[T3] valves

[Jim Adney]

On 25 May 2016 at 6:33, Mike Fisher wrote:

> I've heard of 3 angle grind of the valve seat that is supposed to flow a
> little more fuel for racing purposes.  I'd say it was mostly a 'marketing
> tool' for Machine Shops.

It's the VW standard, as described in the Bentley manual, as well as 
an industry standard. Grinding just the central angle is a shortcut 
that gives a wide central angle which tends to collect carbon.  

Doing the single angle used to be a cheap way to go, back when 
grinding was done with stones which had to be changed for each angle. 
But today, the cut is done with a carbide cutter that is already 
shaped to all 3 angles. It's slick and amazing, and it's what any 
machine shop will do if they have modern equipment.

The 4th angle, to the intake valve, is a high performance add-on. 
It's easy to do, but they have to be careful that they don't remove 
any material where the seat and valve meet. In other words, that 4th 
angle on the valve must fall completely INSIDE where the sealing 
surfaces mate.

-- 
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
*******************************