ENGINE BASICS

On Jun 9, 8:35*pm, "Tom Wait"
wrote:

I'm going to go out on a limb here Bob and say that the RATE of valve
opening and closing is a function of RPM and cam lobe contour only. Mass of
the valve train would primarily affect the max RPM attainable without
destructive valve float.
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Dear Tom,

Not a problem. There's plenty of room on the limb for the two of us.
(See my error as caught by Charlie.)

With regard to the rate at which the valve opens, what I'm trying to
say is that a valve train having greater mass will open more slowly
than a valve train having less mass. The assumption here is that all
else -- including the factor you've mentioned -- are equal.

The object here was ways to increase Volumetric Efficiency, for which
the rate at which the cylinder fills is a critical factor. According
to Taylor (or possibly Litton) the shape of the combustion chamber,
especially with regard to the shrouding of the intake valve, AND the
mass of the valve train components, are the only ways of improving VE
without going to super-charging.

I can see where you're coming from with regard to RPM but as you must
know, VE falls as rpm increases. The idea behind lighter valve train
components is to allow more time for charging the cylinder at a given
RPM. For the purpose of this exercise, RPM is fixed.

So put away the saw -- there's plenty of room for the two of us on
this branch :-)

In a more serious vein, I apologize for stating my explanation so
poorly.

-R.S.Hoover