Don:
I *am* recommending the 30 degree back cut, the 3 angle valve
job, a pocket port, and the necked down, polished valves.
They all work. The only caveat is that each change by itself is
very small, but added together they give real power. These are the
small details that add up to real gains. The really nice thing about
these is that they do not affect emissions or mileage, and they are
increasingly used by the OEMs.
My 1995 small block Chevy, for example had the 30 degree back cut on
the valves from the factory. So GM believes in it too....
Vance
------------------------------
1974 Mimosa Yellow Triumph TR6
Cogito Ergo Zoom
(I think, therefore I go fast)
-----Original Message-----
From: Don Malling [mailto:dmallin@attglobal.net]
Sent: Monday, December 09, 2002 7:25 PM
To: Timothy Holbrook
Cc: 6pack@autox.team.net
Subject: Re: Fwd: Re: Fwd: RE: 30 degree valve seats and 3 angle valve
grid
Hi Tim,
Yes I ordered that back issue from Grassroots (Vizard) on a tip from Kai
and Robert Lang -- I think. But I don't think it's the same idea. I
thought the 30 degree angle they were talking about was on on the "face"
on the valve -- the piston side, rather than the valve seat. Seems they
were rounding the edge "face" to improve flow. The Vizard "A" series
manual is talking about the valve seat angle. The fact that he doesn't
mention the 30 degree valve angle in the DIY head porting article maybe
means it's not all that important -- but I thought Vance recommended
it... Maybe not, or maybe not strongly...
>From Vance...
However, when you add a 3 angle valve job to a 30 degree
back cut on the valve, necked down stems, polished valve faces,
and a mild pocket port, you can achieve improvements on the order
of 10% more HP, with no impact on emissions or drivability.
FWIW, Kas's manual shows the same sort of rounding on the valve face as
does the Grassroots article.
Don
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