Cylinder head

A cylinder head comprising:

• a cylinder head body including a water jacket through which a coolant circulates,
• the water jacket being provided inside the cylinder head body,
• the cylinder head body having a plug hole penetrating through the cylinder head body, the plug hole being provided for each of a plurality of cylinders of an internal combustion engine such that an ignition plug is passed through the plug hole,
• the cylinder head body further having two intake ports and two exhaust ports per plug hole, the two intake ports and the two exhaust ports being provided inside the cylinder head body such that the two intake ports are placed on a first side of the cylinder head body in a short direction of the cylinder head body with respect to the plug hole and the two exhaust ports are placed on a second side of the cylinder head body in the short direction of the cylinder head body with respect to the plug hole,
• the water jacket including:
• an intake-port-to-intake-port passage portion communicating with an outside of the cylinder head and extending between the two intake ports;
• an exhaust-port-to-exhaust-port passage portion communicating with the outside of the cylinder head and extending between the two exhaust ports;
• a central passage portion communicating with the intake-port-to-intake-port passage portion and the exhaust-port-to-exhaust-port passage portion, the central passage portion being formed so as to surround the plug hole;
• and
• a discharge passage portion communicating with the central passage portion and extending toward the outside of the cylinder head.