Well, drop the pan, and look for a lose rod bearing. becuasue that
material you are describing is the babbit material (soft) used in the rod
bearings, Also the Main and cam berings too, but they are less like to have
spun. You can probably locate the individual rod with the pan off, by reach
up and trying to twist each rod on the crank. You will probably find one
that is loser than the others. if you have the tools, remove the rob end
cap and inspect the bearing. You will find the it will look melted and
scored. In itself, not a real bad thing....Inspect the cank journal
closely, and all the way around. If it is smooth and polished with no
scoring of any kind anywhere, then make sure the oil passage is clear with a
thin wire. if all is well, then you can replace the bearing. If you have
micrometer, then check the journal diameter to see if the wrong undersize
bearing was used. (can happen!) the back of the bearing will indicate it's
undersize like (in inch unitis) .010, .015..etc..
As long as everything is OK other than the bearing itself, then you can
just replace it. The reason for the failure may elude you. if the correct
size was used, it can be dificult to determine the real cause. Be sure to
check ALL of the rods though. There may be more than one. If you have the
tools, you could also check the mains. bu remember, you will need to
retorque these all back to proper specs... if this engine is used for
normal operation and is not stressed in performance applications, then just
replace the bearing. If it is a high performance engine, then removal and
teardown may be required.
There is NO way to inspect the Cam bearings with out a disassembly...
Good luck !
Rich
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