In terms of fluid dynamics, the volumetric and combustion efficiency of an engine are dependent on the fluid dynamics in the engine manifolds and cylinders. The changing characteristics of the air flow jet that tumbles into the cylinder with swirl via intake valves and the exhaust jet through the exhaust valves as they open and close can be determined, along with the turbulence production from swirl and tumble due to compression and squish. Model simulates the aerodynamics of the air induction and end compression stages for a canted valves IC engine. Processing in ANSYS Fluent, one of the first conclusions will be that the valve diameter is a fine tradeoff between the need for a bigger diameter involving a grater mass of air filling the cylinder, and the need of a smaller diameter in order to reduce the blind zone. The relative pressure indicates a suction effect coming from the moving piston. The more the shape of the inlet port is smoother and the diameter of the piston is bigger, the aerodynamic resistance of the geometry will be smaller so that the difference of inlet port pressure and the pressure near to piston face will be smaller. The analysis will target the Mitsubishi Marine Engines, S6U designed for Tug Boats.