In a message dated 1/6/2006 3:02:04 PM Eastern Standard Time, BillB@bnj.com
writes:
I can't visualize how doming would help
rotation unless it was moving the contact patch off center in a cam/lifter
pair where the cam lobe was centered over the lifter.
Bill-
The cam lobe is indeed off center from the tappet centerline.
FWIW I have info direct from Piper (some years ago) re an inquiry I made, at
the time they ground their lobes in at 5 minutes, don't have spec for their
tappet radius. They generally show up as not quite perfectly flat when
checked with a straightedge, it's a VERY SLIGHT"dome".
I agree that there are many different opinions on these things but we also
have have to realize that we're dealing with the basic Triumph pushrod engine,
modern OHC bucket & roller types are obviously different.
"I have about 30 lifters. All domed ones have pitting near the center of
rotation. The perfect flat ones didn't fail so far and have a smooth surface.
Everytime I install lifters I inspect the surface NOT to be domed."
Chris-
I cant't argue with someone elses good results. I too sometimes have the
pitting problems as you describe. Assuming that the tappet is hard & turning
properly, I've attributed that to an excess load issue & lube breakdown. The
cam
acceleration rate, weights, & spring pressures, etc are all variables here
of course.
Now, if Uncle Jack follows this thread, we might be in for another survey...
Thanks for the feedback,
Glen
(not a cam designer)
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