Martin - many older carburetors (including the Carter type BB-1) have a fuel valve external to the carburetor. The valve seat screws into the carb from the outside, and the fuel line screws directly into the fuel valve seat. Virtually all single barrel Strombergs in the 1930's including the so-called Stromberg 97 (actually an EE-1) are so-equipped.
It minimizes volume inside the carburetor required for the float arm.
Jon.
