Cam Whip

[flinthillsflyer]

Has anyone heard of this phenomenon, "Cam Whip"? The only place I've seen this term used was in a thread on vansairforce.com. I'm having a similar issue with a field overhauled O-320. The "click" noise is coming from the cam/valve train when all the push rods are installed. The engine is still on the assembly stand and this "click" happens at 180 degrees of rotation every time. The assumption is this noise and issue will disappear once the lifters have been bled up upon the engine reaching normal oil pressure. Has anyone ever heard of this or have any information about this?

 

[flinthillsflyer]

http://www.vansairforce.com/community/showthread.php?t=138320

 

[alfadog]

Camshaft whip is a thing but not a static issue like you describe. It is dynamic and mostly an engine design issue from what I am getting.

 

[alfadog]

Sounds like an engine assembly issue to me. I would try to isolate which lifter is causing the issue, maybe with a stethoscope, then disassemble and replace the suspect lifter. Or you can put it all together, install it on the a/c and hope for the best.

 

[alfadog]

Looking at the Vans thread and the associated video, it looks like this is a known and OK? issue. So I stand corrected perhaps. That said, not sure "cam whip" is the right terminology as that seems to be a common term in engine design for a dynamic issue.

 

[Dan Thomas]

http://www.vansairforce.com/community/showthread.php?t=138320

Right answer, wrong term for it. He says:

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).

As a mechanic I've heard it often. Once the engine is running and lifters are full and the gear train wet with oil, there's no noise.