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-   -   Lycoming o-320 Valve train noise?? Watch video (https://vansairforce.net/community/showthread.php?t=138320)

William 05-28-2016 02:39 PM

Lycoming o-320 Valve train noise?? Watch video
 
Hello a little background first. The engine does not have mags, it has dual pmags so I know it's not the impulse coupler. I've overhauled this engine last year and had all internal parts yellow tagged and assembled the engine with new Lycoming cylinder assemblies. I'm having a valve train noise that I can't track down. Don't know if this is normal or not and only noticed it when I pulled my plugs out to change them and rotated the prop. Since the video I've pulled the pushrods and the hydraulic lifters out and the noise has stopped so I know it's coming from the valve train. I've pulled the cylinders today to check the cam and tappet bodies and they are perfect as would be expected from a engine with 1-2 hours of run time. Any idea?

Thanks
Bill

https://m.youtube.com/watch?v=FC-_le...ature=youtu.be

Ironflight 05-28-2016 03:11 PM

Interesting noise, but not sure I know what it is.

Did you check your dry tappet clearance for all pushrods?

William 05-28-2016 03:19 PM

Quote:

Originally Posted by Ironflight (Post 1082897)
Interesting noise, but not sure I know what it is.

Did you check your dry tappet clearance for all pushrods?

Hi Paul thanks for the response. Yes all dry tappet clearances were checked and were in the middle of the allowable range.

Thanks
Bill

rv4ross 05-28-2016 05:07 PM

I assume you have not run the engine yet, so, Have you spun the engine over enough so as to get oil pressure? Could be that the lifters have not pumped up yet. You could also get a mechanics stethoscope and have someone spin the prop over as you have been doing and listen at the crankcase end of the valve train to see which end the noise is coming from. Still betting the lifters have not pumped up.

Ross Scroggs
Locust Grove, GA.
A&P
RV-4 Finishing kit

William 05-28-2016 05:34 PM

Quote:

Originally Posted by rv4ross (Post 1082925)
I assume you have not run the engine yet, so, Have you spun the engine over enough so as to get oil pressure? Could be that the lifters have not pumped up yet. You could also get a mechanics stethoscope and have someone spin the prop over as you have been doing and listen at the crankcase end of the valve train to see which end the noise is coming from. Still betting the lifters have not pumped up.

Ross Scroggs
Locust Grove, GA.
A&P
RV-4 Finishing kit


Thanks for the response Ross. The engine has been run several times since being overhauled last year. I have not flown the plane yet though. Preparing for first flight and this is one of the last issues. The engine is very quiet when running. Meaning no noises out of the ordinary are heard. I only found this noise by accident during plug change.

Thanks
Bill

Robertc 05-28-2016 07:04 PM

Are the caps on the exhaust valve under the rocker arm?

William 05-28-2016 07:55 PM

Quote:

Originally Posted by Robertc (Post 1082935)
Are the caps on the exhaust valve under the rocker arm?

Yeah the caps are in place on the top of the exhaust valve stems.

Thanks
Bill

William 05-28-2016 07:58 PM

Can anyone confirm for certain that this noise is not normal? Anyone have there cowling off that could pull the top plugs and rotate there engine a few turns and see if it makes the same noise?

Thanks for all the help
Bill

Steve Melton 05-28-2016 08:42 PM

I don't remember hearing those noises when rotating my engine to check mag timing. If I had I would have remembered.

lr172 05-28-2016 10:37 PM

That is Cam whip. I noticed it after I rebuilt my engine and spent two days trying to figure out what I did wrong. Two of the cam lobes operates two different valves on opposite sides of the engine. At a certain point in it's (the cam) rotation, the opposing forces from the valve springs transfers from one valve train to the other. At this moment the cam trys to reverse direction and gives up it gear lash and causes the click. It is insignificant and unnoticeable at any meaningful RPM, but quite noticeable when turning by hand. As you showed in your video, it always happens at the same place(s).

Larry


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