I've talked to Steve at Integral cams also, nice guy. Triumph lifters
were originally flat, and many that I've taken apart show the lifters
were not rotating. As Greg Solow has dicussed several times, the lobes
on the Triumph cams are offset from the centerline of the lifter bores
in pairs. Most manufacturers use a slight crown on the lifter, i.e. a
50 to 100 inch radius, and a tapered lobe. The crown of the lifter
should be matched to the taper of the lobes and the offset in the lifter
bores so the contact patch will be off center but not on the edge. This
promotes rotation of the lifter and less wear.
When I've had lifters tested for hardness, they used a different
Rockwell scale to avoid putting a big dimple in the lifter. They have
conversion charts to go from one scale to another.
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