A cylinder head for an internal-combustion engine, comprising, for each cylinder of the engine: - at least one intake duct defined by a cavity extending through a body of the head starting from an inlet located at a lateral face of the head down to an outlet cylindrical mouth opening out on a bottom face of the head, - an intake valve associated with each intake duct and including a valve stem and a valve head cooperating with a valve seat defined at said outlet cylindrical mouth, said cylindrical mouth being coaxial with said valve stem, wherein the surface of said intake duct has a projection which is longitudinally elongated in a direction substantially parallel to the axis of the intake duct, for deflecting the flow of air that flows through the intake duct, thus creating a desired field of motion of the flow of air in the cylinder of the engine, wherein said air-deflecting projection is formed on the side of the surface of the intake duct that is closer to the bottom face of the cylinder head, wherein said air-deflecting projection has a plane of symmetry containing the axis of the valve stem and has a first end facing towards the inlet of the intake duct and a second end facing towards the outlet mouth of said intake duct, the cylinder head being characterized in that: - said air-deflecting projection is configured to provide a deflection of the air flow towards the two sides of the valve stem, so as to reduce the quantity of air that hits the valve stem directly, - said air-deflecting projection extends down to said outlet cylindrical mouth and is configured in such a way that said air-deflecting projection hinders a flow of air through an angular sector of the cross-sectional area of said outlet mouth which angular sector faces towards said lateral face of the cylinder head, - the ratio between the width of the cross-section of said air-deflecting projection and the diameter of the valve stem is between 0.8 and 1.2, so that the valve stem lies in the shadow of the air-deflecting projection with respect to the air flow through the intake duct, and - at said second end thereof the air-deflecting projection has a front face arranged substantially flush with, and along an extension of, a portion of the surface of the outlet cylindrical mouth. - at least one intake duct defined by a cavity extending through a body of the head starting from an inlet located at a lateral face of the head down to an outlet cylindrical mouth opening out on a bottom face of the head, - an intake valve associated with each intake duct and including a valve stem and a valve head cooperating with a valve seat defined at said outlet cylindrical mouth, said cylindrical mouth being coaxial with said valve stem, - said air-deflecting projection is configured to provide a deflection of the air flow towards the two sides of the valve stem, so as to reduce the quantity of air that hits the valve stem directly, - said air-deflecting projection extends down to said outlet cylindrical mouth and is configured in such a way that said air-deflecting projection hinders a flow of air through an angular sector of the cross-sectional area of said outlet mouth which angular sector faces towards said lateral face of the cylinder head, - the ratio between the width of the cross-section of said air-deflecting projection and the diameter of the valve stem is between 0.8 and 1.2, so that the valve stem lies in the shadow of the air-deflecting projection with respect to the air flow through the intake duct, and - at said second end thereof the air-deflecting projection has a front face arranged substantially flush with, and along an extension of, a portion of the surface of the outlet cylindrical mouth.