Golden Jubilee
Posts: 5177
Joined: Thu Nov 29, 2012 9:28 pm
Location: Lyman, IA
Re: Need Help Diagnosing Engine Knock
Rod/main bearings is likely the worse possible problem that could cause a knock, so I would want to eliminate that as a possibility as soon as possible. It would also be the hardest to repair if left to run until "un runable". If cought early and the reason remedied, the engine can be restored with new bearing of the same size.
An engine will run a long time with piston slap and have no real harm, but better to re size the piston early if you are going that route.
Some engines can feed oil to other locations from the cam bearings, and if they aren't orientated correctly can cause oil starvation down stream. However it is most often top end lubrication that is fed off the cam bearings.
It is also possible that poor mfg/ hardening of the tappet could be the cause and nothing about the rebuild could have caused the noise.
I think it will reach the point that dis assembly will be needed to nail it down and repair. Disappointing, but it may very well be no fault of anyone involved other than the mfg of the parts. It is rare, but not unheard of. I had to re-do one cyl on a K-19 Cummins due to inferior parts on that one "hole".