On Sun, 07 Sep 2003 12:57:16 -0700, terra wrote:

Roger Halstead wrote:
...
How about the cross sectional area through the intake and exhaust
ports to the valve seats? Are they matched, smooth, and optimized for
flow?

Smoothing the intake and exhaust ports is somewhat controversial. Some say

I don't know much about this, and it looks like John's answer was pretty good. I
have only one thing to add. I read somewhere, probably in a dirt bike magazine
long ago, that intakes should _not_ be highly polished. A slight texture helps
to keep fuel droplets suspended in the air, and not deposited on the walls of
the intake tract. Maybe little bumps in there are like vortex generators,
keeping the flow energized.

I used to sail a good bit, and got into the techy side of it,
measurement, handicapping, etc. It was well recognized that a super
slick hull finish was NOT good for the reasons mentioned, flow
separation. A very smooth in-line sanded finish was thought to be
best.

Maintainence of attached flow is ultra important. I would THINK that
bead blasting of intakes would offer the best finsih.

George