Abstract: An internal combustion engine having a carburetor equipped with the usual throttle valve means controlling the flow of air-fuel flow to the intake manifold is provided with a normally open cut-off valve means located between the throttle valve and intake manifold to close communication therebetween when it is moved to closed position. A vehicle speed responsive device is operatively connected to the cut-off valve to move it to the closed position whenever the vehicle is coasting or moving under closed throttle valve conditions at or below a predetermined vehicle speed. In addition, there is provided a conduit between the intake manifold and the crank case with a pivoted plate clapper type check valve therein to permit flow from the crank case into the intake manifold.

Abstract: A pressure balancing system for an internal combustion engine wherein a conduit means connects the intake manifold to the crankcase for balancing the pressures therein. A valve is located in the conduit means and is responsive to the speed of the vehicle. A vehicle speed responsive device controls the opening and closing of the valve. The valve is normally closed at low or no speed and is opened at a predetermined speed, such as about 20 to 25 miles per hour, to connect the intake manifold to the crankcase so as to substantially balance the pressures therein at higher speeds. An oil separator may be inserted in the conduit means.