His math is wrong. The effective diameter of a .842 lifter with a .015 chamfer is gonna be .842-.0106x2 or .821 because the .015 is the long side of that right triangle (you need to apply the Pythagorean theorem) and that gives you a base of .0106. Those look to be hack angle grinder regrind returns. The wear pattern on a break in only Melling slant solid lifter was only .025 wide so that means the lifter crown and the taper of the cam were not equal (to no suprise) as both will lap together over time to the ability of both metals to conform. Remember that you need a certain interference to rotate the lifter and I would certainly want the lifter to rotate over having a perfect 1/2 face wide wear pattern as that larger contact pattern will possibly (doubtful) come with the break in. Im not sure why the lobe width is even a factor as its never gonna need to be more than half the lifter face and even that is a stretch. Interesting vid none the less.
