10v big valve conversion

[Eric Sanborn]

Alan Pritchard wrote:

>Also may consider ceramic coating the combustion area.
>So, what is a sensible cr (thinking 10.5-10.8 ish).
>And what valves are used for the big valve conversion? 
>thanks
>
>  
>
I would also be interested to see what valves would work.  US market 
Golf II 1.8l heads were hydraulic and had 40 mm intake valves.  I had 
planned to put that in my turbo project, but my local machine shop was 
not comfortable with doing the machining.  He felt it would require new 
larger valve seats and reshaping of the combustion chamber.

If your car has the fat stem base exhaust valves I would look into 
custom stainless valves instead to increase exhaust port flow.  Take a 
look at this picture http://sofadog.net/4ktq/images/ExValves.JPG.  The 
valve on the left is out of an '83 GTI with solid lifters.  The one on 
the left is out of a KH engine.  They are both the same diameter valve 
and have the same diameter stems up by the valve guide.  See the big 
difference at the base of the stem?  Yes I know in the case of a turbo 
engine one would be giving up sodium filled, but one would also be 
giving up wieght.

As for the coating I strongly recommend it.  My KH engine has pretty 
much everything you can do except for the intake manifold (ran out of 
time).  I am not really pushing the limits yet on this engine, but I 
have seen with other cars that coatings offer a strong level of 
protection against damage from detonation.  I have not done a before and 
after comparison, but it would make sense that it would also reduce the 
engine's cooling load as more heat is kept in the combustion charge.  If 
you are adventurous and have a blast cabinet and air brush do the 
coatings yourself and save a bundle.

If you do go with big valves be sure to post the method and parts you 
use.  I would be very interested to see how it goes.

-- 
Eric Sanborn
'85 4ktq

http://sofadog.net/4ktq/