This item is a boost activated, adjustable power valve used in blow through supercharger and turbo carbureted applications in 4150 and Dominator carburetors.
These valves are machined and assembled in our shop and set and tested on fixture.. Made of 100% USA materials. 
Machined from solid billet extrusion. Stainless steel check ball, stainless spring and brass seat for corrosion free long life operation no matter the fuel used. O ring seal , No gasket needed.
Boost referenced by bowl pressurization..The more boost there is, the farther they open to compensate for fuel demand ramp. These are an "open to the fuel bowl" full flow design with no restriction to flow or delay to boost pressure like another design out there. No diaphragm to rupture or ever wear out. 
Valve can be used in the primary or secondary side. secondary side will require 3/8 OD pick up tube affixed to brass ext tube.. If you need a secondary ext.. contact us and let us know what fuel bowls you have and we will include an extension to the shape you will need.
We have 1000's in service to Date and  quite a few helping to power 3 and 4 second 1/8 mile cars.
Visit our Face book Page at scs performance induction and give us a like. tech help and advice can also be had there. 
 We brought this unit to market 9 years ago to help make BT carbs a viable option for the DYI's out there.. This is the original and Not the Copy cat that is out there. BEWARE THE yellow CHINA RIP OFF. They even stole my listing word for word in one of their adds from some seller in Kentucky.
instruction sheet included. Note: THESE ARE NOT INTENDED FOR and WILL NOT WORK IN Draw through applications, such as roots blower.. Blow through means boost is " blown" through the carburetor.
any and all questions welcome and encouraged. Please ask questions..
Thanks for looking.