We have discussed this several times. It hard these days to talk about
auto companies being American or European, since they are all
multinational, with engineering and manufacturing in many countries. I
have attached a page out of a Ford Motor Co. design manual from the
1980's. That's 30 years ago, but the laws of physics haven't changed.
Chris is right that Triumph did not put a taper on their cams, but
Austin/MG did. I don't know about others first hand, but engine builders
I've talked to say a crowned lifter is the norm. Glen has more
experience than I do, but I have taken a few TR engines apart and have
seen a few where the lifter had obviously not been rotating.? It is true
that the lowest stresses will occur if the lifter is flat and the cam
lobe is flat and they mate perfectly, but it is less likely to rotate.
Also, I'm told that it is virtually impossible to achieve perfect
alignment because the lifter will be canted in the bore or the bore may
not be perfectly perpendicular, or the cam lobe might have a slight
taper. Then you end up with the far right picture with infinite surface
stress at the contact point. We are talking about a radius of 50 to 100
inches on the lifter and a taper of maybe 0.001 inches across the lobe.
?- Larry
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