Why aren't valves polished?

[Theron Ross <ross@sanoh.com.mx>]

What is the reason why the entire valve isn't polished? What I'm talking
about is the base of the stem.

It seems weird that valves would be manufactured with a non-polished surface
that makes it easier for carbon deposits to form. Is the "rough" surface at
the base of the valve supposed to help with turbulence? That doesn't make
sense for exhaust valves since there is no need to create turbulence as the
exhaust leaves the combustion chamber.

What would be the result of polishing the base of intake and exhaust valves?
Is that even possible, or are they hardened?

The reason I'm asking is that I'm working on cleaning up my intake valves
and the carbon is a real bitch to get off. I would think that there would be
little, if any, carbon build up if the base of the valve was polished like
the stem. The Bentley says to use a wire brush wheel to get the carbon off,
but that seems a little too abrasive. As for the exhaust valves, they have
about 50K miles on them, so I got some new ones from Potterman.

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