Ahhh, interesting. I never see valves stick in the closed position on automotive engines. I hadn't considered that scenario.
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Superior cylinder rocker boss failure
- Thread starter Greg Arehart
- Start date
Ahhh, interesting. I never see valves stick in the closed position on automotive engines. I hadn't considered that scenario.
Greg Arehart
Well Known Member
For the record, I measured the pushrod deflection in the bent exhaust rod, and it is somewhere between 1/32 and 1/16.
Today we tested the valves. First test was just pushing on the valves with springs etc. in place. Both valves moved with about the same amount of pressure, although the exhaust valve had a bit of a detent at the start. No other evidence of dragging that we could tell.
We then pulled the valves off. Exhaust valve did not drop into the cylinder as the intake valve did, but a light tap with a hammer and it dropped. Exhaust valve diameter measured 0.001 below ideal, but still within spec. The thought is that this is normal (?) wear. Exhaust valve guide was checked with (I'm not an engine guy so bear with me) a standard gauge. My understanding of this is that the valve guide is slightly tapered and the depth that the gauge can be inserted tells something about the internal diameter of the guide. Anyway, the gauge went in about 1/2 inch rather than the 2.5 inches that it should have. This could be a couple things: 1) the guide was undersized to begin with, or 2) there are carbon or other deposits in there choking the guide. There are no obvious carbon or lead deposits anywhere in the cylinder (consistent with running a lot of mogas through the system). There is no obvious belling of the cylinder end of the guide.
The sense of the mechanics here was that maybe this was a bit of a "sticky" valve, but it was not a "stuck" valve. I'll note for the record that I have seen no "morning sickness" prior to this incident. I don't have a feel for whether the valve would be more sticky at high temperature or less sticky, and the role that that might have played in the failure.
Compressing the valve springs to remove valve (courtesy Bob Mills iPhone):
Interior of the cylinder (also courtesy of Bob):
So all this still leaves me wondering what happened. I will reiterate that the first sign of problems was an engine cough, a couple seconds of smooth, followed by a second (longer) cough and then the engine running rough. I first touched mixture and throttle only after the first cough thinking that I might have a fouled plug. I am used to flying out of 5000-foot RTS where it is easy to foul plugs if one runs too rich. Dynon indicates that I was at ~3600 feet at that time.
Another bit of perhaps useful data: at this altitude, my peak EGTs would typically be over 1500, so I was still on the rich side of peak EGT.
With regard to Bob's question of whether I pulled throttle or leaned first, I honestly don't recall, but suspect that I pulled mixture first as indicated by the Dynon data.
Soooo... still looking for answers. Nothing is particularly obvious, at least to me. Maybe a stuck valve, but if it wasn't a stuck valve, what was it? [after attending the AOPA safety seminar last night, the most probable answer for almost anything seems to be "pilot error" but if that is the case, I would like to know my error to avoid it in the future - perhaps the most likely error was, as Dan indicated, the wrong amount of leaning]
Bob, feel free to add your thoughts from today.
Cheers,
greg
Today we tested the valves. First test was just pushing on the valves with springs etc. in place. Both valves moved with about the same amount of pressure, although the exhaust valve had a bit of a detent at the start. No other evidence of dragging that we could tell.
We then pulled the valves off. Exhaust valve did not drop into the cylinder as the intake valve did, but a light tap with a hammer and it dropped. Exhaust valve diameter measured 0.001 below ideal, but still within spec. The thought is that this is normal (?) wear. Exhaust valve guide was checked with (I'm not an engine guy so bear with me) a standard gauge. My understanding of this is that the valve guide is slightly tapered and the depth that the gauge can be inserted tells something about the internal diameter of the guide. Anyway, the gauge went in about 1/2 inch rather than the 2.5 inches that it should have. This could be a couple things: 1) the guide was undersized to begin with, or 2) there are carbon or other deposits in there choking the guide. There are no obvious carbon or lead deposits anywhere in the cylinder (consistent with running a lot of mogas through the system). There is no obvious belling of the cylinder end of the guide.
The sense of the mechanics here was that maybe this was a bit of a "sticky" valve, but it was not a "stuck" valve. I'll note for the record that I have seen no "morning sickness" prior to this incident. I don't have a feel for whether the valve would be more sticky at high temperature or less sticky, and the role that that might have played in the failure.
Compressing the valve springs to remove valve (courtesy Bob Mills iPhone):
Interior of the cylinder (also courtesy of Bob):
So all this still leaves me wondering what happened. I will reiterate that the first sign of problems was an engine cough, a couple seconds of smooth, followed by a second (longer) cough and then the engine running rough. I first touched mixture and throttle only after the first cough thinking that I might have a fouled plug. I am used to flying out of 5000-foot RTS where it is easy to foul plugs if one runs too rich. Dynon indicates that I was at ~3600 feet at that time.
Another bit of perhaps useful data: at this altitude, my peak EGTs would typically be over 1500, so I was still on the rich side of peak EGT.
With regard to Bob's question of whether I pulled throttle or leaned first, I honestly don't recall, but suspect that I pulled mixture first as indicated by the Dynon data.
Soooo... still looking for answers. Nothing is particularly obvious, at least to me. Maybe a stuck valve, but if it wasn't a stuck valve, what was it? [after attending the AOPA safety seminar last night, the most probable answer for almost anything seems to be "pilot error" but if that is the case, I would like to know my error to avoid it in the future - perhaps the most likely error was, as Dan indicated, the wrong amount of leaning]
Bob, feel free to add your thoughts from today.
Cheers,
greg
rvmills
Well Known Member
As Greg described, we brought the cylinder over to a local engine rebuild shop, and the shop's "cylinder guy" worked with us.
First we tested the valve movement by setting the cylinder on the floor, and pushing with a wood stick on the top of the stem/spring. As Greg said, both valves moved, but the exhaust valve had a little stick to it as it first moved.
Then we removed the springs...an interesting task with no rocker arm shaft. The pic above was the second interation of adapt and overcome (the cylinder guy is a Marine). The intake valve dropped through its guide, and the exhaust valve did not. I thought it took more than a little tap...actually took a couple...but he did say it was not nearly as hard to pop out as many stuck valves he's had to pound out. So it wasn't stuck hard at the 45 or so degrees in the shop. Would it be much harder stuck at 400, 600 or 1000 degrees? Hard to say, but conventional wisdom says it would be much tighter at operational temperature.
After measuring the stem (.001 under, with a .002 under limit) I felt the stem, and it had a tiny burr in one spot, but we discussed this, and there is no way to tell if it was there before the failure, or was caused by the failure. Our AI bud thought it was too small to be significant, but I mention it, just FYI.
Then the cylinder mech used the "no-go tool" on the guide. It looks like a valve stem, and one end should fit in the guide, while the other should not. The big end did not fit in either end of the guide, so the guide was not worn past limits (makes sense).
When testing with the small end, from the combustion chamber side, he was barely able to put it in the guide, I thought maybe 1/4 inch..should have gone a couple inches in...like Greg said. On the rocker arm side, the no-go tool penetrated over an inch and a half.
From the article linked earlier and our discussion today, guides normally show wear just opposite of what was seen here...the combustion chamber side gets larger, and thats how corrosion and deposits form in there, leading to a sticky valve. There are some deposits in the valve seat area (the pocket the valve head fits in) as you can see from the pic, and some grunge around the end of the valve guide, but that grunge came off when I wiped the end of the guide with my finger. Couldn't tell if there were visible deposits in the guide itself (not sure once could visibly see that, since the tolerances are so tight...I just don't know what to look for).
The cylinder mech said he thought the guide might be tapered incorrectly, but again, is that how it was before the failure, or did the failure tweak it? Or is it just deposits on the hot side of the guide that tightened up the space? Lots of questions remain.
The post-exam convesation focused on whether the valve would have been stuck hard enough at temperature to cause the bent push rod and the failed bosses. We also wonder why the push rod didn't bend further, and the bosses failed instead.
Some opinions only: The engine shop owner and the AI both feel it was a bad casting. However, the AI has talked with friends at the FSDO, NTSB, and at several engine shops, and none of those that he talked with had heard of this failure on these particular cylinders. All are aware that many are watching this thread, and no one wants to bad-mouth the cylinders or cause a fear that this is in any way systemic. Again...important to note...opinions only.
Greg is faced with the decision to replace the other 3 cylinders, or fly these. Knowing that these cylinders have close serial numbers adds to his concern, but the fact that this brand of cylinder has a very large sample group with a very large number of hours on them, and this is a rare failure (perhaps the first for this particular cylinder) perhaps mitigates that concern somewhat.
We've all discussed further inspections, and would like to get a better look at the cam lobe and lifter from that valve, as we didn't get a good look at it in Jean that day. But I know Greg would like to do the due diligence on this, as he's a mountain flyer, and a careful guy. I saw the concern in his face as we talked this out, so I know he'd like to hear further discussion and feedback.
And Dan, in discussing the leaning process that day, it sounds like (my interpretation) that when the engine coughed, he thought he was perhaps on the rich side, so he leaned a bit to see if it smoothed out...no major pulls on the red knob. From the graph, after that, it looked like he may have pulled, then added a little throttle, and that cylinder did a quick dead cat bounce, then gave up the ghost (red EGT line to zero). All FWIW, and just one possible interpretation of the graphs.
Still think Greg did a helluva job that day, in decision making and flying!!
Cheers,
Bob
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frazitl
Well Known Member
I would be interested in the wobble test
on the failed cylinder (and the rest too). As I recall, the test has a lower AND upper limit of valve wobble that is acceptable. Whether from too tight metal clearances, or carbon build-up, an under limit valve wobble calls for reaming the guides to spec.
The tight valve off the seat that you felt is the same thing I felt. Speculating here, but on take off as the engine heats up, I would expect the valve stem to grow in OD faster that the valve guide ID grows. Thus, a stuck valve and a bent push rod.
Please continue your search for the root cause. My engine failure experience (Continental TSIO360 in a Mooney 231 - totaled
) taught me to not give up until I understood at least one plausible explanation for root cause of the failure.
on the failed cylinder (and the rest too). As I recall, the test has a lower AND upper limit of valve wobble that is acceptable. Whether from too tight metal clearances, or carbon build-up, an under limit valve wobble calls for reaming the guides to spec.
The tight valve off the seat that you felt is the same thing I felt. Speculating here, but on take off as the engine heats up, I would expect the valve stem to grow in OD faster that the valve guide ID grows. Thus, a stuck valve and a bent push rod.
Please continue your search for the root cause. My engine failure experience (Continental TSIO360 in a Mooney 231 - totaled
) taught me to not give up until I understood at least one plausible explanation for root cause of the failure.Captain Avgas
Well Known Member
Question for John Schwaner
Hi there John, thank you for your professional contribution to this thread.
However I'd appreciate it if you could clarify something for me.
in the following Avweb article written by you and referred to in Post #84 in this thread http://www.avweb.com/news/maint/182894-1.html you state as follows: "Lycoming valve stems operate at higher temperatures than Continental valves stems".
However in the Sky Ranch Engineering Manual, also written by you, you state on page 212 (fig 4-4) as follows: "Lycoming valve design results in lower valve temperatures due to increased coefficient of conductivity provided by the sodium. Notice how Lycoming allows a portion of the guide to stick out beyond the guide boss. This helps keep the valve cool by shielding the valve stem from hot combustion gasses."
I guess I'm a bit confused about this. If the Lycoming sodium filled valve design with its protruding guide has improved cooling features over the Continental solid valve design as you state in the Sky Ranch Manual then why does it run hotter than the Continental as you state in the Avweb article?? Can you clarify this issue.
Hi there John, thank you for your professional contribution to this thread.
However I'd appreciate it if you could clarify something for me.
in the following Avweb article written by you and referred to in Post #84 in this thread http://www.avweb.com/news/maint/182894-1.html you state as follows: "Lycoming valve stems operate at higher temperatures than Continental valves stems".
However in the Sky Ranch Engineering Manual, also written by you, you state on page 212 (fig 4-4) as follows: "Lycoming valve design results in lower valve temperatures due to increased coefficient of conductivity provided by the sodium. Notice how Lycoming allows a portion of the guide to stick out beyond the guide boss. This helps keep the valve cool by shielding the valve stem from hot combustion gasses."
I guess I'm a bit confused about this. If the Lycoming sodium filled valve design with its protruding guide has improved cooling features over the Continental solid valve design as you state in the Sky Ranch Manual then why does it run hotter than the Continental as you state in the Avweb article?? Can you clarify this issue.
john.schwaner
Member
Bob,
It's my sloppy writing. Notice in the first quote I state "valve stems." Place an emphasis on stems. The second quote should state "valve head." Lycoming conducts the heat from the head into the stem thereby cooling the head but heating the stem. The Continental exhaust valve transfers heat only through the sealing surface so the head is hotter and the stem cooler. You can see this in the picture below.
From the photograph above how the heat signature is further up the stem on the sodium cooled Lycoming valve than on the Continental valve.
We noticed back in the 1980's that there were much much more valve sticking on Lycoming engines than on Continental engines. At the time Lycoming blamed valve sticking on the pilot; which led to my joke about Continental pilots being better than Lycoming pilots. A dubious proposition indeed!
I also challenged any pilot to purposely create valve sticking by operating the engine in some way. So far none of the "its the pilot's fault crowd" can meet the challenge. So valve sticking appears not to be caused by the pilot.
We also noticed that when the valve ran hotter than normal (because of valve leakage) that there was more sticking. We then concluded that the reason Lycoming exhaust valves stick more than Continental was because the Lycoming valve stem is hotter.
This is a quote from an article I wrote in 2009
"If the valve sticks closed and doesn't open in 1/2 propeller revolution the rocker arm supports will blow-off leading to total loss of engine power."
[article link]
The reason the rocker boss supports blow is that when the exhaust valve doesn't open the gas is not released and creates very high pressures that hold the intake valve closed. When the intake rocker arm tries to open the valve it doesn't budge and something has to give. The rocker boss at the intake fractures. You see this on the Continental O-200 because the rocker boss supports on older style cylinders are thin and rather frail.
It's my sloppy writing. Notice in the first quote I state "valve stems." Place an emphasis on stems. The second quote should state "valve head." Lycoming conducts the heat from the head into the stem thereby cooling the head but heating the stem. The Continental exhaust valve transfers heat only through the sealing surface so the head is hotter and the stem cooler. You can see this in the picture below.
From the photograph above how the heat signature is further up the stem on the sodium cooled Lycoming valve than on the Continental valve.
We noticed back in the 1980's that there were much much more valve sticking on Lycoming engines than on Continental engines. At the time Lycoming blamed valve sticking on the pilot; which led to my joke about Continental pilots being better than Lycoming pilots. A dubious proposition indeed!
I also challenged any pilot to purposely create valve sticking by operating the engine in some way. So far none of the "its the pilot's fault crowd" can meet the challenge. So valve sticking appears not to be caused by the pilot.
We also noticed that when the valve ran hotter than normal (because of valve leakage) that there was more sticking. We then concluded that the reason Lycoming exhaust valves stick more than Continental was because the Lycoming valve stem is hotter.
This is a quote from an article I wrote in 2009
"If the valve sticks closed and doesn't open in 1/2 propeller revolution the rocker arm supports will blow-off leading to total loss of engine power."
[article link]
The reason the rocker boss supports blow is that when the exhaust valve doesn't open the gas is not released and creates very high pressures that hold the intake valve closed. When the intake rocker arm tries to open the valve it doesn't budge and something has to give. The rocker boss at the intake fractures. You see this on the Continental O-200 because the rocker boss supports on older style cylinders are thin and rather frail.
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....assuming normal stem-to-guide clearance.
Captain Avgas
Well Known Member
Thank you for your explanation. The Lycoming valve HEAD is cooler, but the valve STEM is hotter than for a Continental.
Intuitively I would have thought that the valve guide protrusion on the Lycoming design would have protected more of the Lycoming valve stem from hot exiting exhaust gasses, thus rendering the stem cooler.
Greg Arehart
Well Known Member
Update
It has now been over a month since the last post and I'm sure that at least a few folks are still interested in what is happening.
I pulled all four working cylinders and dropped them at Eagle Engines (Redding, CA) and they have been inspected there. Lots of carbon in the system, and their interpretation is that the carbon buildup was probably the root cause of a stuck valve, which ultimately resulted in the boss failure. For those of you interested in the wobble test, I forgot to ask what they found on this. In addition to the carbon, all four (including the new one) pistons are scuffed on the sides, and appear to have metal (probably aluminum) embedded in the pistons. Because of weather and other complications, I have not yet talked with Lou at Eagle in person, so I'm not seeing all that he is seeing.
More data: Last weekend, I pulled apart all of my old oil filters (I knew I was keeping these for some reason!) to look for obvious metal. There were a few more flecks of aluminum in the most recent filter (removed just after coming back from Jean), but nothing that seemed extraordinary. Oil analysis came back normal. Absolutely zero metal in the screen. I also filtered that last 6 quarts of oil through a cloth, and zero metal there either.
So, I'm pretty confused about the entire thing. I still don't know why the engine is so carboned up, since I religiously run LOP except sometimes on the ground (only a few minutes at a time) and during takeoff (I typically run rich for cooling, but again, only for a few minutes). Perhaps the carbon accumulated during my last descent into RTS where I was basically power off from 12000 down to 5000, then minimal power for taxi? How much carbon can accumulate during those ~10-12 minutes, I don't know. I haven't looked at enough engines to really know what to expect.
I have talked to a metallurgist friend here at the university, and he is going to have a look at the parts and give me his opinion on the failure mode, which I will eventually post here.
After much thinking and talking with a lot of people, I have come to the conclusion that because of the metal embedded in the pistons, it seems wise to pull the engine apart and figure out if anything else has been affected. I don't think I would feel totally comfortable flying over rough terrain without doing this. I'm hoping that my metallurgist buddy will be able to shed some light on the failure mode, which will guide my decision as to whether the other Superior cylinders are suspect and might need replacement.
Bottom line is that the teardown and inspection is going to be in the $8500 range (ouch!). With the money I've already spent on this "event," that works out to about $30/flying hour for the 337 hours on the engine so far. Nobody said this was a cheap hobby, but I could have used a couple hundred more hours before having this happen. I just hope I'm the only one.....
Cheers,
greg
It has now been over a month since the last post and I'm sure that at least a few folks are still interested in what is happening.
I pulled all four working cylinders and dropped them at Eagle Engines (Redding, CA) and they have been inspected there. Lots of carbon in the system, and their interpretation is that the carbon buildup was probably the root cause of a stuck valve, which ultimately resulted in the boss failure. For those of you interested in the wobble test, I forgot to ask what they found on this. In addition to the carbon, all four (including the new one) pistons are scuffed on the sides, and appear to have metal (probably aluminum) embedded in the pistons. Because of weather and other complications, I have not yet talked with Lou at Eagle in person, so I'm not seeing all that he is seeing.
More data: Last weekend, I pulled apart all of my old oil filters (I knew I was keeping these for some reason!) to look for obvious metal. There were a few more flecks of aluminum in the most recent filter (removed just after coming back from Jean), but nothing that seemed extraordinary. Oil analysis came back normal. Absolutely zero metal in the screen. I also filtered that last 6 quarts of oil through a cloth, and zero metal there either.
So, I'm pretty confused about the entire thing. I still don't know why the engine is so carboned up, since I religiously run LOP except sometimes on the ground (only a few minutes at a time) and during takeoff (I typically run rich for cooling, but again, only for a few minutes). Perhaps the carbon accumulated during my last descent into RTS where I was basically power off from 12000 down to 5000, then minimal power for taxi? How much carbon can accumulate during those ~10-12 minutes, I don't know. I haven't looked at enough engines to really know what to expect.
I have talked to a metallurgist friend here at the university, and he is going to have a look at the parts and give me his opinion on the failure mode, which I will eventually post here.
After much thinking and talking with a lot of people, I have come to the conclusion that because of the metal embedded in the pistons, it seems wise to pull the engine apart and figure out if anything else has been affected. I don't think I would feel totally comfortable flying over rough terrain without doing this. I'm hoping that my metallurgist buddy will be able to shed some light on the failure mode, which will guide my decision as to whether the other Superior cylinders are suspect and might need replacement.
Bottom line is that the teardown and inspection is going to be in the $8500 range (ouch!). With the money I've already spent on this "event," that works out to about $30/flying hour for the 337 hours on the engine so far. Nobody said this was a cheap hobby, but I could have used a couple hundred more hours before having this happen. I just hope I'm the only one.....
Cheers,
greg
Greg Arehart
Well Known Member
Dan,
In the skirts. The hypothesis is that the metal (aluminum, not steel) got into the oil (presumably rocker boss bits that went through the oil drain line) and was splashed onto the cylinder walls etc. by the movement of the crankshaft. I have the spray nozzles in the engine, but obviously any metal going through the pressurized oil system would have been caught by the filter.
greg
In the skirts. The hypothesis is that the metal (aluminum, not steel) got into the oil (presumably rocker boss bits that went through the oil drain line) and was splashed onto the cylinder walls etc. by the movement of the crankshaft. I have the spray nozzles in the engine, but obviously any metal going through the pressurized oil system would have been caught by the filter.
greg
Only times I have seen metal in the skirts is from cam lobe and tappet face failure. Has anyone glanced at the cam?
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
Greg Arehart
Well Known Member
Mahlon,
We looked at the cam after pulling the cylinders and nothing obvious, but it will get a close scrutiny when we open things up.
greg
We looked at the cam after pulling the cylinders and nothing obvious, but it will get a close scrutiny when we open things up.
greg
detlef lili
Well Known Member
Thanks Greg, for the update.
I still watch this thread since I have the same engine, with the same time and also run mostly on car gas. You fly mostly over rough terrain and we a lot over water. (We also visited Reno last summer, we were invited by Chuck Harder)
And we don?t like any surprise flying over the ocean. So we are very interested in the results. Please keep us informed.
Detlef
I still watch this thread since I have the same engine, with the same time and also run mostly on car gas. You fly mostly over rough terrain and we a lot over water. (We also visited Reno last summer, we were invited by Chuck Harder)
And we don?t like any surprise flying over the ocean. So we are very interested in the results. Please keep us informed.
Detlef
Larry L Driver
I'm New Here
Another Superior Rocker Boss Failure
Hi, All.
I was just made aware of this posting by another member.
I too experienced a rocker boss failure on my Superior XP I0-360 yesterday while flying cross country over Missouri. My RV7 first flew in July 2005 and has 675 hours.
I was able to get to an airport 11 miles north under very reduced power. Removed the cowl and saw what Greg described and illustrates in his photos. Failure looks identical, including the much thinner side of the casting of the boss.
I had had an incident of roughness on the previous leg that went away after enrichening. I also thought it might be contaminants or water in the fuel. Like Greg, there was no indication of something catastrophic... just a rough engine. Doesn't appear that I lost much oil. Just some spray inside the cowl. Oil pressure remained normal. Haven't checked the oil level. Was en route to a business meeting and had to leave plane behind. Will definitely check the oil on return, though.
Larry
N977RV
Phoenix AZ
Hi, All.
I was just made aware of this posting by another member.
I too experienced a rocker boss failure on my Superior XP I0-360 yesterday while flying cross country over Missouri. My RV7 first flew in July 2005 and has 675 hours.
I was able to get to an airport 11 miles north under very reduced power. Removed the cowl and saw what Greg described and illustrates in his photos. Failure looks identical, including the much thinner side of the casting of the boss.
I had had an incident of roughness on the previous leg that went away after enrichening. I also thought it might be contaminants or water in the fuel. Like Greg, there was no indication of something catastrophic... just a rough engine. Doesn't appear that I lost much oil. Just some spray inside the cowl. Oil pressure remained normal. Haven't checked the oil level. Was en route to a business meeting and had to leave plane behind. Will definitely check the oil on return, though.
Larry
N977RV
Phoenix AZ
Larco
Well Known Member
I have seen pictures of both Larry's and of Greg's failure and they look identical. What would be interesting is if they are close in serial numbers. Could you both please post that info, I have a feeling that there are more failures ahead of us. Hopefully I'm way off base. Larry S
Larry L Driver
I'm New Here
Cylinder Serial Numbers
I will certainly post my serial number for comparison. It will be sometime after next Friday when I get back to the airport where I had to leave the plane for repair.
I will certainly post my serial number for comparison. It will be sometime after next Friday when I get back to the airport where I had to leave the plane for repair.
Larry L Driver
I'm New Here
Ken,
I've had numerous e-mail conversations with Superior. They're convinced it's a stuck valve.
I'm in a total quandary as to how to fly the airplane now. I always fly LOP below 70% power. Plugs has always been pretty clean. So carboned up valves doesn't seem likely.
Not a very comforting thought that you might have the same thing happen without any warning over less friendly terrain.
Hopefully, I'll learn more when we change the cylinder later next week. Although it sounds like nothing definitive ever developed in Greg's case.
Maybe we should have a "Superior Engine Owners Get-Together" at AirVenture.
I've had numerous e-mail conversations with Superior. They're convinced it's a stuck valve.
I'm in a total quandary as to how to fly the airplane now. I always fly LOP below 70% power. Plugs has always been pretty clean. So carboned up valves doesn't seem likely.
Not a very comforting thought that you might have the same thing happen without any warning over less friendly terrain.
Hopefully, I'll learn more when we change the cylinder later next week. Although it sounds like nothing definitive ever developed in Greg's case.
Maybe we should have a "Superior Engine Owners Get-Together" at AirVenture.
Larry L Driver
I'm New Here
Here are my cylinder serial numbers if anyone would like to compare:
#1 366WCO45613
#2 366WCO45604
#3 366WC045865
#4 366WC045866
#1 366WCO45613
#2 366WCO45604
#3 366WC045865
#4 366WC045866
Larry L Driver
I'm New Here
Ken
I wish I had been a better documentarian. I'm really not sure. I know at times different cylinders would reach EGT peak first, I think, usually #2 or #3. As for CHTs, #1 and #3 were the hottest best of my recall. But again, I'm not very confident in that.
I have an Advanced AF2500. Not sure if I have the ability to do a "data dump" and I may not be able to come up with the cable, but I may look into that before it's flown again.
I wish I had been a better documentarian. I'm really not sure. I know at times different cylinders would reach EGT peak first, I think, usually #2 or #3. As for CHTs, #1 and #3 were the hottest best of my recall. But again, I'm not very confident in that.
I have an Advanced AF2500. Not sure if I have the ability to do a "data dump" and I may not be able to come up with the cable, but I may look into that before it's flown again.
Greg Arehart
Well Known Member
I'm in the middle of central Yukon in a camp 20 miles from my airplane, but will try to post serial numbers when I return to Reno from this trip in a week or so. Interesting (and a bit scary) to see a similar failure. I have a metallurgical colleague who is supposedly looking at the parts this summer, but I've been gone for several weeks now. I will post something if/when he gives me information.
cheers,
greg
cheers,
greg
Were these carb'ed engines
I have a Superior IO-360 I built at the build school in November 2007. Based on this thread I checked my serial numbers and my numbers are 366WG0712470 tightly grouped in a range to 487. I am not sure what the "W" means, mine is Fuel Injected - maybe that is it. Just trying to figure out if mine are in the same range of suspect cylinders and whether its worth pulling the jugs to have the valve guides check. Calender build time they are for sure.
Be interested to see if we have anymore failures and what their SN's are.
I have a Superior IO-360 I built at the build school in November 2007. Based on this thread I checked my serial numbers and my numbers are 366WG0712470 tightly grouped in a range to 487. I am not sure what the "W" means, mine is Fuel Injected - maybe that is it. Just trying to figure out if mine are in the same range of suspect cylinders and whether its worth pulling the jugs to have the valve guides check. Calender build time they are for sure.
Be interested to see if we have anymore failures and what their SN's are.
Larry L Driver
I'm New Here
This past Friday I was able to pick my plane up in MO after having a new #3 cylinder installed. The mechanic also reamed the exhaust valve guides of the other cylinders on the suggestion that this was possibly caused by a stuck valve. He said they were pretty clean and the valves moved freely but went ahead with the reaming.
Upon returning, we inspected the failed #3 cylinder. After removing the spring from the exhaust valve, it was apparent it was stuck big time. We actually had to tap it out with rod and a hammer. There was lots of carboning/coking, whatever you want to call it, in the valve guide.
I still don't have a clue why this was a problem on this cylinder, but I would pass along some observations:
First, I had several instances of roughness - probably less than 2 seconds in duration - before this occurred.
Second, I had had a couple instances of what might considered "morning sickness."
Third, and I have no idea if there's a connection, but almost from the beginning with this engine my oil would start to turn dark in a very short time (2 -3 hours) after every change. I've now flown about 8 hours since the cylinder change and the oil looks just absolutely clean as when it came out of the bottle. So I have to wonder if this cylinder hasn't been "sick" for a very long time.
Larry
Upon returning, we inspected the failed #3 cylinder. After removing the spring from the exhaust valve, it was apparent it was stuck big time. We actually had to tap it out with rod and a hammer. There was lots of carboning/coking, whatever you want to call it, in the valve guide.
I still don't have a clue why this was a problem on this cylinder, but I would pass along some observations:
First, I had several instances of roughness - probably less than 2 seconds in duration - before this occurred.
Second, I had had a couple instances of what might considered "morning sickness."
Third, and I have no idea if there's a connection, but almost from the beginning with this engine my oil would start to turn dark in a very short time (2 -3 hours) after every change. I've now flown about 8 hours since the cylinder change and the oil looks just absolutely clean as when it came out of the bottle. So I have to wonder if this cylinder hasn't been "sick" for a very long time.
Larry
Greg Arehart
Well Known Member
Roger,
I'm still not home (stuck in Smithers BC with claggy weather this morning) but I built my engine (IO360) in Dec 2007, so probably similar numbers. I never noticed any morning sickness but the engine was running roughly immediately prior to the failure. When the engine was rebuilt, Lou at Eagle Engines said that there was a lot of carbon in the engine even though I run LOP consistently. He attributed it to the injector body not being set quite right.
greg
I'm still not home (stuck in Smithers BC with claggy weather this morning) but I built my engine (IO360) in Dec 2007, so probably similar numbers. I never noticed any morning sickness but the engine was running roughly immediately prior to the failure. When the engine was rebuilt, Lou at Eagle Engines said that there was a lot of carbon in the engine even though I run LOP consistently. He attributed it to the injector body not being set quite right.
greg
Larry L Driver
I'm New Here
Walt,
I would use about 1 quart of oil in 15 -16 hours. I didn't consider that high oil consumption. Nor did the #3 plugs ever show any signs.
Larry
I would use about 1 quart of oil in 15 -16 hours. I didn't consider that high oil consumption. Nor did the #3 plugs ever show any signs.
Larry
