Headwork on a cracked head?

[Michael Pederson]

Jorgen -

I believe the 10 valve 5 cylinder head on the Audi is very similar to the VW
8 valve 4 cylinder head; that's certainly the case for the Audi 20 valve 5
cylinder design.  I have a VW GTi 16 valve head sitting in my garage next to
a new AAN 20 valve head - the ports & valve layouts are basically identical
right down to the "bump" in the floor of the intake port runners.  If this
holds true for your head design, you can apply a lot of the VW tuning
expertise (& parts) directly to your Audi project.  A search of the web will
give you a number of sites that claim to have practically "off the shelf"
big valve VW set ups for the VW's 2 valves per cylinder.

The 4 valve per cylinder (Audi 20 valve/VW GTi 16 valve) however are
another, more complicated  story.  The valves can be enlarged, but its a lot
more work and there are, I'm told, a number of parameters that need to be
kept in balance (i.e. ratio of exhaust valve curtain area to intake curtain
areas etc.) A good general reference starting point might be to locate a
copy of Greg Raven's "Water Cooled Volkswagen Performance Handbook," MBI
Publishing 1999.  He's got a whole chapter on two, four & five valve heads
and the cross applicability thereof that should be analogous to the Audi 5
cylinder world.

Mike P.

-----Original Message-----
From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com]On
Behalf Of Jörgen Karlsson
Sent: Wednesday, December 06, 2000 8:18 AM
To: quattro at audifans.com
Subject: Headwork on a cracked head?


Hi,

I have looked at porting the head that is going into the 80TQ -83, the
problem is that the head I have here is cracked between the valves. I know
that it should be ignored as long as it is not leaking, but I don't want to
spend the money for a pro port job on a cracked head.

I have heard the term siamesed valveseats here on the list when discussing
larger valves. I guess that it means that the intake and exhaust valve seat
is made from one pice of metall. Has anyone done this? As I see it this will
fix the crack in my head as well.

The above leads me to the valves, where do I get bigger valves, the intake
valve is probably not a problem but where do I get a bigger sodium filled
exhaust valve? What sizes are suitable?


Jörgen Karlsson