Logbook Page Removed and not Disclosed - Criminal Misrepresentation?

[Bolter]

1 hour ago, MikeOH said:

Not an A&P, so maybe one here can explain the different ways it is possible to bend a pushrod on a Lycoming.

Short of a badly stuck valve: cam pushes on lifter, pushes on pushrod, pushes on rocker, pushes on STUCK valve that doesn't move...pushrod is weakest link and bends, I don't see how it can happen.

Hydraulic lifters are designed to take up ALL clearance in a running engine, so even if the pushrod is so long as to bottom out the lifter to the point the valve is on the ragged edge of opening (if the valve was actually held open the engine would barely/not run) I don't see how the pushrod can get bent. IOW, even in that scenario I don't see how the valve is going to hit the piston, or fully collapse the valve spring to where it binds.

Maybe the question is: are valves fully open when the piston is at TDC, and what is the clearance between the two, if so.  A too long pushrod would need to open the valve past that clearance.  Then, we are back to how did the engine run for a minute, let alone 700-800 hours???

What about a lubrication issue?  What gets the oil to heads, and is it flowing properly or blocked?  Is it a common feed to all the heads, or each has its own feed?  If the hydraulic push rod is in constant contact with the valve, and there is not the right amount of oil getting there, it become metal on metal instead of the proper oil film.  Similar to what happens with the cams from dry starts.  Or possibly if the CHT's are too high, the oil may be burning off instead of lubricating.  Though that would leave coking indications, I think.  

Just thoughts on a different direction that creates wear at that interface.  The push rod has equal force on the cam as the valve, but only one end is wearinng.  The cam is constantly rotating, and the valve is pulsing, so the motion and contact patch area are different, even if the forces are the same.  

-dan

[Utah20Gflyer]

Wow, this is quite the situation.

rockers arms are damaged ?

pushrods are all bent?

pushrods that came out won’t go back in?

you are being told the case has been milled beyond limits but the accessory case still fits?

but the engine ran like that for 800 hours?

I would say the next step is certainly a second opinion.  No knock on the current mechanic but the confusion seems to be multiplying.  I think an engine shop like you are talking about is a great idea.  
 

[ragedracer1977]

I just can’t comprehend how anything fit in the crankcase if it’s over milled by 30-40 thousandths.  How did the bearings install? How did the accessory case install? How did the sump pan line up?  
 

 

[OR75]

I had to go back to the initial post ... so the compressions were good but they decided to change the rockers ?

[M20GforMe]

1 minute ago, OR75 said:

I had to go back to the initial post ... so the compressions were good but they decided to change the rockers ?

Yup. They did tell me there was some marring on them and recommended that they get replaced so I had given them the thumbs up, not having known any better at the time…

[N201MKTurbo]

I remember about 25 years ago I had a rocker with a chip on its face. I took it to the local engine shop to get a new one. I showed it to the owner of the shop and he said “you don’t need a new one” then took it to his grinder and ground the face down till the chip was gone. He handed it back and said “here ya go” I put it back in the engine and it never gave me any trouble.