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Bent Push Rod

Omega232Devils

Omega232Devils

Well Known Member
I pulled the cowling today after an hour flight to do an oil change and while waiting on the oil to drain, I inspected the FWF. This is what I found:

IMG_20120225_192256.jpg


I have a picture taken 5 days ago, when I had the top cowling off working on my baffling and the pushrod tube was straight.
IMG_20120216_151432.jpg

So this happened in the past 5 days were I have put 5 flights and 5.5 hours on the engine. I haven't had any engine issues that would make me suspect this and no telling how long I would have flown on it without pulling the cowling for an oil change.

What could have caused this? What can I expect? Where should I start? Is this an easy fix? Any help is greatly appreciated.

Dan

Lycoming 0-360-A1A
One Slick & One ElectroAir EI (old Jeff Rose)
 
Changing the tube is easy

I bent the aft tube on cylinder #4 stupidly useing a crow's foot on the spark plug. It was quick and easy to change by the A&P I called to do it. It seems to me finding the cause is as important to find as getting it fixed and I know that is what you are looking for here. The pushrod inside is not very large compared to the inside diameter of the tube. If the associated valve stuck the pushrod may be bent. Good luck.

Bob Axsom
 
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A stuck valve is definately the most likely cause of the bent pushrod/pushrod tube. I'd be surprised if you didn't notice some rough running (morning sickness) symptoms.
 
Baffle seal around flywheel

FYI - your baffle seal at your flywheel is reversed.
Alan Jackson
 
Current time is 571.7 on engine since teardown for a prop strike that happened on first engine start in 1999.

Walt, only hickup i noticed was right after takeoff, it was momentary, enough that i noticed it, but not long enough for me to think I wasn't just hearing things! I did a full run up prior to takeoff and the were no issues. That was on first of three flights yesterday. No other issues on next two flights.

Will the cylinder have to come off to fix this or can the tube/rod be replaced and borscobe to look at valves?

I have not been using MMO, should I?

Dan
 
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Good catch

Alan,
Good catch. The picture you are seeing is the one I took 5 days ago before I replaced the baffling. I took it in case i messed something up I would have a reference. The baffling is now correct and to my surprise my CHTs lowered 10deg. (I was only expecting 2-3 deg drop):)

Dan
 
Dan,
I agree with Walt. I'd say that it's bit late for you to read Lycoming Service Letter L197A or Service Instruction SI 1425A, which detail how to avoid the predicament you find yourself in. Looks like you need to check out your valves and valve guides for excessive deposit buildup. You will need to replace the affected push-rod and push-rod tube. Hopefully, you will be able to correct the problem by reaming the valve guides
I would suggest you read SB 388C, SB404, SSP 475 & SI 1193A. You can download SB 388C below.

http://www.lycoming.textron.com/support/publications/service-bulletins/index.html

SI 1425A can be downloaded at

http://www.lycoming.textron.com/support/publications/service-instructions/index.html

I can supply the others, if you need them.

Charlie
 
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Charlie,
It is not too late for my other 3 cyllinders. I will read the documents.

Thanks very much,

Dan
 
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best money spent will be to let a professional help you moving forward. Hire a reputable Aircraft Engine Tech and let him decide for you after a throughout inspection...

Way Too many things could have have gone wrong before and after the incident..lets start at the lowest side...your Cam Lobe? how about the lifter? the next two thing are the only one you are sure in need to change which are the tube and rod....How about your rocker arm, Valve, valve guide, seat....are you sure your valve did not strike your piston? how about the Cylinder itself! ....way too many variables involved!

I now it sucks right now...but let a Pro help you
 
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Useful Service Instruction

mv031161 said:
snipped
Way Too many things could have have gone wrong before and after the incident..lets start at the lowest side...your Cam Lobe? how about the lifter? the next two thing are the only one you are sure in need to change which are the tube and rod....How about your rocker arm, Valve, valve guide, seat....are you sure your valve did not strike your piston? how about the Cylinder itself! ....way too many variables involved!
snipped
Click to expand...

Dan,
SI 1193A that I mentioned in my first post, will help you check other possible issues that Mitch refers to above.
Charlie
 
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happened to me

Long time ago had the same problem on an O-320. ran surprisingly smooth but only on 3 cylinders. did a static run up FT and would not make the minimum staitc RPM. Cowl came off (172) and engineer found a bad pushrod/valve. Surprising how smooth it ran.
 
Thanks guys!

I am glad I am not crazy, but not happy about the teardown and inspection. Just another chapter in my owner learning experience.

I am meeting with an engine mech today. Two things I do not mess with are:
1) That which makes the plane go
2) That which keeps it in the air!

All the knowledge and advice here is AWESOME!

Dan
 
mv031161 said:
are you sure your valve did not strike your piston? how about the Cylinder itself! ....way too many variables involved!
Click to expand...

Its completely impossible for a valve to strike a piston on a Lycoming. Even with the cam 180 degrees out of time there's still over 1/2" of clearance.
 
rocketbob said:
Its completely impossible for a valve to strike a piston on a Lycoming. Even with the cam 180 degrees out of time there's still over 1/2" of clearance.
Click to expand...

you are right, but others issues involved that can make it hit. here is one from Mike Bush

http://www.avweb.com/news/maint/182849-1.html
Lie #1:
Lycoming engines are better than Continental engines.
(Or vice-versa.) I bought my first airplane 30 years ago. It was a Cessna 182 powered by a Continental O-470-R engine. Since then I've owned a succession of airplanes, and each one-quite coincidentally-was powered by a big-bore Continental. My engines have always made TBO and been relatively trouble-free. So it's not surprising that I'm something of a fan when it comes to TCM engines. It's equally unsurprising that at least half the pilots and aircraft owners I meet are Lycoming bigots. They brashly state "I'd never own a Continental-powered airplane!" If you ask why, they'll tell you a series of anecdotal episodes about how their Lycoming-powered Turbo Saratoga made it to 1,000 hours past TBO, while their best friend wound up having to tear down the TCM factory reman in his Mooney 231 or Beech B36TC after just 475 hours.
Let's set the record straight. Lycoming and TCM engines are very similar designs using very similar technology and metallurgy. Both are horizontally-opposed air-cooled designs with bolt-together aluminum case halves and bolt-on cylinders with sandcast aluminum heads screwed onto nitrided steel barrels. Both use fixed-timed dual magneto ignition systems, and valve trains with overhead rocker arms, shrouded hollow pushrods, and hydraulic valve lifters. Both use similar compression ratios, similar RPM red-lines, and similar power-to-displacement ratios. And both have comparable records of reliability and longevity.
Certain problems tend to occur more frequently in one brand or the other. Continentals have a lot more crankcase cracks, head-to-barrel separations, and premature valve guide wear problems than Lycomings. On the other hand, Lycomings suffer stuck and broken valves and spalled cams and lifters much more often Continentals.
Some TCM and Lycoming models have better track records than other TCM and Lycoming models. For example, the TCM TSIO-360 series (used in Mooneys, Skymasters, and various other aircraft) tend to be more troublesome and maintenance-intensive than other Continentals. Likewise, the Lycoming O-320-H2AD engine has had a dismal history of cam and lifter problems when flown irregularly and operated in cold climates.
But while certain specific TCM and Lycoming models are problem-prone, it is simply wrong to make a general assertion that engines of either manufacturer are more reliable than those of the other. It's just not so.
 
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Omega232Devils said:
I am glad I am not crazy, but not happy about the teardown and inspection. Just another chapter in my owner learning experience.

I am meeting with an engine mech today. Two things I do not mess with are:
1) That which makes the plane go
2) That which keeps it in the air!

All the knowledge and advice here is AWESOME!

Dan
Click to expand...

He can accomplish lots just by removing that one cylinder. Good luck! let us know what you find!
 
Photos...

I'm struck by the fact you have such recent photos for comparison. Hmmm, I'm going to start taking photos of the enginge every time I open the hood. What a fortuitous benefit for you.

I wish you the best with this.
 
Update!

First off, thanks very much for all the help and information!

I went to the hangar today and met with a very well respected mechanic who teaches A&P classes at the local college here in San Diego. He thought it best to pull the cyllinder and get the valves checked. So I pulled the cover off and this is the first thing I saw:

IMG_20120226_114142.jpg


So the sticky valve was quick enough to bend the push rod and knock the rotator cap off. There is a small nick in the rotator cap and in the top of the valve spring retainer.

IMG_20120226_162635.jpg


The push rod was definitely bent:

IMG_20120226_133502.jpg


No damage to the piston or cam. I am taking the cylinder to a local shop tomorrow to have it repaired.

Below are a couple more photos:

IMG_20120226_162558.jpg

IMG_20120226_162708.jpg


One thing I looked back on, was the previous cowling removal (5 days before this) was to change the baffling behind spinner to face correct direction. After any modification I always fly a standard profile in which I collect data in respect to my CHTs. (I have been trying to lower CHTs since I bought the plane.) After the baffling mod, I did a CHT run (1st of 5 flights I talked about in this thread) and before takeoff, noted the EGT of #2 cylinder was 760 degrees, 300deg below other 3 cylinders. I didn't think anything of it at the time as it was post run up. In flight all EGTs were normal across the board, so I chalked it up to just a sensor glitch. Some guys on here have noted that low EGTs at low RPM are a sign of a potential sticky valve.

IMG_20120226_162723.jpg


I will update more tomorrow when I talk to the guys at the engine shop when I drop the cylinder off.

I hope this will help anyone else in the same situation.

Dan
 
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Omega232Devils said:
First off, thanks very much for all the help and information!

I went to the hangar today and met with a very well respected mechanic who teaches A&P classes at the local college here in San Diego. He thought it best to pull the cylinder and get the valves checked. So I pulled the cover off and this is the first thing I saw:

IMG_20120226_114142.jpg


So the sticky valve was quick enough to bend the push rod and knock the rotator cap off. There is a small nick in the rotator cap and in the top of the valve spring.

snipped

Dan
Click to expand...

Dan,
The nick is in the top valve spring retainer, not the valve spring itself. I would strongly suggest that your mechanic check the valves on the other 3 cylinders. If heavy deposit build up is found, remove the cylinders and clean up as needed. At the very minimum, follow Lycoming's SB 388C & SI 1425A [aka The Rope Trick] which I referenced in an earlier post. If one valve is sticking, the others are probably not far behind it.
Charlie
 
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Actually, the valve probably stuck open, the cap fell part way out, and was smashed by the rocker on the next valve opening event. The clearance taken up by the crooked valve cap caused the valve spring to be compressed until the coils bound up into a solid stack. Then the pushrod was bent as the camshaft continues to rise against solid resistance.
Valves almost always stick in the open condition. The cam opens the valve because it is strong enough. the tight valve guide (carbon clogged etc) holds the valve open, the spring is not strong enough to pull it closed in time to follow the cam as it falls away. After the pushrod bent, the cap fell out the rest of the way, where you found it in the bottom.
You might want to replace the valve spring, or check it for strength and defects.
The rocker arm face probably has a scar from pushing on the edge of the hardened cap. That might need to be refaced or the rocker replaced.
Every part from the cam lobe to the valve was overstressed by the mechanical lockup that bent the pushrod.
Lycoming probably has a document on this type of failure.
It's fairly important to keep the big fan turning. :rolleyes:
 
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SHIPCHIEF said:
Actually, the valve probably stuck open, the cap fell part way out, and was smashed by the rocker on the next valve opening event. The clearance taken up by the crooked valve cap caused the valve spring to be compressed until the coils bound up into a solid stack. Then the pushrod was bent as the camshaft continues to rise against solid resistance.
Valves almost always stick in the open condition. The cam opens the valve because it is strong enough. the tight valve guide (carbon clogged etc) holds the valve open, the spring is not strong enough to pull it closed in time to follow the cam as it falls away. After the pushrod bent, the cap fell out the rest of the way, where you found it in the bottom.
Click to expand...

What he said.

Also, take a good look at the base of the boss for the rocker arm shaft, there have been a couple reports of these cracking.

Here is the thread Greg Arehart had on this last year.

http://www.vansairforce.com/community/showthread.php?t=66233
 
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SHIPCHIEF said:
snipped
Every part from the cam lobe to the valve was overstressed by the mechanical lockup that bent the pushrod.
Lycoming probably has a document on this type of failure.
It's fairly important to keep the big fan turning. :rolleyes:
Click to expand...

Scott,
That would be SI 1193A, which I referenced earlier. It explains what needs to be checked, after a valve failure. SI 1425A relates to repair of sticky valves in particular.
Charlie
PS I can supply this document and the others I mentioned earlier, to anyone who wants them. Contact me via email [see my VAF profile] if interested.
 
Dan,
Looks like you have a handle on this issue now. Please keep us posted on your progress as many are watching this thread to learn. It is good to share results with the RV community.
 
In repair shop now!

I dropped the cylinder off at the repair shop this morning and after a quick look, the mechanic said pretty much what "Shipchief" said above.

I am waiting to hear back from him, but said at a minimum he is going to ream the exhaust valve and test the parts (rocker, springs, etc). The engine shop is highly recommended, so I am sure they will do right by me. I will continue to update and post some after repair pictures as well.

The inside of the case was fully inspected and everything appeared in great shape. I am knocking on wood, but it seems that I caught it early enough (and the sticky valve was only momentary) to not cause more damage. One thing I am learning, and hope others take away from this, is although the push rod shroud was only slightly bent (enough to notice, but not as gross as ones you can Google!), but the damage is on the inside. Don't take ANYTHING lightly!

Dan
 
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Omega232Devils said:
Clipped........
I am waiting to hear back from him, but said at a minimum he is going to ream the exhaust valve and test the parts (rocker, springs, etc). The engine shop is highly recommended, so I am sure they will do right by me. I will continue to update and post some after repair pictures as well.
Dan
Click to expand...
If I recall correctly, a major suspect for sticking valves is excess clearance between the guide and valve leading to deposits in the guide. Reaming the guide might not completely solve your problem. If the valve is within service limits, might it not be prudent to replace the guide and ream to the correct limits?
 
Same Same

Mark,
Keep in mind, I am not an engine expert and most of the time I am repeating what people smarter than me are saying (Atleast an attempt to remember everything that was said as I am learning). When I get the update from the engine shop on exactly what is going to be done I will post this so as not to confuse anyone. I have no doubt that the engine shop will do what is required. I am not cutting corners when it comes to the engine, so if there is a doubt, there is no doubt. It will be fixed properly.

Dan
 
Of course, Dan! Neither am I by a long stretch.
Good luck with getting it sorted, and hope you are flying again soon.
 
So at what point is reaming guides (or does one need to do the wobble test?) required?

Does this depend on,

1) If you run 100LL
2) never run LOP


I.e if you always run LOP and hardly ever run 100LL (like me) when should one perform this test?

Why not do the rope trick and just run a reamer through the guides every 500 hours?

Am I missing something?

Frank
 
Cylinder Repaired

UPDATE:
I picked up my cylinder today: There was definite evidence of a sticky valve as the exhaust valve had quite a bit of build up on it. So they replaced the valve, reamed the guides and base.

Upon cleaning off the piston, this is what they found:
IMG_20120301_125140.jpg

IMG_20120301_125134.jpg


It appears something made its way into the intake system and spent a few rounds inside. I am not sure if two issues (bent push rod and damage piston head) are concurrent. (I suspect they are!) They replaced the piston head, new rings and honed the cylinder! I should be good to go on the new cylinder!

Now the question is:
1) What could have caused the damage to the piston head? (Engine mech thinks it was a screw based upon certain indent marks.)
2) Where did the piece come from?
3) What should I inspect in order to find the culprit?

I plan to pull the intake and filter, carb heat assembly and bore scope each cylinder. Where else should I look?

I hope someone else is getting something out of this thread. It has been very educational for me. The one thing that is really bugging me is if I can't find a missing screw/fastener or anything that could have done the damage. This would mean that it came from an outside source and I am very particular, (read that: extremely anal) about tool and hardware accountability. 12 years in Military aviation has groomed me to be such. I do not replace screws/fasteners etc, just because I can't find one. I always do a one for one swap! I inventory my tools and ensure they are placed in proper spot each and everyday. I do not leave the hangar overnight with tools and hardware adrift. So I am hoping to find the culprit to set my mind at ease.

Again, all help and ideas are greatly appreciated.

Looking forward to flying again soon.

Dan
 
Omega232Devils said:
Now the question is:
1) What could have caused the damage to the piston head? (Engine mech thinks it was a screw based upon certain indent marks.)
2) Where did the piece come from?
3) What should I inspect in order to find the culprit?

I plan to pull the intake and filter, carb heat assembly and bore scope each cylinder. Where else should I look?




Again, all help and ideas are greatly appreciated.

Looking forward to flying again soon.

Dan
Click to expand...


Could it be part of a spark plug? A chip of helicoil? Or something may get inside accidentally when the plug was out? (I understand military anality :D it may bite you too) I am suggesting non-intake way.
 
Pop rivets? Safety wire?

Missing any pop rivets or chunks of safety wire used to put the intake or airbox together?

Dan
 
Good points!

All good points!

Both plugs are in tact, but good idea about debris getting in when removed. NOTE: get more hole plugs to prevent this, put some in travel tool bag.

Safety wire and rivets good. Only work I have done recently is replace baffle seal on mouth of air intake. 8 pop rivets removed. (8rivet heads, 8 steel inserts and 8 bodies accounted for) I also stuffed rag in intake prior to removal and ran a magnet and vacuum through it when complete. (Understanding the anal detail yet!?) Haha. :D

I spoke to my A&P and he said the piston damage is not concurrent with bent rod.
The damage had too much age on it. We are still going to bore scope all cylinders and case to rule out everything.

Great ideas. Thanks guys!

EDIT: Just read last post again and when I was changing air intake baffle material, I noticed the hinge for my carb heat flap had broken a little. I even made a note to fix at next annual! If this broke off a piece could have done it. I will inspect it very closely next hangar day!
 
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So, are you thinking that somehow this piece of 'carb heat flap hinge' got passed the air filter? Unlikely if your filter is intact.

The other post was referring to the alternate air door as opposed to the carb heat door.

Good Luck with your follow up.....your findings will certainly help others....me included, thank you.

Omega232Devils said:
All good points!
Just read last post again and when I was changing air intake baffle material, I noticed the hinge for my carb heat flap had broken a little. I even made a note to fix at next annual! If this broke off a piece could have done it. I will inspect it very closely next hangar day!
Click to expand...
 
Omega232Devils said:
UPDATE:
snipped
IMG_20120301_125134.jpg


It appears something made its way into the intake system and spent a few rounds inside. I am not sure if two issues (bent push rod and damage piston head) are concurrent. (I suspect they are!) They replaced the piston head, new rings and honed the cylinder! I should be good to go on the new cylinder!

Now the question is:
1) What could have caused the damage to the piston head? (Engine mech thinks it was a screw based upon certain indent marks.)
2) Where did the piece come from?
3) What should I inspect in order to find the culprit?

I plan to pull the intake and filter, carb heat assembly and bore scope each cylinder. Where else should I look?

I hope someone else is getting something out of this thread. It has been very educational for me. The one thing that is really bugging me is if I can't find a missing screw/fastener or anything that could have done the damage. This would mean that it came from an outside source and I am very particular, (read that: extremely anal) about tool and hardware accountability. 12 years in Military aviation has groomed me to be such. I do not replace screws/fasteners etc, just because I can't find one. I always do a one for one swap! I inventory my tools and ensure they are placed in proper spot each and everyday. I do not leave the hangar overnight with tools and hardware adrift. So I am hoping to find the culprit to set my mind at ease.

Again, all help and ideas are greatly appreciated.

Looking forward to flying again soon.

Dan
Click to expand...

Dan,
At this point, it is immaterial what caused the indentations on your piston. What happens in these situations is one of two scenarios.

#1 Foreign object bounces back and forth between piston and head till it causes catastrophic failure [auto dis-assembly mode] Generally happens with a larger object.

#2 Foreign object bounces back and forth between piston and head until it can manage to exit via the exhaust valve/port. Usually happens with smaller item or item which gets beaten smaller by piston and combustion chamber.

It is quite possible that the object got caught [temporarily] between the exhaust valve and it's seat, on it's way out. This could have caused the valve's rotator cap [which you found laying in the rocker box] to fall out. It is also possible that the foreign object invasion happened at some time in the past, and did not get caught between the valve and it's seat. The deposit build up reported by your mechanic makes either "now or earlier" scenario, equally probable. Considering that your mechanic did not notice the indentations until "after" cleaning the carbon off the piston crown, I'd lean towards the indentation event occurring prior to the stuck valve. Recent occurrence would most likely have created "chips" in the carbon layer on the piston crown. I think your mechanic would have spotted that "right off".
The size of the indentations on your piston show that the object was quite small. My concern is: What did your mechanic do to smooth out the matching indentations on the combustion chamber surface? Any high spots not smoothed down can create a hot spot. This could lead to detonation in the future, when the CHT is high in that cylinder. You didn't think I was actually going to let you get a good night's sleep tonight, did you? :eek:
Looking for that object now, is simply an exercise in wasting time. It's gone.
Charlie
 
chaskuss said:
The size of the indentations on your piston show that the object was quite small. My concern is: What did your mechanic do to smooth out the matching indentations on the combustion chamber surface? Any high spots not smoothed down can create a hot spot. This could lead to detonation in the future, when the CHT is high in that cylinder. You didn't think I was actually going to let you get a good night's sleep tonight, did you? :eek:
Looking for that object now, is simply an exercise in wasting time. It's gone.
Charlie
Click to expand...

This is quite correct...... But raises another question.

One thing that jumps out at me, is that the distribution of the marks is pretty even all over the piston.

A "quite small" object should not make any marks toward the center of the piston, there is too much clearance in the combustion chamber area. The indention's should be limited to the squish band area, and concentrated at the lower side of the piston.

Could these marks have been made by someone chipping off a layer of carbon from the piston prior to its being installed in the engine??

Are there equivalent markings in the combustion chamber?
 
My question is about the level of deposits on the piston - is this normal?

__________________
Click to expand...

Yup, craters of the moon. Sometimes the lead will build up 1/8". Think what that does to compression ratio. Lycs I've torn down burning only car gas usually have just a brown film you can read the part number through.
More food for thought. I've seen foreign objects bounce around from one cylinder into the next. Sometimes an object will go through every cylinder, so I personally wouldn't be happy until I checked the rest of the pistons.
 
Wobble test

I didn't get an answer to my question..

So if you don't have the wobble test equipment, is it that much more work to just remove each valve every 500 hours and run a reamer through the guides?

If you (hardly) ever run 100LL how often should one do the WT/Reamer?

Thanks

Frank
 
Valve troubleshooting

I think the wobble test to make sure the valve guide isn't worn - if it is, what happens is the valve is at risk of "chunking" back into place and the stress will eventually fail the valve (read, you're looking for a place to land). I don't think a wobble test is to detect a potentially sticking valve.

Completely separate - the valve guide can build up some deposits that will cause the valve to stick - this can do valve train damage.

YMMV.

Dan
 
Frank,
Dan is correct. Worn guides can cause the valve face to seat slightly off center. Over time, it will have the same effect as constantly bending a coat hanger. The steel fatigues and the valve head will come off. Have you ever seen a valve head buried, edge-wise in a piston? I have. It's another variation on "auto dis-assembly mode".
Regarding the SB 388C checking tool. That's a good item for a group purchase. Perhaps you can persuade your local EAA Chapter or RV builders group to buy one, for everyone to share. Lots of EAA Chapters have a tool lending library for expensive tools.
Another option is Lycoming's Tool Rental program, detailed in Service Letter L234B. SSP 384 details all the special tools that Lycoming has available.
I can provide SSP 384. SL L234B can be downloaded from

http://www.lycoming.textron.com/support/publications/service-letters/index.html

Charlie
 
Who is sleeping these days?

Haha Charlie. I haven't slept well in a few nights.

I agree the more I think about it the indentation damage was probably prior to sticky valve. Thanks for all the ideas and i will rest easy knowing i probably won't find the culprit. I am still going to search and maybe find a spot where something is missing!

Mike good point, the engine was completely tore down and rebuilt in 1999 after a prop strike on first engine start. (Builder was excited and didn't clear propeller area before starting)

I am hoping the bore scope will tell us more, good or bad!

More next week when I get back in town and get out to hangar!

Dan
 
SB 338

DanBaier said:
I think the wobble test to make sure the valve guide isn't worn - if it is, what happens is the valve is at risk of "chunking" back into place and the stress will eventually fail the valve (read, you're looking for a place to land). I don't think a wobble test is to detect a potentially sticking valve.

Completely separate - the valve guide can build up some deposits that will cause the valve to stick - this can do valve train damage.
Click to expand...

No, the wobble test checks for both a tight and a loose valve.

My Tiger heads failed in the loose (worn) direction, which is a valve breakage scenario as mentioned above - and it usually happens on take-off...:eek:

The sticky valve problem will be detected as a "wobble number" that is too low (tight in the guide).
 
Update!

Ok guys, sorry it has taken me so long to post an update. Today was the first day my A&P was available to help with putting the jug back on.

This week I did an inspection trying to find the culprit, or evidence of where culprit came from. I posted earlier that I thought maybe part of my carb heat hinge had broken off, but that was not the case. Not to draw this thread off topic, but here is some info on my carb heat hinge. The aluminum hinge was worn completely through on one side and about 20% on the other hinge.
IMG_20120306_143357.jpg


The previous owner used these thin aluminum strips epoxied in place to try and re-enforce the hinge. This was a bandaid fix and a pretty poor fix at that.
IMG_20120306_143503-1.jpg

IMG_20120306_143537.jpg


The carb heat hinge failing is well documented on VAF, so after some good reading and talking with a few members (Thanks Scott and Gary) I replaced the hinge with the 'Zilik' hinge using baffle material as the hinge. I am very happy with the result and think it will work for some time!
IMG_20120306_164906.jpg



Ok, on to the new jug. Nothing too exciting here. We installed the new jug with very little issues. We did bore scope the other cylinders and found no issues with number 1&3. Cylinder 4 showed some signs of heat damage and my A&P suspects it will be the first to lose compression and will need to be corrected. Not sure how long that will take, but I will keep an eye on it.

We started the engine up and let it run for 30 seconds with good oil pressure, then checked for leaks. All looked good. Did that once more, then a longer 2 minute run with a Magneto check and no problems. Put the cowlings on and took her for a 30 minute race track flight overhead the field. Running 25^2 to keep the pressure high for the rings to seat. I was surprised at the temperatures I was seeing. All the reading and research, I was expecting to see the new cylinder at least 30-40 degrees hotter than the other cylinders. This was not the case, the hottest #2 got was 352 degrees. (Climbed to 2600' AGL) After 7 minutes the CHT dropped to 344 and after 22 minutes dropped to 332 and stayed there for the rest of the flight. I know running 16 gph through there will keep it cool (my wallet was getting hot though!), but the new cylinder was inline with the other cylinders. (i.e. Two front cylinders were within a few degrees and back two cylinders were within a few degrees of one another)

After landing, pulled the cowlings to look for a leak and found a small evidence of a leak! :eek: Turns out the new flex hose I installed in the oil return lines while the cylinder was off, just needed to be tightened a bit! :cool: EASY FIX!

Tomorrow it is time to burn some more cash and seat those rings! Thanks for all the help again VAF!

Dan
 
I just had to pull a cylinder for a leaking exhaust valve. On the test flight we found the same thing that you did. The CHT on that cylinder was basically normally from level off at 1000 feet. It was a nickel carbide cylinder honed by Penn Yan. They are noted to break in very fast.

George
 
Ream

As Frank asked, and Charlie has implied with the Lycoming SI's. You may find it worth the time to take preventative reaming measures on the other three valves. While a bit cumbersome labor-wise, I think you'll find clean valve-guides to be a much nicer alternative to a permanently stuck valve in flight, especially one any less docile then the on you experienced. We are in a hot/dry summer climate and some local mechanics feel it's worth doing at the interval suggested in the SI...
 
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