[Top] [All Lists]

RE: 30 degree valve seats and 3 angle valve grid

To: "'Don Malling'" <>,
Subject: RE: 30 degree valve seats and 3 angle valve grid
From: "Dodd, Kelvin" <>
Date: Wed, 4 Dec 2002 08:34:47 -0800

You have the idea of a 3 angle grind.  Rather than using one cutting stone,
a sequence of cuts are made that give better flow characteristics.

Is this good?  As any performance modification, it depends on what you want.

It is more expensive to do, as three cuts are required.  Also from what I
understand, the sealing surfaces will erode at a higher rate than with a
traditional single cut.

So, it's like the old adage.  You can't get something for nothing.  You can
get higher flow, but you are going to be spending more money for a shorter
lived option.

Spending extra money on the valve grind wouldn't be my first step towards
improved efficiency and performance.  I think I would spend some time port
matching the intake and exhaust, which is a DIY cheap way to begin to get
better overall flow.  I've never done it, since I'm a lazy, un-organised
mechanic, but dowel pinning the manifolds and matching the ports seems like
a good starting point if you are serious about flow.

hope this is helpful


> -----Original Message-----
> From: Don Malling []
> Sent: Tuesday, December 03, 2002 10:09 PM
> To: 6-Pack;
> Subject: 30 degree valve seats and 3 angle valve grid
> David Vizard and others on these lists recommend 30 degree valve seats
> rather than 45 degree valve seats because they improve flow 
> at low valve
> lift. Rimflow and/or back cutting the valves also help during 
> low lift. 
> On page 207 of David Vizards "Tuning the A series Engine", he 
> points out
> that a single angle 30 degree valve seat reduces the port diameter as
> compared to that of a single angle 45 degree seat. So while the single
> angle 30 degree valve seat increases flow at low lift, the resulting
> narrower port reduces flow at high lift. He then points out that a 15
> degree sharp angle has the same flow characteristics as a 
> smooth radius
> bend. He then adds multiple 15 degree angles to the 30 degree 
> valve seat
> such that the port diameter approximates that of a single angle 45
> degree valve seat.
> Is this what a "3 angle valve grind" is, or is it something else??? 
> Thanks,
> Don Malling

///  or try
///  Archives at

<Prev in Thread] Current Thread [Next in Thread>