Internal combustion engine

An internal combustion engine, comprising:

• a head cover;
• a cylinder head that is connected to the head cover;
• a valve guide that is cylindrical in shape and that is fixed to the cylinder head;
• a valve that is inserted into the valve guide;
• and
• a valve operating mechanism for operating the valve, wherein
• the head cover and the cylinder head define an accommodation space for accommodating the valve operating mechanism,
• the cylinder head includes a gas passage through which gas flows, and a fixing hole that leads from the accommodation space to the gas passage,
• the valve includes a shaft body that is inserted inside the valve guide, and a valve element that extends from the shaft body to open and to close the gas passage,
• a material of the valve guide is a porous material,
• the valve guide is inserted into the fixing hole, and also a portion of the valve guide protrudes from the fixing hole into the accommodation space,
• with a portion of the valve guide that is exposed to the accommodation space as an exposed portion and a portion that is inserted into the fixing hole as an insertion portion, the valve guide opens at an outer peripheral face of the exposed portion, and also includes a flow passage extending from the exposed portion to the insertion portion, and
• the flow passage is a groove that opens at an outer peripheral face of the valve guide over an entire area from the exposed portion to the insertion portion.