Internal combustion engine

An internal combustion engine comprising:

• a cylinder block in which a plurality of cylinders are formed;
• and a cylinder head that forms a plurality of combustion chambers in conjunction with the cylinder block,
• wherein the cylinder block and the cylinder head are formed into one body,
• the cylinder head includes:
• a plurality of intake passages each of which communicates an intake pipe with one of the plurality of combustion chambers;
• a plurality of exhaust passages each of which communicates an exhaust pipe with one of the plurality of combustion chambers;
• an intake-side cam journal that supports, in a rotatable manner, an intake-side cam shaft that displaces intake valves that open and close the intake passages;
• and an exhaust-side cam journal that supports, in a rotatable manner, an exhaust-side cam shaft that displaces exhaust valves that open and close the exhaust passages,
• an upper surface of the cylinder head is divided, along a direction in which the plurality of cylinders are arranged, into first regions that are regions that overlap the combustion chambers as viewed from an axial direction of the cylinders and a second region that is a region located between two of the first regions adjacent to each other,
• at least either the intake-side cam journal or the exhaust-side cam journal is disposed in the second region, and
• an opening area of an exhaust valve hole that is an opening of the exhaust passage opening to the combustion chamber is set to be larger than an opening area of an intake valve hole that is an opening of the intake passage opening to the combustion chamber.