An intake and exhaust system through rotatory port shafts, in four-stroke motors, through which are suppressed the camshaft, valve tappets, rocker arms and valves of conventional motors. The system is based on a hollow shaft (4) located in a jacket (5) and the whole assembly is mounted on the cylinder head body (1) of the engine and supported on bearings (6,7). The shaft has ports (12) transversely through in communication with the cylinder chambers (2), quite independently from the combustion order, having the ports shaft lubricating (18) and water-cooling (13,14) means, being engaged the shaft to a gear driven by the crankshaft (3) of the engine, being 1 : 4 the ratio of the shaft (4) to the crankshaft (3) rotation.