Abstract: A valve system is disclosed, which may comprise a valve including a stem, the stem being oriented along a valve axis. Further, a valve guide may be disposed around the valve and may be oriented along the valve axis, and a bearing material may be employed between the stem and the valve guide along less than a full length of the valve guide.

Abstract: A cylinder head is disclosed. The cylinder head may include a body, and a lower jacket formed in a lower portion of the body. The cylinder head may also have a centrally-located fuel injector opening passing through the lower portion of the body, and a plurality of intake and exhaust valve openings spaced evenly around the fuel injector opening. The cylinder head may also include at least one inlet located between adjacent ones of the plurality of intake valve openings or between adjacent ones of the plurality of exhaust valve openings, and at least one outlet located between one of the plurality of intake valve openings and one of the plurality of exhaust valve openings. The cylinder head may further include a plurality of cooling passages surrounding the plurality of intake and exhaust valve openings, and connecting the at least one inlet and the at least one outlet.