Upon tear down of our 340 all the original rod and main bearings look pretty good as do the cylinder walls with no ridges and still a crosshatch. But a couple of cam bearings look like this; any ideas of the cause?
:wrenching:
I saw that same damage on a 400 once. Curious what people say. The 400 in question had been sitting for quite awhile.
I have never seen the babbit flake off like that... ever...
I would have to guess poor manufacturing for the bearing(s), or installation when tapping them in with incorrect size collet (or not using one)...?
The actual bearing surface doesn't appear to have had much gunch run through the babbit that's there...
Yes it is weird, I have never seen it before and as I said everything else looks good for being near 50 years old :notsure:
How is the rest of the bearings? This looks like insufficient oil flow to the bearing. The hole is aligned, but the gallery could be plugged. Mic the journal see if it was too tight. Is the material welded/stuck onto the journal?
I have also seen it before , but I don't have definate cause .
It is difficult to correctly Size cam brgs , when installed there are too tight so many machinists cut a sharp groove in an old cam brg surface to cut the brg surface for clearance , this still may not give enough clearance as it only removes enough to have zero clearance for oil . In theory you would not only need to cut the cam brg surface on the cam but raise the cut lip .001 to gain enough clearance in the brg for enough oil flow .
Basically I believe it is caused by the brgs being too tight even after being "sized" or clearanced
No the babbit is just "gone" and all the other engine bearings look pretty good as does the cam and crank.
Quote from: hanksemenec on May 21, 2020, 10:26:50 AM
How is the rest of the bearings? This looks like insufficient oil flow to the bearing. The hole is aligned, but the gallery could be plugged. Mic the journal see if it was too tight. Is the material welded/stuck onto the journal?
Quote from: Chryco Psycho on May 21, 2020, 10:31:28 AM
I have also seen it before , but I don't have definate cause .
It is difficult to correctly Size cam brgs , when installed there are too tight so many machinists cut a sharp groove in an old cam brg surface to cut the brg surface for clearance , this still may not give enough clearance as it only removes enough to have zero clearance for oil . In theory you would not only need to cut the cam brg surface but raise the cut lip .001 to gain enough clearance in the brg for enough oil flow .
Basically I believe it is caused by the brgs being too tight even after being "sized" or clearanced
:iagree:
I have seen it a couple times myself. I to believe it was from being to tight during assembly.
:bradsthumb: :bradsthumb: :bradsthumb: