3 Angle Valve Seats ...

["Freed, David (Exchange)" <dfreed@bear.com>]

	Date: Thu, 02 Sep 1999 11:47:27 GMT
> From: quk@isham-research.demon.co.uk (Phil Payne)
> Subject: Re: 3 angle valve seats...
> 
> In message <37CE32D0.E628D89@poboxes.com> Gerard writes:
> 
> > I'm off into a bit of a panic here to get my cylinder head
> > reconditioned on the 1990 200 with MC motor. I just got off the
> > phone with one of the biggest local performance shops and they
> > quoted me some R4400 ($730) for a complete recondition and
> > gas flow of the cylinder head. This includes parts (seals,
> > stems, no lifters), gas flowing and a 3-angle valve seat job.
> 
> In the UK, an exchange head would:
> 
> a) be cheaper
> 
> b) give you new lifters, guides, springs and cam in addition.
> 
> > Question: what is the effect of this 3-angle seat job?
> > Benefits on a turbo motor?
> 
> Audi requires it.  The valve seat is ground to three angles in the
> stock engine - a section at 30 degrees to the roof of the combustion
> chamber and a section at 45 degrees to the inside of the port, joined
> by a band 2mm wide for an inlet port and 2.4mm wide for an exhaust
> port.
> 
> 
> - --
>  Phil Payne
>  UK Audi quattro Owners Club
>  Phone: 0385 302803   Fax: 0870 0883933
> 
> ------------------------------
	Most good head rebuilders use a 3 angle valve job to bring a
reground valve seat (it gets wider as you grind it) back to stock width and
have the seat meet the valve in the correct spot on the valve's mating
surface.  It also helps smooth the flow of air as it passes the valve seat
(a little).  You are paying for the flowing of the head which should include
basic porting to match the air flows of each port, both intake and exhaust.
Porting is time consuming (esp. if it is well done) and costly.  If you have
someone who can flow it for you cheap that's great but in most cases you get
what you pay for.  Meet the guy doing the porting and flowing before he
begins and tip him well.   He will be more willing to take his time and give
you a good job.  Gasket match the ports as this is a critical area that
often creates turbulence in air flow.  This is more important than flowing
because the ports usually miss their alignment by a lot.  



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