Re: 10V heads

[steveb@newkla.kla.com (Steven Buchholz)]

Dan:

I've heard very good things about extrude honing.  As the slurry flows 
through the runners it is affected by the geometries of the intake in 
much the same way that the air would, grinding away impediments to flow.  
I don't know how much risk there is of breaching the walls of the manifold.  
I've been considering this for the next time I have to rip the manifold 
out of the Coupe (which may be soon as you know!)  It would be nice to 
hear from someone with experience!

WRT valve sizing ... what kind of lift do you have on the cam?  Turbo-
motors have positive pressure at both ends, so I would probably lean 
toward increasing the inlet and exhaust areas by comparable amounts.  
I don't speak from much experience here though.

WRT partial porting of the intake runners ... on a non-turbo motor you 
would definitely lose some of the ram-air effect for which the runners 
are intended by only widening the tail end of the runner.  I understand 
that there are some who have had the intake manifold cut open to allow 
the entire runner to be ported!  I wonder how much difference there is 
since you have a pump forcing air down the runners.  It is probably true 
that the fact that the runner has a smaller diameter at one point restricts 
the amount of air fed down the runner, limiting the effectiveness of the 
porting job.  

Good luck with the new head Dan!  Thanks for the info and keep us up to 
date on the final decisions and results!

There were a couple of other processes I was interested in.  The engine 
compartment of the TQC gets pretty hot ... I remember looking under the 
hood after a long nighttime freeway trip and seeing a dull red glow coming 
from the turbo. I was wondering if the "Jet Hot" ceramic coating process 
for the exhaust manifold (& turbo?) was worthwhile?  There is a place in 
the midwest called the Metric Mechanic that tunes BMW motors.  They have 
a porting process that guarantees turbulent flow at the boundary layer of 
the manifold & head.  This could make the head/manifold flow better, 
because the turbulence breaks up the tendency for the air to flow along 
the walls of the manifold.  This is actually one of the things that 
extrude honing could adversely affect.  Extrude honing produces a surface 
that is very smooth and will promote laminar flow near the walls.  Does 
anybody out there have any experience with turbulent flow porting?

I LOVE THIS NEWSGROUP!
Steve Buchholz
s_buchho@kla.com