Cylinder head for an internal combustion engine having: - a body with an upper face, a lower face, two end faces (5,6) and two lateral faces (10, 13), - said body integrating in a single cast piece, the engine exhaust manifold (16, 17), - said exhaust manifold (16, 17) being defined by a plurality of conduits for the exhaust gases provided in the body of the head and forming separate subgroups (16, 17) of exhaust conduits merging into manifold portions (16a, 17a) superimposed and spaced apart from each other which terminate on a lateral face (13, 14) of the head, - a lower cooling jacket and an upper cooling jacket provided in the body of the head, substantially below and above conduits defining the exhaust manifold (16, 17), and an intermediate cooling jacket interposed between the abovementioned manifold portions (16, 17) which are superimposed and spaced apart from each other, - said intermediate jacket communicating with the lower and upper jackets (18, 19) through two interconnection conduits arranged adjacent to said lateral face (13, 14), at the two sides of the outlet area of the exhaust manifold. wherein: - the lower cooling jacket is longitudinally divided into a plurality of separate transverse chambers associated to various engine cylinders, and terminating in a longitudinal continuous portion of said lower jacket, extended along the exhaust side of the head, - the intermediate cooling jacket is extended over the entire longitudinal extension of the head, it has conduits for communication with the abovementioned chambers of the lower jacket and an outlet at one end of the head, for the exit of the cooling fluid from the head, - the upper cooling jacket has a first portion at the centre of the head, above the upper portion of the exhaust manifold, and a second portion extended longitudinally from said first portion up to said end of the head, where it forms an auxiliary circuit adjacent to said main outlet, said cylinder head being characterized in that: - said conduits of the exhaust manifold merge into a common outlet terminating on said lateral face (13, 14) of the head, - said plurality of separate transverse chambers of the lower cooling jacket which are associated to the various engine cylinders are defined by partitions transverse to the longitudinal direction of the cylinder head which are provided in a single piece with the cylinder head, said transverse chambers being adapted to receive cooling fluid from a circuit provided in the engine block by means of conduits which respectively supply cooling liquid coming from the circuit provided in the engine block to said separate transverse chambers, - said second portion of the upper cooling jacket forms an auxiliary outlet adjacent to said main outlet at said end of the head. - a body with an upper face, a lower face, two end faces (5,6) and two lateral faces (10, 13), - said body integrating in a single cast piece, the engine exhaust manifold (16, 17), - said exhaust manifold (16, 17) being defined by a plurality of conduits for the exhaust gases provided in the body of the head and forming separate subgroups (16, 17) of exhaust conduits merging into manifold portions (16a, 17a) superimposed and spaced apart from each other which terminate on a lateral face (13, 14) of the head, - a lower cooling jacket and an upper cooling jacket provided in the body of the head, substantially below and above conduits defining the exhaust manifold (16, 17), and an intermediate cooling jacket interposed between the abovementioned manifold portions (16, 17) which are superimposed and spaced apart from each other, - said intermediate jacket communicating with the lower and upper jackets (18, 19) through two interconnection conduits arranged adjacent to said lateral face (13, 14), at the two sides of the outlet area of the exhaust manifold. - the lower cooling jacket is longitudinally divided into a plurality of separate transverse chambers associated to various engine cylinders, and terminating in a longitudinal continuous portion of said lower jacket, extended along the exhaust side of the head, - the intermediate cooling jacket is extended over the entire longitudinal extension of the head, it has conduits for communication with the abovementioned chambers of the lower jacket and an outlet at one end of the head, for the exit of the cooling fluid from the head, - the upper cooling jacket has a first portion at the centre of the head, above the upper portion of the exhaust manifold, and a second portion extended longitudinally from said first portion up to said end of the head, where it forms an auxiliary circuit adjacent to said main outlet, - said conduits of the exhaust manifold merge into a common outlet terminating on said lateral face (13, 14) of the head, - said plurality of separate transverse chambers of the lower cooling jacket which are associated to the various engine cylinders are defined by partitions transverse to the longitudinal direction of the cylinder head which are provided in a single piece with the cylinder head, said transverse chambers being adapted to receive cooling fluid from a circuit provided in the engine block by means of conduits which respectively supply cooling liquid coming from the circuit provided in the engine block to said separate transverse chambers, - said second portion of the upper cooling jacket forms an auxiliary outlet adjacent to said main outlet at said end of the head.