Four stroke internal combustion engine

Abstract

Engines having cylinders of noncircular cross section wherein the cylindrical curve is generated at a preselected constant outwardly normal distance from a closed curve. The closed curve is defined as including two spaced points on a major axis of symmetry of the cylinder with two continuously curved portions extending between these points and curved outwardly from the major axis. The closed curve about which the cylinder curve is generated is preferred such that there is a continuous change of curvature without discontinuity in that curvature in the cylindrical curve. The avoidance of discontinuity in the generating curve aids in mass production consideration and cutter life. A plurality of intake and exhaust port arrangements are disclosed illustrating four intake ports and four exhaust ports on opposite sides of the major axis of symmetry of the defined cylinder. In one embodiment, the outermost of the ports are smaller and are positioned closer to the major axis of symmetry. In another, the valves are oriented such that the stems thereof point to the centerline of the associated camshaft for direct actuation.