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Need to replace Cylinder 2 and muffler


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Here is a picture of the valves.  Taken from above the cylinder once it was removed. 

I'll have to search more of your lingo, as you suggest.  But the "morning sickness" behavior was something I'd read about and since this engine often had relatively rough starts over the winter that calmed out at runup, I just got used to it.  Though, looking through the JPI graphs, it was getting worse and worse and I should have put 2 and 2 together. 

Do you have JPI fuel flow, it’s helpful to add that to the graph?

FWIW, many run LOP and go well past TBO...myself included.

 

Tom

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6 hours ago, Shadrach said:

Rope trick is a method of removing a valve from its guide, reaming the guide and reinstalling the valve with the cylinder still mounted to the engine. It is outlined in Lycoming Service Instruction 1425A. It SOP as the first step to solving a sticking valve. I’m curious why there was such a rush to pull the jug.

Thanks for that.

We were in a hurry to pull the cylinder because the rod was bent.  We expected all kinds of scary things.

image.thumb.png.efc48e6f45e0d3bc0f4d7f71bfb56a29.png

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1 hour ago, ArtVandelay said:

Do you have JPI fuel flow, it’s helpful to add that to the graph?

FWIW, many run LOP and go well past TBO...myself included.

 

Tom

Sadly, no.  I have the original Shadin FF computer and it is flaky.  But by my back-calcs, I cruise at about 12 gph ROP and 8.5-9 gph LOP.

I plan on sending my EDM-700 back to JPI to get the FF option and removing the dying Shadin. 

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2 hours ago, FlyBoyM20J said:

Thanks for that.

We were in a hurry to pull the cylinder because the rod was bent.  We expected all kinds of scary things.

image.thumb.png.efc48e6f45e0d3bc0f4d7f71bfb56a29.png

Don’t know how I missed the mention of the bent rod... disregard.

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21 minutes ago, FlyBoyM20J said:

Thanks for that.

We were in a hurry to pull the cylinder because the rod was bent.  We expected all kinds of scary things.

image.thumb.png.efc48e6f45e0d3bc0f4d7f71bfb56a29.png

Sadly it could have been fixed without pulling the cylinder.

Clarence

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1 minute ago, M20Doc said:

Sadly it could have been fixed without pulling the cylinder.

Clarence

I would love to hear more!  I was anxious to inspect the cam lobe.

Also, I suppose now that I know where I'm sending the cylinder for repair, I need to source a rod, tube, and whatever portions of the tappet mechanism might have been compromised by this event. 

I know there are different rod lengths.  Is it safe to assume that the exhaust valve rod is the same length as the intake rod? 

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22 minutes ago, Shadrach said:

Don’t know how I missed the mention of the bent rod... disregard!

I didn't mention it.  Initially, I didn't want to bother everyone with my problem in this thread, but I'm awfully glad for the interest and advice.

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3 hours ago, M20Doc said:

Sadly it could have been fixed without pulling the cylinder.

Clarence

As an A&P myself, I have to admit that one look at that bent pushrod and tube made me say "that cylinder has to come off."

Clarence- @M20Doc- your comment really made me stop and think about why, and I'd like to learn more.  So let me see if my thinking is correct:

- Just because the valve stuck and the rod bent, that doesn't mean that any damage was done to either the valve or the cylinder/piston

- Borescoping the cylinder through the spark plug holes will identify if any damage was done

- Using the Lycoming SI to push the valve into the cylinder, ream the exhaust guide, and the rope trick to reinstall the valve will identify if any damage was done to the valve or cylinder head

- Assuming the pushrod isn't bent so bad that it can't be removed, replacement shouldn't be too difficult

It sounds like the hardest part would be determining the correct pushrod length

Is that about right?  Thanks.

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1 hour ago, Andy95W said:

As an A&P myself, I have to admit that one look at that bent pushrod and tube made me say "that cylinder has to come off."

Clarence- @M20Doc- your comment really made me stop and think about why, and I'd like to learn more.  So let me see if my thinking is correct:

- Just because the valve stuck and the rod bent, that doesn't mean that any damage was done to either the valve or the cylinder/piston

- Borescoping the cylinder through the spark plug holes will identify if any damage was done

- Using the Lycoming SI to push the valve into the cylinder, ream the exhaust guide, and the rope trick to reinstall the valve will identify if any damage was done to the valve or cylinder head

- Assuming the pushrod isn't bent so bad that it can't be removed, replacement shouldn't be too difficult

It sounds like the hardest part would be determining the correct pushrod length

Is that about right?  Thanks.

Straightening the pushrod once removed is no great challenge.  I’m not saying it should be reused but it can be straightened to get the correct dimension. I’ve done this with motorcycle pushrods and actually reusd them with success. Process involves a piece of scrap lumber with a hole drilled slightly larger than the push rod (wood should be large enough to secure at least an inch thick and in robust condition).  The pushrod is placed in the drill chuck and passed back-and-forth through the hole while being turned it at high-speed . After the first few passes you pass it through with light side pressure in one direction. It’s amazing how straight you can get them using this method. Again I’m not suggesting anyone reuse a rod. Most metal rods can be straightened this way

Edited by Shadrach
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3 minutes ago, Shadrach said:

Strairening the pushrod once removed is no great challenge.  I’m not sync should be reused but it can be straightened to get the correct dimension. I’ve done this with motorcycle pushrods and reusd them with success. Process involves a piece of scrap lumber with a hole drilled slightly larger than the push rod (wood should be large enough to secure).  The pushrods is placed in the dril chuck and passed back-and-forth through the hole. After the first few passes you pass it through with light side pressure in one direction. It’s amazing how straight you can get them using this method. Again I’m not suggesting anyone reuse a rod. Most metal rods can be straightened this way

I'm glad I decided to wait before I sent this stuff off until more MS comments.  David Jewell asked me to include the bent pushrod when I send the cylinder.  I think that I'll try to straighten it and measure it first, though.

image.thumb.png.ba09f1a708e5addb3fee11ac8ea08e36.png

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5 minutes ago, FlyBoyM20J said:

I'm glad I decided to wait before I sent this stuff off until more MS comments.  David Jewell asked me to include the bent pushrod when I send the cylinder.  I think that I'll try to straighten it and measure it first, though.

image.thumb.png.ba09f1a708e5addb3fee11ac8ea08e36.png

That looks like it can be straightened. Since David is doing the work I would ask him first. Let us know how it shakes out

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Just now, FlyBoyM20J said:

I have access to this thing in the back room at work, so I bet I can make something work.

image.thumb.png.318c8713e5db88206f21fa2c4954301c.png

That’s a nice piece but I’ve never straighten the pushrod with the drill press. It goes without saying that if you’re going to attempt this do you want to protect the end that goes into the chuck. The rod will vibrate a lot. I know you don’t have anything to lose with regard to that rod but I would still call David first.

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1 minute ago, Shadrach said:

That’s a nice piece but I’ve never straighten the pushrod with the drill press. It goes without saying that if you’re going to attempt this do you want to protect the end that goes into the chuck. The rod will vibrate a lot. I know you don’t have anything to lose with regard to that rod but I would still call David first.

I have a hand drill and can do it that way with the wood die held in a vise.  Might be a better idea given how bent the thing is and I'm not sure the lathe or the drill press can be slowed down sufficiently.  But it is a handy machine.

I'll call David first.  Maybe he prefers to straighten it and measure it himself.  I just need to get a replacement, so it's all good either way.

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I believe there is a spec for the valve’s lift... that would directly supply/correlate the answer to what the length of the rod should be...

bending and unbending a rod should cause interesting metallurgy challenges... related to work hardening.  In the event of one being re-used (motor cycle) there is probably a heat treatment step to be used for relieving any internal stress that got induced...  keep in mind, the yield strength has been exceeded... hence the permanent change in shape.

See if you can get a pic of where the valve and piston met... the soft aluminum piston crown may have a half-moon shaped dent in it...

Apparently, the material selection for the rod, protects the Cam on one end and the rocker arm as well...

PP thoughts only, not a mechanic...

Best regards,

-a-

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9 minutes ago, carusoam said:

I believe there is a spec for the valve’s lift... that would directly supply/correlate the answer to what the length of the rod should be...

bending and unbending a rod should cause interesting metallurgy challenges... related to work hardening.  In the event of one being re-used (motor cycle) there is probably a heat treatment step to be used for relieving any internal stress that got induced...  keep in mind, the yield strength has been exceeded... hence the permanent change in shape.

See if you can get a pic of where the valve and piston met... the soft aluminum piston crown may have a half-moon shaped dent in it...

Apparently, the material selection for the rod, protects the Cam on one end and the rocker arm as well...

PP thoughts only, not a mechanic...

Best regards,

-a-

In this video on rebuilding the IO-360 (should be linked to the correct time for this section), they seem to suggest that rods of different lengths might need to be tried empirically in order to get the correct fit as referenced by a go-no-go feeler gauge.  I guess my worst-case situation is that I must buy 4 different rod lengths and try them, but then I'd also need the GnG gauge.

I've attached a picture of the piston face, as well.  I'm not sure I see any unusual marks.

image.thumb.png.f1bbe0b835456aa125784ed3f6c0fb95.png

 

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Just pressed out the wrist pin so now the piston is free.  Picture below.  It's easy to see the point where it impacted the exhaust valve now.

I also inspected the bent rod a bit more carefully and it has numbers stamped on it.  I hope this enough to find a replacement.

15F19957-57

ON972

31-97

This seems to be it!

http://www.aircraftspecialties.aero/push-rod-assy-15f19957-57/

 

image.thumb.png.ebf50911b1493e7fb045c345a88a9fd9.png

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10 hours ago, FlyBoyM20J said:

I would love to hear more!  I was anxious to inspect the cam lobe.

Also, I suppose now that I know where I'm sending the cylinder for repair, I need to source a rod, tube, and whatever portions of the tappet mechanism might have been compromised by this event. 

I know there are different rod lengths.  Is it safe to assume that the exhaust valve rod is the same length as the intake rod? 

A simple sticking valve can be repaired with the cylinder in place using the “rope trick”. The push rod and shroud tube are easily removed or installed while straight, so a bent one will be easy to removed and discarded, a new one is easy to install.  

Assuming that the cam follower was not damaged when the push rod bent, and that the valve and piston show not contact, there is no need to pull the cylinder other than for curiousity.  With the push rod removed you can do a compression check to confirm valve seating/ sealing.

Once the valve guide is reamed and the valve and springs reinstalled, do another compression check to confirm valve seating.

Push rods come in different lengths to get the dry tappet clearance correct, you won’t know which you need until re assembling the rocker arm.  If the valve or seat are reground, tappet clearance will be affected.

Clarence

 

 

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3 hours ago, M20Doc said:

A simple sticking valve can be repaired with the cylinder in place using the “rope trick”. The push rod and shroud tube are easily removed or installed while straight, so a bent one will be easy to removed and discarded, a new one is easy to install.  

Assuming that the cam follower was not damaged when the push rod bent, and that the valve and piston show not contact, there is no need to pull the cylinder other than for curiousity.  With the push rod removed you can do a compression check to confirm valve seating/ sealing.

Once the valve guide is reamed and the valve and springs reinstalled, do another compression check to confirm valve seating.

Push rods come in different lengths to get the dry tappet clearance correct, you won’t know which you need until re assembling the rocker arm.  If the valve or seat are reground, tappet clearance will be affected.

Clarence

 

 

Thank you, Clarence!

If I understand this correctly, a different length push rod than the original might need to be used any time a valve or seat is reground, regardless of whether the original rod was damaged.

In my case, all of that is up for grabs, so to do this properly, I should buy a few sizes of pushrod, and test for min/max as found in SSP-1176-4.  For IO-360, we'd be Chart S, so it looks like min is 0.028 and max is 0.080... inches, I assume.

 

image.thumb.png.d8993751789fb0781a15825455e34e37.png

 

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1 minute ago, FlyBoyM20J said:

Thank you, Clarence!

If I understand this correctly, a different length push rod than the original might need to be used any time a valve or seat is reground, regardless of whether the original rod was damaged.

In my case, all of that is up for grabs, so to do this properly, I should buy a few sizes of pushrod, and test for min/max as found in SSP-1176-4.  For IO-360, we'd be Chart S, so it looks like min is 0.028 and max is 0.080... inches, I assume.

 

image.thumb.png.d8993751789fb0781a15825455e34e37.png

 

When you get your cylinder back you could ask Jewel to send you a few push rods of the more popular lengths.  Once you reinstall the cylinder and get the clearance correct, ship the unused push rods back to him.

Clarence

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4 hours ago, M20Doc said:

Assuming that the cam follower was not damaged when the push rod bent, and that the valve and piston show not contact, there is no need to pull the cylinder other than for curiousity.  With the push rod removed you can do a compression check to confirm valve seating/ sealing.

 

I don't know what circumstances lead to a bent push rod, but it seems like it must be severe.  I would like to understand what has happened here.

Would this occur only if the valve did not open for some reason?  In which case, instead of concerns about compression, you would need to check the linkage between cam and valve to see what was binding?  Failed bearing/bushing of the rocker?  The valve itself welded in its guide or stuck to the valve seat?

The OP states that contact indications on the piston face exist.   This means the exhaust valve was stuck open, correct?  This should lead to a push rod flopping around, not getting caught between the cam lobe and an immovable valve.  

-dan

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15 hours ago, M20Doc said:

Sadly it could have been fixed without pulling the cylinder.

Not to question the master, but I had a bent rod recently (must be going around) and it tore up the rocker arm, cylinder had to go.

I did have a fun time (literally!) fixing it...learned a sh*tload about the engine.

Had a colossal scare when we thought the cam had a crack, turned out to be oil sheen. Don't ask.

Now she is running like a champ. Happy ending!

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1 hour ago, Dan at S43 said:

I don't know what circumstances lead to a bent push rod, but it seems like it must be severe.  I would like to understand what has happened here.

Would this occur only if the valve did not open for some reason?  In which case, instead of concerns about compression, you would need to check the linkage between cam and valve to see what was binding?  Failed bearing/bushing of the rocker?  The valve itself welded in its guide or stuck to the valve seat?

The OP states that contact indications on the piston face exist.   This means the exhaust valve was stuck open, correct?  This should lead to a push rod flopping around, not getting caught between the cam lobe and an immovable valve.  

-dan

When the valve gets really stuck in the guide, something will give.  The push rod is the weakest link in the valve train so it bends, in unlucky cases the valve lifter body is damaged.

When the valve sticks open the piston crown drives the valve toward the closed position, all of this happens in the blink of an eye.

Clarence

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One reason for a stuck valve...

  • exhaust valves and guides are around the hottest part of the engine... and there is no temp sensor there to measure it.
  • They are normally cooled by an ample supply of engine oil flow...
  • The temperature that oil degrades at is well below the EGT that is heating the valve....
  • So... the oil needs to keep moving...
  • High CHTs And poor cooling can exacerbate this challenge....
  • Oil that degrades in these tight-ish channels can turn into solid carbon chunks.
  • Carbon chunks have a tendency to reduce the oil flow to the area.
  • Slower flow results in longer residence times of the oil in that really hot location.
  • Longer residence at high temps leads to more degradation and carbon deposits.
  • enough solid carbon in the valve guide, not enough oil flowing through, high power settings, changing temps during an initial climb... are high stress times for an engine...

The cool thing about an engine monitor...  the sticky valves leave a good fingerprint long before they become a stuck valve...

The challenge of not having an engine monitor... the pilot might not be skilled enough to recognize the early signs of sticky valves...

When the valve crashes into the piston... it can stop operating... valve not closed, no compression, no power for that cylinder... lots of vibration, plenty of noise, and about 50 less HP being produced... right when the pilot is calling for maximum power...

Great pics, FlyboyJ! For anyone not seeing the point of contact... click on the pic to have it show up in HD. The mark is in the area where the piston is carved out for where the valves normally are... not enough room to be stuck open.

Great support, M20Doc! It is great to have your experience shared here.

Go MS!

Best regards,

-a-

 

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