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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,289
Thanks, and yeah, it's just the first inch and a half or so you open up.
The rest of the bowl area and short side radius is just smoothing and blending the casting marks and crude factory machine work just below the valve seat.

You do not want to remove much material from the short side radius and some people add material there by welding in more aluminum and then regrinding the short side radius contour so the mixture is lifted up higher before it curves and goes over the short side radius. That way it has more room to straighten out before it hits the back of the intake valve. That reduces bad turbulance at the back side of the intake valve opening radius and increases flow CFM into the combustion chamber. Even more so in normally aspirated motors.

It's the opening up the first inch or so of 930 heads from 32mm to whatever you decide to go with that makes 95% of the difference. The rest of the bowl area and valve guide streamlining is already good from Porsche and smoothing and blending that area really doesn't make much difference, especially in a forced induction motor. Every little bit helps to some degree though even if it's only in your head.
Old 06-21-2013, 09:20 AM
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