[200q20v] RE: Cam Discussion

[Calvin & Diana Craig]

Great discussion on the camshafts here guys, it sounds more like something
that I am used to seeing on my classical pontiac board I visit.  As far as
the different acceleration, deceleration rates, obviously the closer you get
to a step function (ignoring details like overlap, etc. which probably turns
the ideal shape into a trapezoid instead of a square) the more ideal it is.
A couple of reasons that cam duration is measured at 1 mm lift ( in the
musclecar world it's .050")  The first is to give a standard of comparison
so that cams can't "appear" to have a longer duration without really having
it.  The second is that significant airflow doesn't start to occur until
about this range of valve lift.  One comment from personal experience is
that Competition Cams started manufacturing cams a few years ago called
Xtreme Energy cams that were basically an ultra fast ramp rate cam.  The
camshaft wears out a little quicker than normal cams but holy cow does it
make a difference!  The difference is probably about 5-7% extra power (at
400 HP that's alot) over a similarly sized aftermarket cam that has what I
would term "normal" rates of open and close.  One of the reasons that
"roller valvetrains" are such a sought after commodity in the pushrod V-8
world is not because of the friction loss you lose but because they allow a
more aggressive (faster rates)cam profile to be run producing more power.
Just my 2 cents.
--Calvin