Abstract: An exhaust valve includes: a shaft section; and a head section that is formed in one end of the shaft section and formed with a valve face that seats on a valve seat disposed in a cylinder head of an internal combustion engine, in which the shaft section has a shaft diameter of a constant diameter; the head section has a head diameter that is larger than the shaft diameter; and a thick shaft section that has a diameter smaller than the head diameter and larger than the shaft diameter is formed within a section between a connecting position that connects the shaft section with the head section and a position that is spaced apart from the head front surface opposite to the valve face in an axial direction by a distance that is approximately the same as the head diameter.

Abstract: A gasket provided in a gasket groove, receives the force that acts in the direction in which two pressure-adjusting oil passages are aligned in line, and the magnitude and direction of this force change as the difference between the hydraulic pressures in the pressure-adjusting oil passages varies. However, because the opening of a hydraulic oil supply passage is located on an imaginary line extending through between the openings of the two pressure-adjusting oil passages, pressure is applied from the hydraulic oil supply passage to the gasket, whereby constant and large frictional force occurs between the gasket and the side wall of the gasket groove. Thus, the gasket is firmly retained in the gasket groove, whereby the vibration of the gasket is suppressed.

Abstract: A cam cap has a wall portion that extends between two cam cap portions integrally formed and having connection portions respectively, and therefore the rigidity of the cam cap is high and thus the relative positional accuracies of oil passage connection faces of the connection portions are high even after the cam cap is mounted on an internal combustion engine.

Abstract: A cylinder head has a cylinder head body, a camshaft housing mounted on the cylinder head body, and cam caps mounted on the camshaft housing. The camshaft housing has through holes into which bolts are inserted to secure the camshaft housing and the cam caps together to the cylinder head body when assembling the engine. Internal threads are formed on the inner surfaces of the through hole, respectively. When rounding the cam holes before assembling the engine, second bolts are temporarily tightened to the internal threads of the through holes to secure the cam caps to the cam housing.

Abstract: A gasket provided in a gasket groove, receives the force that acts in the direction in which two pressure-adjusting oil passages are aligned in line, and the magnitude and direction of this force change as the difference between the hydraulic pressures in the pressure-adjusting oil passages varies. However, because the opening of a hydraulic oil supply passage is located on an imaginary line extending through between the openings of the two pressure-adjusting oil passages, pressure is applied from the hydraulic oil supply passage to the gasket, whereby constant and large frictional force occurs between the gasket and the side wall of the gasket groove. Thus, the gasket is firmly retained in the gasket groove, whereby the vibration of the gasket is suppressed.

Abstract: A cylinder head has a cylinder head body, a camshaft housing mounted on the cylinder head body, and cam caps mounted on the camshaft housing. The camshaft housing has through holes into which bolts are inserted to secure the camshaft housing and the cam caps together to the cylinder head body when assembling the engine. Internal threads are formed on the inner surfaces of the through hole, respectively. When rounding the cam holes before assembling the engine, second bolts are temporarily tightened to the internal threads of the through holes to secure the cam caps to the cam housing.

Abstract: A cam cap has a wall portion that extends between two cam cap portions integrally formed and having connection portions respectively, and therefore the rigidity of the cam cap is high and thus the relative positional accuracies of oil passage connection faces of the connection portions are high even after the cam cap is mounted on an internal combustion engine.