from the major diameter edge of the opening other angles may be used in place of a 7 degree angle without departing from the spirit and scope of the present invention the mentioned angle of inward taper is just an exemplary angle for producing a desired venturi effect for air entering a carburetion system enhanced with valve 103 an axis 306 defines the substantial centerline of opening 302 it is noted herein that with respect to an intake port of a carburetion system valve 103 is uniquely caused to rotate such that opening 302 no longer communicates air into the carburetion system and surface 301 functions as a sealing agent over the intake port more detail about operation of valve 103 is provided further below the overall major diameter of valve 103 may vary widely without departing from the spirit and scope of the present invention in a preferred embodiment the size of valve 103 will depend at least in part on the size of a port on a carburetion system that will be enhanced by the valve in accordance with the present invention similarly the dimensions of opening 302 may also vary accordingly fig1 c is an elevation view of a carburetion system enhanced with anti back streaming valve 103 of fig1 a and fig1 b cause to assume a vertical position during active air intake according to an embodiment of the present invention the carburetion system illustrated herein includes a fuel carburetion device or carburetor 101 carburetor 101 may be any type of carburetion device such as are known in the art including single barrel two barrel or four barrel type devices carburetor 101 may exhibit many different physical features forms and shapes without departing from the spirit and.