I can follow you if the lobe is not flat grindet and is tappered. That would
make sense to dome the lifters because they would run on the edge. After your
information I from now on test each cam if it has tapered lobes.
Thanks
Chris
----- Original Message -----
From: Fubog1@aol.com
To: BillB@bnj.com ; fot@autox.team.net ; triumph_marx@freenet.de
Sent: Friday, January 06, 2006 9:48 PM
Subject: Re: Tappet talk
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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