Perihelion Design has a 3” slicer valve that would probably work.

 http://www.periheliondesign.com/moreproducts.htm

Bill b

I'm looking for a source for an air valve which can be opened or closed under ram air pressure and will withstand cabin pressurization when closed.

Let me first explain my application:

When I got the airplane, the previous owner had closed off the fresh air inlet on the vstab.  So instead I ran some scat tubing from the cowl inlet to a valve on the firewall.   The valve I have is a home brew device which is not working out very well.   Mainly it has trouble overcoming ram pressure when I need to close it.

Can anyone point me at a device or source for a device that might work in this application?

thanks,

Colyn