SU carburetor

From WOI Encyclopedia Italia

SU carburetors (named for Skinners Union, the company which produced them) were a brand of sidedraft carburetor widely used in British and Swedish (Volvo, Saab 99) automobiles for much of the twentieth century. Originally designed by George Skinner in 1910, they remained in production through to the 1980s. Hitachi also built carburators based on the SU design, they were used on the 240Z among other Datsun Cars, while they look the same, there are different enough that needles are the only part that fits both.

SU carburetors featured a variable venturi controlled by a piston. This piston has a tapered, conical metering rod that opens and closes the passage of fuel, so the movement of the piston is converted into getting the correct proportion of fuel.

The piston is moved up and down by the partial vacuum in the inlet manifold, depending on the position of the throttle plate, between the carburetor piston and the manifold.