> Any
> way you draw it, it comes out the same--a dome moves the contact point
> towards the center compared to a flat lifter.
That's true, but if the cam lobe is tapered (as it should be for domed lifters),
moving the contact point in from the edge is a good thing.
> Given inertial forces and heavy springs it could be a lot of thrust.
Do the math, I think you'll find it isn't much at all. The vertical force gets
multiplied by the sine of the lobe taper angle, which is down around .005 or so
(.002" or .003" across a .500" lobe), so 500 pounds vertical only causes 2.5
pounds horizontal. Make it 2000 pounds, we're still only talking 10 pounds of
thrust. Some engines actually use the force to pull the cam against it's thrust
bearing ... there's nothing else to hold it there (which is why something needs
to be added when converting to roller lifters).
> If your cam is shiny all the way across the face it either isn't
> ramped or the ramp has worn off.
Or the ramp & lifter face deflect enough to cause contact all across the face.
Remember these surfaces are not perfectly rigid, they do flex a bit. My stock
Triumph cams are shiny all across the tip of the lobe, but it can be seen that
the contact is heavier to one side. The flanks only show contact to one side.
> You pays your money and you takes your choice.
Yup.
> I just can't see how it helps
> a TR motor in any way.
Ask yourself what happens if a lifter bore happens to be out of true by .001" or
so. With flat lifters and untapered lobes, the edge of the lobe will be
carrying all the force. With domed lifters and tapered lobes, the contact
pattern is off slightly, but still not at the edge.
Randall
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