Re: Head Porting

["Graydon D. Stuckey" <graydon@apollo.kettering.edu>]

On Sat, 31 Jul 1999, Todd Phenneger wrote:

> All the way through what.  It fully bridges between the two valves but it
> appears that piece of material is pressed in there or something and isn't
> part of the casting.  The casgint below seems fine.  

The valve seats are pressed in.  They should not be cracked.  However, 
the aluminum between the valve seats is permitted to be cracked by the 
factory, and the crack is allowed to be up to a mm wide if I remember my 
Bentley.

> Hey, do I need NEW valves if I want to get a valve job or can they grind
> the old ones???

You should be able to use your old valves.  When I did my 5KCSTQ head, 
the valves were like brand new at 200,000 miles.  I found a taper in the 
valve stem tha twas about 0.0005" (smaller near the head) which threw off 
my machine shop.  I should have taken that as a clue.  I found out from 
an engine builder whom I do trust, that Audi made the valves like that 
from the factory to allow for thermal expansion being greater near the 
head than the tip of the stem.  If you see the same taper, you can 
probably reuse your old valves.

BTW, I used a head from a normally aspirated 5000 and there were no 
cracks at all.  Probably because it hadn't seen anywhere near the thermal 
stress tha tmy turbo head had seen.

Later,
Graydon D. Stuckey
'91 V8 Quattro 5-speed		'86 Mazda RX7 TII+2
I have a new exhaust systems webpage - check it out at...
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