In a message dated 96-07-04 14:31:32 EDT, Jim Mellander wrote:
>I was wondering if it is permissable to grind down the tappets to acheive a
flat surface, or must they be replaced????
As a rule, the tappets start out with a slightly crowned surface on the end
that runs against the cam lobe. They are also located slightly off center
from the cam lobe. The combination of these two things causes the tappet to
rotate slowly and continuously.
As a result the cam lobe eventually wears to a slight down slope towards the
center of the tappet, the end of the tappet continues to wear to a crowned or
conical shape, and the tappet continues to rotate forever, minimizing the
overall wear and extending the life of the tappet and the cam lobe by
eliminating flat spots on both.
If you grind the tappet flat on the end and mate it to a new cam shaft, the
tappet will not rotate, will in fact soon wear an indentation matching the
cam lobe, and accelerated wear will ensue. Most likely the tappet and the
new cam will soon be totally trash, probably within 20,000 miles or so.
It is acceptable to put new tappets on an old cam, but never, never, never
try to use the old tappets with a new cam. Most new camshafts come in a kit
that also includes a new set of tappets.
If you think your labor cost is less than a new set of tappets, you can
regrind the tappets, but be sure to duplicate the original crown on the
contact end. It also wouldn't hurt to flame harden the contact end after
grinding. Personally I can't afford the regrind, as it does not compare
favorably with the cost of a new set of tappets.
Barney Gaylord -- 1958 MGA
Naperville, Illinois
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