> Whoops. I guess I'm a bit too literal. When you say "lost a lobe," I
> assumed that the specs on the lobe itself ground beyond
> tolerance. Couldn't
> figure the talk on a soft lifter, since to overly wear a cam lobe
> would have
> to mean a tight, hard lifter.
Not true at all. I don't know the exact process involved, whether it's just
the soft lifter losing it's finish and grinding away the cam as Irv says, or
if there is actually galling (a kind of microscopic spot welding) involved,
but I do know that soft lifters spell death for a cam lobe.
Of course, the lifter may wear too, but you generally don't care about that
unless it actually wears through or breaks. Otherwise, any wear will be
taken up by the normal lash adjustment. However, the cam lobe only wears on
the tip, so any wear at this point means less valve lift and lower overall
performance.
Cams involve very high pressures, higher than (for instance) rod bearings,
because the contact between the lobe and the lifter is (theoretically)
infinitely small. Of course it can't be infinitely small, so there is some
deformation involved, and strange things happen when you start deforming
steel on a regular basis.
I've even read of a bad fuel pump causing the pump lobe on the cam to "go
away" (although not on a TRactor motor).
Randall
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