Abstract: A high velocity carburetor comprises a housing defining an air flow conduit with an air valve member therein. The air valve member includes a curved air-conducting surface facing the air stream and at least one position of the member for establishing a vortex flow. Fuel is supplied through the axial center of rotation of the air valve member to the conduit and into the vortex stream for facilitating atomization of the fuel into the air stream. The valve member is J-shaped or cylindrical. A fuel metering device is provided through the axial center of rotation of the air valve member which includes an axially movable but rotationally fixed inner fuel conduit mated to a rotationally movable but axially fixed outer tube. A cam is provided on the outer tube with a cam follower on the other tube to establish a needle fuel valve or metering fuel to the air conduit. This carburetor can be used in either a power-increasing or a fuel-efficient mode.