Jim and List,
I'll have a go at #4, as this one is still open. I hope the explanation is
clear, I'd rather make a drawing!
Let's look from a theoritical point: a roller rocker has a roll at the
contact to the valve stem whereas the standard rocker has a polished
surface. When moving a valve from the closed to the open position, the
rocker arm performs a section of a circle around the rocker shaft. The roll
will move downwards and pushing open the valve and rotate a bit while doiing
so. The rotation of the roll ads a little to the radius thus slightly
increasing the ratio and therefore open the valve further. For the standard
rocker, the distance from the rocker shaft to the valve stem in theory
remains unchanged.
I must ad that in practice, the exact shape of the standard rocker does make
a difference, and also that the extra amount of valve opening with a roller
rocker is more of a theoretical nature.
Is this what you're after, Jim?
Marc Nederkoorn
The Netherlands
'74 TR6 (almost standard engine, just a warm cam and increased compression)
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