An internal combustion engine of the two- or four-stroke petrol, diesel or gas-fueled type, comprising: an engine block which forms internally at least one cylinder; a head which contains a cylindrical rotary distributor which is adapted to connect, by means of two internal ports, a combustion chamber of the at least one cylinder alternately to the air intake and to the gas exhaust; a plate for closing the head in an upper region, in which intake and exhaust conveyance channels of the engine are provided; for each at least one cylinder being provided a single sealing element which is arranged between the at least one cylinder and the rotary distributor. The sealing element has a cradle which is shaped complementarily with respect to the rotary distributor and a cylindrical protrusion that has an open cavity which forms the combustion chamber of the cylinder. The sealing element has a port for connection between the combustion chamber and the two internal ports of the rotary distributor which is formed through the cradle. The upper closure plate of the head has a portion, which is inserted between the walls of the head, which faces and is substantially shaped complementarily with respect to the rotary distributor.