Porting and polishing help

[JShadzi at aol.com]

As far as porting goes, a good site is www.standardabrasives.com, they have a 
writeup on general porting, and also sell some good kits to get you started.

The best thing to do if you don't have a flow bench is to do a basic polish 
and port match, go in a smooth all the ports to an 80 grit finish, match the 
IM and EM ports to the head.  The 40mm valve is a great upgrade in NA cars, I 
also have 40mm vavles in my 80tq, the motor breathes very well.  The Sodium 
valves are a great saftey mechanism to keep from burning exh. valves, and I 
have not found a good replacement as of yet, but I would really like to do a 
head with 41/36mm vavles (what the TransAm car had).

Also, on NA cars, you can have 1.5mm machined out of the ID of the valve seat 
which effectively gives you a bigger valve, but since it removes valve seat 
area, it is not recommended for a turbo motor where valve cooling is 
important.  

As a rule of thumb, you can attribute about 5-10% gain in the 4kRPM range and 
up to porting.

HTH,
Javad
www.80tq.com

In a message dated 7/28/2001 10:12:59 PM Pacific Daylight Time, 
Schwnnbkr1 at aol.com writes:

<< While were on this topic... I know it's not as important in a 
 turbocharged engine, but what type of gains can be seen when opening up the 
 heads on the 10v? Is a larger (conventional) exhaust valve worth sacrificing 
 the sodium-filled Audi valves?
  >>