channel near the valve chamber and rotatable from outside the engine to change the cross sectional dimensions of the inlet channel and increase or decrease the twist in the flow of combustion air therepast application_number US 13553380 A description an air cooled cylinder head portion 1 of a valve controlled internal combustion engine constructed in accordance with the present invention is shown in fig1 to include a combustion chamber inlet valve 8 composed of a head 7 mounted on an elongated valve shaft 5 the valve shaft 5 being movable within a guiding core 13 positioned within the cylinder head 1 so as to cause the head 7 to suitably open and close the opening in the bottom surface 6 of the cylinder head 1 leading into a combustion chamber of the internal combustion engine not shown the cylinder head 1 also includes a valve chamber 4 which extends upwardly from the bottom surface 6 of the cylinder head and concentrically around the valve shaft 5 as well as a curved inlet channel 2 which communicates downwardly between the top surface 3 of the cylinder head and the valve chamber 4 the inlet channel 2 being shaped so that combustion air will be caused to flow in a twisting fashion around the axis of the valve shaft 5 which also represents the axis of the piston located in the combustion chamber not shown as it moves from the cylinder head top surface 3 to the valve chamber 4 also included in the cylinder head 1 is a bore through which slidingly extends an adjustable air flow control element 9 as can be.