Fuel intake system for multi-cylinder internal combustion engine

In a fuel intake system for a multi-cylinder internal combustion engine having at least first and second sets of engine cylinders, and having at least first and second primary intake passage means respectively in communication with the engine cylinders of the first and second sets, a carburetor means for combining fuel with air to form a primary combustible mixture to be supplied to the engine cylinders of the first and second sets through the respective first and second primary intake passage means, a plurality of throttle valves equal in number to the number of the primary intake passage means and operatively positioned respectively within the first and second primary intake passage means for controlling the rate of delivery of the primary combustible mixture to the engine cylinders of the first and second sets, and an idle and low-speed fuel circuit for providing an auxiliary combustible air-fuel mixture for enabling the engine to be operated at an idling speed, the improvement which comprises a first connecting passage means extending between said first and second primary intake passage means at a position downstream of the throttle valves with respect to the direction of flow of the primary combustible mixture towards the engine cylinders of the first and second sets, a second connecting passage means extending between the first and second primary intake passage means at a position downstream of said first connecting passage means for establishing a free fluid communication between said first and second primary intake passage means, and a mixing chamber in said first connecting passage means and having a substantial volume and in communication with said idle and low-speed fuel circuit, said idle and low-speed fuel circuit including an air by-pass passage having one end in communication with a source of air and the other end connected to said mixing chamber, a portion of the bottom of said mixing chamber being aligned with the opening of said other end of said by-pass passage and having a curved guide for deflecting the flow of the auxiliary combustible mixture generally at right angles towards a portion of a peripheral wall of said mixing chamber opposite to said curve guide.