as most data I have seen is yes #2 is warmer but still much cooler than most other Lycoming engines that I have flown. 390's seem to run warm oil and cooler CHT's.

Glenn,

I have a Thunderbolt IO390 on a 14 built to plans without tunnel flap. After fixing my sticking, I switched from phillips 20/50 to W100 plus and am trying 25 hour oil changes. I don’t see this engine as too warm.

Will chime in at next instance.

I have communicated with Adam/Savvy - they have all my data already.
 
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Hard to ground it, but too many bad things can happen.

Would pulling the prop through prior to start up show a stuck valve being open resulting in no compression?


Yes, and you should immediately ground the airplane and fix the problem.

The valve might be closed when shut down, but after cooling, it would stick open slightly. The piston will push it close, but not closed.

Hoping it will be ok is not a good plan forward.
 
One thing to try.

Dennis,

By-passing air on the front of #2 around that casting flash and zero fin depth is the best, but not the only way to effect some improvement. I made the chute on my 7, but my 10 friend was already flying and did not want to tear into the baffles. A sticker for data, he drilled 5 holes aligned with the fin channels in the cross angle that holds the baffles. I think they were #30 drill size. He found a 10-15 deg reduction in the CHT as a result. The holes were located in the root radius and opened into the gap below. At about 30 deg off vertical. He now has over 600 hrs and no adverse structural effects from the holes.

You would be surprised how much air will go through a #30 hole at 12-15" of air pressure. When I was doing pressure testing of my plenum and swapping hoses, The flow through a 3mm tube was enough to cool my face in the cabin. And that was 4 ft of tubing with associated vicious losses.
 
Stuck valve or ignition?

Following this thread closely. I have a IO360 with a mag on the lower plugs and a Lightspeed electronic ignition on the upper plugs. The engine displays the symptoms of "morning sickness" as described. Number 3 cylinder egt is about 250 degrees below normal but the engine runs smoothly with both ignitions on. A different wrinkle is that my engine runs smoothly if I turn off the mag and run the engine only on the Lightspeed. It runs rough on mag only but still low egt only on cyl 3. It smooths out on the mag if I aggressively lean during runup.
My conclusion is that it is an ignition problem not a stuck valve. Wishful thinking?

Ted
RV4
 
It smooths out on the mag if I aggressively lean during runup.
My conclusion is that it is an ignition problem not a stuck valve. Wishful thinking?

Ted
RV4

This kind of points to a fuel/mixture issue, though could be ignition. rough running due to a sticking valve cannot be resolved with ignition or mixture changes. Not enough detail here to give guidance. Morning sickness typically presents as rough running for several minutes until things warm up and then the valve becomes un-stuck and performs normally. However, not all stuck valves will present with morning sickness. If you want to give a more detailed description of the symptoms, we can possibly give more guidance.

Low egt could be too rich, too lean, too advanced on ignition, compression loss due to several factors, including valve issues, etc. If you can make it go away with ignition changes, the most likely issue is mixture or advance.
 
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Thanks for the reply. Since the engine is running smoothly on the electronic ignition, and it appears to be just one cylinder that is affected, I am concentrating on the magneto and the spark plugs. I am thinking a fouled plug on #3 cylinder. I'm still not sure if a fouled bottom plug would cause the low EGT reading, however. Will find out when I replace the plugs.

Ted
RV4
 
Spark plug resistance test.

Measure with a digital ohm meter. Both Champion & Tempest say to replace spark plugs that have more than 5,000 Ohms resistance. I recently replaced a Tempest Iridium plug that had almost 10,000 Ohms resistance & was causing the engine to run rough on that magneto. Using my EGT it was easy to tell which cylinder the bad plug was in. There is a good TouTube video on how to do this. I verified the spark plug was mis-firing when tested in a spark plug tester under pressure.
 
On our airport E16 (San Martin) in Kalifornia we only have UL94. The engine in my Cub runs so much better without the lead. Plugs look great at annual. Lead deposits on piston tops is dissipating. Compression is more even.

Has any one tried unleaded in their 390’s to try to eliminate valve sticking?
 
Thanks for the reply. Since the engine is running smoothly on the electronic ignition, and it appears to be just one cylinder that is affected, I am concentrating on the magneto and the spark plugs. I am thinking a fouled plug on #3 cylinder. I'm still not sure if a fouled bottom plug would cause the low EGT reading, however. Will find out when I replace the plugs.

Ted
RV4

When you go from 2 plugs firing to one plug firing, it lowers the effective timing advance (i.e. retarded) and your EGTs will go up (in the range of 150-200 though this varies a lot based upon the advance setting of each ignition) not down and CHTs will drop a small to moderate amount. Generally speaking, More advance = lower EGT / higher CHT. Less advance = higher EGT / lower CHT. When both EGT AND CHT drop, ignition becomes low probability as the source, assuming neither drops to VERY LOW levels. Compression and Mixture are where you look as well as valve isssues.
 
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On our airport E16 (San Martin) in Kalifornia we only have UL94. The engine in my Cub runs so much better without the lead. Plugs look great at annual. Lead deposits on piston tops is dissipating. Compression is more even.

Has any one tried unleaded in their 390’s to try to eliminate valve sticking?

I’m building mine so that it’s 100% unleaded MOGAS compatible….both with and without ethanol. I want to avoid the lead deposits from the beginning. I have my -8 setup like this and she’s never missed a beat.
 
I’m building mine so that it’s 100% unleaded MOGAS compatible….both with and without ethanol. I want to avoid the lead deposits from the beginning. I have my -8 setup like this and she’s never missed a beat.

How are you building yours to be 100% unleaded MOGAS compatible?
 
1. Reamer is not a good tool for the job as the guides wear oblong in opposing directions at each end. A reamer will not get all of the deposits out if there is considerable guide wear. Ball hone works better, cheaper, easier to use

I noticed that the reamer did alright, but as Bob describes there is still some deposit material at the ends of the guides.

Trying to select the correct hone for this job. Looks like aluminum oxide is the right abrasive for the guide metal, but what grit should be used? According to this write-up, 240 grit would be used for the final finish:

http://www.guy-croft.com/viewtopic.php?f=2&t=949

Correct hone?

https://www.amazon.com/dp/B007INRL0O/ref=twister_B09D951TJB?_encoding=UTF8&th=1
 
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In case anyone wants to hone their guides, I received the following from tech support at Brush Research:

Thank you for your inquiry!

To clean a bronze valve guide, we would suggest using Aluminum Oxide and our 240 grit.

Our 240 grit works well for general purpose deglazing, putting in a cross-hatch, and seating rings.
Our Aluminum Oxide abrasive type is typically recommended for base materials of aluminum, bronze, brass, and softer metals.
 
I've reamed quite a bit of valve guides over the years... and not sure I'd use a hone.
The cause of valve sticking is the build up at the edge of the combustion chamber on this side of the guide. Only. The problem with a hone is the "removal" of material on the whole length of the guide, when one is looking only to remove the offending stuff.

A little bit of grease on the reamer. Adjusted to the minimum to scrape off the built-up crud. Then position the stem of the valve thru the bottom plug hole to clean its stem. Re-install.
 
Absolutely Jon. I've read Bob's advice, and he is correct when he states:

A reamer will not get all of the deposits out if there is considerable guide wear.

If there is considerable guide wear...
I have to admit never having used a hone since the reamer always worked for me.
The hone has two pros, the price (compared to an adjustable reamer), and the ease of use. Using a reamer, one has to be very careful on the adjustment lest damage to the guide could occur.
 
We had great success with marvel mystery oil mixed with the gas on our piston helicopters in the south Texas high heat. Never had a push rod exit the valve cover while using Marvel but we sure did when we didn't.
 
I'm making some (slow) progress on cleaning the valve guides, but am wondering about cleaning the valve stems. They have very hard deposits on them that I'd like to remove completely before reinstalling them. What's the best way to clean the stems? I'm using a no-scratch pad, but is there a safe solvent I can use? I've read Marvel Mystery Oil will help dissolve these deposits. What else will work while I have access to the valve stems? - Thanks
 
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I'm making some (slow) progress on cleaning the valve guides, but am wondering about cleaning the valve stems. They have very hard deposits on them that I'd like to remove completely before reinstalling them. What's the best way to clean the stems? I'm using a no-scratch pad, but is there a safe solvent I can use? I've read Marvel Mystery Oil will help dissolve these deposits. What else will work while I have access to the valve stems? - Thanks

Red scotchbrite,
 
However, not all stuck valves will present with morning sickness.

This is an important point. My symptoms would only come on at altitude after 20 minutes of flying. There are plenty of accounts of this happening at cruise, ie, not immediately after cold engine startup, so it's best not to assume you will get that warning on the ground. I've since reamed the guides and honed them, and scrubbed the valve stems clean. 10 or so hours in and the problem has not resurfaced, though it does shake one's confidence in the powerplant, so I'm staying close to the airport for awhile. Having gone through more than one episode of this, I will say that it is quite dangerous, and very scary. From here out, I'm going to drop the exhaust and perform the cleanup process once a year.
 
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Another sticking valve

Another update with a problematic IO390 (Thunderbolt). Brief recap, I experienced my first sticking valve around 270 hours, combination of inflight symptoms and morning sickness. Reamed the culprit (cyl #2). Second incidence was around 395 hours (delta 125 - bad trend), again on cyl #2. I reamed all exhaust guides including performing wobble measurements. Found coking on 2 cylinders, but only #2 was below wobble specs (before reaming - within spec after). As preventative treatment (gotta try something), I added Camguard to my oil, installed the tunnel cooling flap to increase operating temps, and began cruising at higher power settings.

This month was my annual, about 50 hours since last valve treatment. I decided to proactively ream the guide on cyl #2 even though I had no symptoms, hoping that I might get to an annual preventative treatment rather than reacting to a sticking valve. I was disappointed to find the same amount of coking on cyl#2 valve guide after only 50 hours - well, not quite the same amount since symptoms hadn’t started yet.

My next reaming will occur at the earliest of 1) next annual at 120-150 more hours or 2) reoccurrence of sticking valve symptoms. Total time on the engine is now about 450 hours.
 
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Another update with a problematic IO390 (Thunderbolt). Brief recap, I experienced my first sticking valve around 250 hours, combination of inflight symptoms and morning sickness. Reamed the culprit (cyl #2). Second incidence was around 380 hours (delta 130 - bad trend), again on cyl #2. I reamed all exhaust guides including performing wobble measurements. Found coking on 2 cylinders, but only #2 was below wobble specs (before reaming - within spec after). As preventative treatment (gotta try something), I added Camguard to my oil, installed the tunnel cooling flap to increase operating temps, and began cruising at higher power settings.

This month was my annual, about 50 hours since last valve treatment. I decided to proactively ream the guide on cyl #2 even though I had no symptoms, hoping that I might get to an annual preventative treatment rather than reacting to a sticking valve. I was disappointed to find the same amount of coking on cyl#2 valve guide after only 50 hours - well, not quite the same amount since symptoms hadn’t started yet.

My next reaming will occur at the earliest of 1) next annual at 120-150 more hours or 2) reoccurrence of sticking valve symptoms. Total time on the engine is now about 450 hours.

Just curious has anyone talked with Lycoming and have they offered any thoughts?
My first 14A has about 300 hours now and my current 14A just pass 120 without any such symptoms.
 
As preventative treatment (gotta try something), I added Camguard to my oil, installed the tunnel cooling flap to increase operating temps, and began cruising at higher power settings.

This month was my annual, about 50 hours since last valve treatment. I decided to proactively ream the guide on cyl #2 even though I had no symptoms, hoping that I might get to an annual preventative treatment rather than reacting to a sticking valve. I was disappointed to find the same amount of coking on cyl#2 valve guide after only 50 hours - well, not quite the same amount since symptoms hadn’t started yet.

Just as a point of reference, I've always had very cool CHT's (320-340 avg, 375 is rare on a hot day hard climb) and generally operate 50 ROP EGT (1375 ish), never had a stuck valve. Maybe just lucky?
 
Just as a point of reference, I've always had very cool CHT's (320-340 avg, 375 is rare on a hot day hard climb) and generally operate 50 ROP EGT (1375 ish), never had a stuck valve. Maybe just lucky?

I have over 1400 hours / 20+ years on my engine, operated in all kinds of temperatures and conditions, and never had one until recently.
 
CHT high or lower is better

I’ve read from our forum engine expert that we need higher temperatures to combat “sticky” valves but if that is accurate why does it seem that in the majority of cases it’s cylinder 2 that develops this issue and that cylinder has the highest temps ? Shouldn’t our cylinders with the coldest CHT’s develop sticky valves first ?
 
My IO-360 angle-valve developed a sticky exhaust valve on #4, which is always the coldest one for me (typ 350 or less). That was with 800-ish hours on ECI-rebuilt cylinders (original Lycs with all new replaceable parts and nickel-carbide on the cyls). The wobble clearance was about 0.003" less than minimum, so hardly "stuck". Cleaned up with a hone.
 
390 Angle valve

Since this thread I thought was for angle valve 390's (See initial post) my comments where for this particular engine. I believe every sticky valve reported for a 390 was cylinder 2. (And the hottest cylinder) Obviously with this engine oil squirters are also used so maybe this might be a difference?
 
I’ve read from our forum engine expert that we need higher temperatures to combat “sticky” valves but if that is accurate why does it seem that in the majority of cases it’s cylinder 2 that develops this issue and that cylinder has the highest temps ? Shouldn’t our cylinders with the coldest CHT’s develop sticky valves first ?

Unfortunately there is NO definitive research to tell us what is causing the build up in the guides and / or what conditions encourage or discourage it. It is still a mystery. Unfortunately that doesn't stop guys like Mike B from stating opinions as fact and offering a solution. I am convinced it is due to heat in the exh valve due to oil starvation. But that is just my opinion - completely unsubstantiated. I think I have read at least 5 different opinions for the cause. I fly a lot in the winter where CHT are well under 300. I did a wobble test and all the guides were on the loose side, so absolutely 0 deposits.
 
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Angle valve design ??

Is there something about angle valves or angle valve with oil squirters that make this engine unique? Seems most of the Vans fleet uses parallel valve engines (360's and 540's) and those are random or maybe squed toward the cold cylinder side but their does seem to be a pattern with the 390 and cylinder #2 getting sticky and this runs far and away hotter than the others. (I've completely removed my air dam in front of the cylinder early on to help reduce the temperatures on 2, still 20 - 25 F hotter than the rest) One thing that does seem to be different in the angle valve 390 compared to the parallel valve is the oil seems to get dirty very quickly. I was taught to change the oil on condition and at 20 - 25 hours my oil is pretty black and change it. The 390 also seems to burn oil at a higher rate than the 360. I'm lucky to get 8 hours a qt and I know others who are getting 5 hours a qt. As Mike says seems the engine is telling us something, now to figure out what it is saying.
 
Shouldn’t our cylinders with the coldest CHT’s develop sticky valves first ?

Upon taking the valves out, my findings were that my #3 cylinder, which I'm pretty sure is the hottest of the 4, was the one that had by far the most deposits on the value stem. In fact the other 3 had little if any deposits on the valve stem. Could be coincidental, but it appears the hotter cylinders are more susceptible. Might also be a lot of high/low temp fluctuations that brings this on.
 
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