A valve of the type wherein a valve member having a passageway therethrough is rotatably mounted within a valve body or housing having inlet and outlet passages. The valve body is provided with one or more raised portions on its interior surface which serve to firmly engage or bias the valve member when it is rotated to the closed position, thereby preventing leakage between the valve member and the body. In the manufacture of such a valve in accordance with the method of the present invention, the valve body is formed of a suitable plastic material and is molded about the valve member. The valve member is placed in the open position in the mold and is provided with one or more recessed portions on the outer surface thereof so that complementary raised portions are formed on the inner surface of the molded valve body which serve to firmly engage or bias the valve member when it is rotated to the closed position.