Rocker Arm/Valve Wear?

iflyvfr

iflyvfr

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Greg
Yesterday we installed the pushrod kits from Real Gaskets. Took two of us about 7 hours from start to finish to do the left side.

In the center cylinder, after removing the pushrods we found this:

https://drive.google.com/file/d/0BxRCx-rLC62NclFJMmVsTG1FLURnd2Jsd2NOOUdKcUhYZlg4/edit?usp=sharing
https://drive.google.com/file/d/0BxRCx-rLC62NSHk5OWpvOElHMHVCM3pkOG82dmJFVUZUdWVj/edit?usp=sharing

The rocker arms and the valves have visible wear on them. The consensus is I have a new cylinder in my future as I'm likely to burn a valve and fail a compression check.

What causes this and is there a cure beyond a new cylinder? It looks like the damage is done so I'm just going to need to monitor it from here out.
 
I would be checking the oil flow through the lifter and up the push rod. It looks like no oil is getting to it.
 
Henning said:
I would be checking the oil flow through the lifter and up the push rod. It looks like no oil is getting to it.
Click to expand...

Interesting. The valve cover had oil in it, but I didn't notice how much relative to the others.
 
Run it with that valve cover off and see if it squirts oil on both sides. Also compare collapsing that lifter to another.
 
iflyvfr said:
Both sides. Could the rods be mis-sized and slapping?
Click to expand...

Easy enough to check. BTW, those are Pushrods, in engine parlance rods connect the piston to the crankshaft. Roll it to TDC compression and see if you have a bunch of slack. Did you do a lifter collapse test?
 
BTW, I would not continue operating in that condition, you have a good chance of multiplying your repair costs exponentially if that goes to failure. Dropping a valve can lunch an entire engine.
 
Henning said:
Easy enough to check. BTW, those are Pushrods, in engine parlance rods connect the piston to the crankshaft. Roll it to TDC compression and see if you have a bunch of slack. Did you do a lifter collapse test?
Click to expand...
We did not but we certainly will. Thanks for the clarification re: pushrods. I don't wish to cause confusion in my attempt to be succinct.

I do have another cylinder bathed in LP3 waiting to go. My concern is that if the pushrods are undersized I don't want to reuse what I have. I will talk to my mechanic and see what he says. I'm sure a call to G&N will clarify things but certainly I'm looking at new rocker arms.
 
iflyvfr said:
We did not but we certainly will. Thanks for the clarification re: pushrods. I don't wish to cause confusion in my attempt to be succinct.

I do have another cylinder bathed in LP3 waiting to go. My concern is that if the pushrods are undersized I don't want to reuse what I have. I will talk to my mechanic and see what he says. I'm sure a call to G&N will clarify things but certainly I'm looking at new rocker arms.
Click to expand...

My concern is still in the lifter. I wish I was there to roll it.
 
iflyvfr said:
This part?
https://www.aircraft-specialties.com/hydraulic-unit-646846/

I'll mention your concern as well, as I'm now way outside my mechanical comfort zone. :)

Regardless, its a great reason why owner-assisted work is so rewarding. I get to learn the entire time and I know what I'm facing.
Click to expand...

Yep, that's the part. So when you ran it, you got good oil flow through both rockers right? If it squirted enough to make a mess, that's good enough to not be the cause of what I see. What I'm wondering is if the lifter is pumping out too high or has a piece of crap lodged in it that is causing it to bottom out the valve. Does that pushrod show any sign of bending or compression stress? If it's putting oil to the valve, that is one weird deal.
 
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Geico266 said:
I would not fly knowing what I see.
Click to expand...

Yeah, definitely not, only run it for testing purposes.

My next step would be collapsing the lifter and disassembling the spring and keeper to more closely inspect the hardware for any indications of what is happening, especially signs of heat.
 
Those valves have been hammered by too much valve lash. Either the lifters were deflated or the pushrods were too short. The other possibility is that the intake and exhaust rockers were switched. There is nothing to do now but pull the cylinder.
 
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Silvaire said:
Those valves have been hammered by too much valve lash. Either the lifters were deflated or the pushrods were too short. The other possibility is that the intake and exhaust rockers were switched. There is nothing to do now but pull the cylinder.
Click to expand...

Yep, and lifters. I'd still want to find out why it happened. Normally this type of stuff doesn't fail unless there is an oiling issue, that's what concerns me. How tough is it to pull the gallery plugs and flush the oil galleries?

Here's a question, have you cut open the filter or been doing oil analysis?
 
It can be caused by improper maintenance. It's difficult to determine from a couple of fuzzy pictures but if you look closely at the first one he is holding up what appears to be an exhaust side rocker arm in front of the intake valve. If that's the way it was assembled then the rocker arms were swapped. That is not so easy to do because well, it just looks totally wrong when you assemble it like that, but it is possible.
 
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I had to think for a moment, but that rocker arm is held upside down. The wear you see on the face is from the pushrod end striking it. The pushrods themselves look to be in good shape, not bent to my knowledge.

One idea that was thrown out was that they are of the incorrect length (short). If I sent it out for OH, can I get correctly sized pushrods put in (if that's found to be the issue)?

I've not cut the oil filter, but my mechanic does at annual and no mention of metal found. It's time for a change, so I can do both although I suppose the analysis is moot now.
 
iflyvfr said:
I had to think for a moment, but that rocker arm is held upside down. The wear you see on the face is from the pushrod end striking it. ...
Click to expand...

No, it is flipped left to right, not upside down and the wear is from the rocker perch contacting the valve stem. The pushrod fits into the cupped end at the bottom of the picture. If you look closely you can see how the worn area is off centered and that the center part of the rocker arm, through which the shaft passes is slightly tapered on one end. That end should be on the outboard side when assembled and if that is indeed the rocker arm that you removed from the intake valve it looks to be the wrong one. It looks like an exhaust rocker arm.

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iflyvfr said:
One idea that was thrown out was that they are of the incorrect length (short). If I sent it out for OH, can I get correctly sized pushrods put in (if that's found to be the issue)?
Click to expand...

There are several "standard" lengths of pushrods. You simply swap 'em in and out until you find the right length for a particular valve/rocker/cam lobe combination.
 
Silvaire said:
No, it is flipped left to right, not upside down and the wear is from the rocker perch contacting the valve stem. The pushrod fits into the cupped end at the bottom of the picture. If you look closely you can see how the worn area is off centered and that the center part of the rocker arm, through which the shaft passes is slightly tapered on one end. That end should be on the outboard side when assembled and if that is indeed the rocker arm that you removed from the intake valve it looks to be the wrong one. It looks like an exhaust rocker arm.
Click to expand...

Ok, thanks for setting me straight, this is all learning for me. Obviously this is way beyond my pay grade so thanks for not flaming me.

I went back and looked at the two pics again. Clearly the markings between the valve and the rocker arm match up perfectly. This was the only one of the three that didn't fight us while we pulled and then reinstalled the rocker arm pin, so it doesn't seem possible that the rocker arms were reversed. Or that pin would have never gone back in, much less easily, right? Perhaps its the angle of the picture?

Here's another look with all three together. You can see the witness marks and how they line up.
 

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As I said, I can't tell anything for certain from the pictures and I'm not saying this is the cause of your problem but it's possible. I just know that the intake and exhaust rocker arms are different part numbers, If you look at the pictures on this eBay ad you can see better what I mean about the taper and if you read the description it explains a bit about the interchangeability and non-interchangeability of the rocker arms.

$_12.JPG
 
Looks like the pads on the rocker arms were dressed crookedly at last overhaul.

We had that happen on a club '67 172 (O-300D) at 60 hrs SMOH. The shop discovered it on a cylinder assembly we had removed due to a leaking exhaust valve. The voluntarily reground all of the rocker arms correctly & we reinstalled same. That engine went at least another 1700 hrs with no problem.
 
nrpetersen said:
Looks like the pads on the rocker arms were dressed crookedly at last overhaul.

We had that happen on a club '67 172 (O-300D) at 60 hrs SMOH. The shop discovered it on a cylinder assembly we had removed due to a leaking exhaust valve. The voluntarily reground all of the rocker arms correctly & we reinstalled same. That engine went at least another 1700 hrs with no problem.
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Same engine here on a '66 G model. So I called G&N today and when we pull the jug he wants the rocker arms to see if they can be fixed up or will need to be replaced.

Do you mind me asking which shop you used?
 
It was 40 years ago - Jack Sandburg at Metal Masters. They were a local engine rebuilder that Reno-raced modified P-51s (was it Strella?). One of them was killed near Pierre SD when the highly modified engine failed.

As I recall, it was no big deal to have the profile of the rocker arm pads reground again. They were the ones that spotted the sidewise loading when the jug assy was brought to them.
 
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