Cooling water passage in engine cylinder head

A cooling water passage in the cylinder head (22) of engine to evenly absorb heat to prevent deformed mechanical parts has a spacer (26) between cylinder and cylinder head (22), a water connection port on the exhaust passage side of the spacer (26), cooling water flowing through the port into the cylinder head and limited by a retainer (224) to extend the flow route, the cooling water first passing the exhaust passage side at a higher temperature before cooling the inlet passage side at a lower temperature to upgrade the cooling effects.