A water jacket for a cylinder head of an internal combustion engine includes a coolant chamber arranged to permit the flow of coolant within the water jacket and a coolant conduit positioned to permit the flow of coolant proximate to a recess for receiving an exhaust valve mounted to the cylinder head. The coolant conduit is in fluid communication with the coolant chamber, and the coolant conduit is shaped as a complex curve. A water jacket includes a pair of apertures arranged to receive a spark plug and a fuel injector. The apertures are separated by a separating member, and a coolant chamber is arranged to permit the flow of coolant about the apertures. The separating member includes a coolant channel in fluid communication with the coolant chamber so as to permit the flow of coolant between the apertures.