RE: 10V heads

[Dave Lawson <dlawson@ball.com>]

Hi Dan,

>1) The original (now deceased) ABT head had the stock 33mm exhaust valves,
>but the intake valves were increased from 38mm to 40mm.  The guy at the
>head shop claims I'll get better performance if I instead open up the
>exhaust.  So, since I have 2mm of extra valve size to play with, do
>I put it all on the exhaust side, split the difference and go 1mm up
>in size on both the intake and exhaust, or stick to what I had before
>and increase only the intake by 2mm?

I was thinking along the same lines and also heard this idea from Ned 
Ritchey a while back. We were talking about head updates and I asked him 
what he thought. He said that he would go with an increase in exhaust valve 
size, because the turbo is  helping to cram in air into the cylinder so the 
intake side doesn't need help, but the exhaust track seems to be limited by 
the valve size and an increase here will help engine breathing. As you have 
probably thought about, do you think Abt really knew why they installed a 
40mm intake valve, other than it was another upgrade they could sell and 
make money with?

Some info from the book  "quattro development and competition history by 
Jeremy Walton" show that the factory rally cars increased the valve size on 
both the intake and exhaust valves in the 1981 Group 4 quattro coupe. They 
increased the inlet valve from 38.2mm to 41.1mm and the exhaust valve from 
33.3mm to 35.2mm. And this was with a 79.5mm bore and 86.4mm stroke engine. 
These increased valve sizes were also used both the A-1 and A-2 Group B 
competition quattro coupes.

>2) The old head had it's intake ports widened a significant amount,
>and the openings in the intake manifold were widened to match.  The
>problem here is that because of the shape of the intake manifold, it
>was only widened as far into the intake runners as the die grinder
>could reach.  The guy at the head shop says this is bad, because as
>the air comes through the throttle body and enters the runners, it's
>gonna expand as it goes from the narrow region to the wider region,
>thus reducing the air velocity before it enters the head.  He claims
>I either need to widen the intake manifold runners along their entire
>length (extrude honning, perhaps?), or get a stock intake manifold
>and not bother widening the passages on either it or the head.  What
>do y'all think?  Anyone out there have any experiences with extrude
>honning?

I think you are correct in not wanting an inlet tract which gets wider and 
then narrower as this will effect the air velocity. But then, what do I 
know. For extrude hone experience, give Kent Anderson a call(612.937.8639), 
he has recently finished an engine for an 83 TQC in which they had a bunch 
of stuff extrude honed, like the intake manifold, exhaust manifold, head, 
turbocharger, and I forget what else. His opinion is it really helps. When I 
checked into prices, it was something like >$1200 to get the intake 
manifold, exhaust manifold and head processed. Not cheap.

I am interested in hearing what your descision is. BTW, have you found a 
source for 35mm sodium filled exhaust valves? If so, where do you get these? 
or the 40mm intake valves for that matter?
 -
Dave Lawson  dlawson@ball.com