The not so flat lifter.

[88v8]

A question on another forum made me think; some of you knowledgeable chaps will know.

So-called 'flat lifters', generally have a slight radius.
Was this always so? If not when did the practice start?

Ivor

[Citron]

I was taught that they are cut on a 32ft radius.    I never tried to test that.  A flat lifter will wear quickly since it will not rotate.
Steve

[88v8]

AIUI it used to be normal practice that lifters were offset relative to the cam lobe. That's how they rotated. But the lifter was wide which increased valve train inertia. So then they were radiused and the cam was ground with a slight taper.
But when did that development become general ? Before WWII, or after?

Ivor