What causes lifter failure on these motors? I have a 6.4 right now that I received already partially disassembled, and after removing a cylinder head I found 3 broken lifters (all intake side if I recall), a slightly bent push rod, broken lifter tray, and some evidence of a previously broken rocker arm on cyl 1 or 3. The head gasket shows no sign of failure, but cylinder number 3 was right full of oil. Not sure how it got there, there's appears to be no piston damage, and cylinder walls look pretty good. I hate diving into a job that someone else has already started, so im just looking for a little help on this one...