A CYLINDER HEAD FOR A LEAN-BURN GASOLINE ENGINE

A lean-burn gasoline engine (110), comprising an air intake port having an air intake port inlet, an air intake port outlet, and an air channel (45) connecting the air intake port inlet to the air intake port outlet, a combustion chamber (50) having a combustion chamber inlet being connected to the air intake port outlet, the combustion chamber inlet having a throat where the air intake port outlet meets the combustion chamber inlet, a movable valve (51) comprising a valve head top surface (62) that faces the air intake port and a valve stem (63), the movable valve (51) being arranged to move between a closed state for closing off the combustion chamber inlet and an opened state wherein intake air can flow from the air intake port into the combustion chamber (50), a valve guide opening (69) in a wall of the air channel opposite the top surface (62) of the movable valve (51), and a valve guide passage (66) extending into the wall and away from the valve guide opening (69), the valve guide passage (66) housing a valve guide (65) arranged to guide the valve stem (63) and permit movement of the movable valve (51) between the closed state and an opened state. The valve guide (65) has a first end proximate the movable valve being positioned within the valve guide passage (66) such that airflow through the air channel (45) is not impeded by the valve guide (65).