Hi,
A couple of days ago I described the method I called something like
the "symmetrical center roll over method" for selecting push rod length for
best valve train geometry. Well, even though this method is described by
several leading cam component manufacturers including the one I bought my push
rods from I now believe that this is not the correct way to select push rod
length.
I did some research and it looks like what you really want is for the roller
tip to start on the intake side of the center line of the valve stem tip, roll
over to the same distance on the other side of the centerline at half lift and
then at fully open roll back to the same tip position as when the valve was
fully closed.
This makes sense because this will produce the smallest contact area centered
about the center of the valve stem centerline and therefore will reduce wear on
the guides. Also if you take a look at the geometry involved you will see that
it is technically impossible to achieve total symmetry about the valve stem
centerline using my original method, at least with typical roller valve gear.
Im sure someone will prove me wrong on that last comment but there it is and I
stand by it for now.
Not sure how much this matters for the typical street driven Tiger but anal
retentive engineering types want to know!
Frank
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