An improved internal 
combustion piston engine that utilizes, in combination at least one 
poppet valve 52 of known type and a 
sleeve valve 5 to affect the functions of intake and 
exhaust gas flow. The resulting gross increase in valve area and 
volumetric efficiency enables the engine to produce high specific power without large 
valve opening durations or valve overlap and the 
resultant undesirable increase in 
low speed pollution and torque reduction.One embodiment of this invention will use the at least one 
poppet valve 52 as an intake valve, and the 
sleeve valve 5 as an 
exhaust valve. Another embodiment of this invention will use the at least one 
poppet valve 52 as an 
exhaust valve, with the 
sleeve valve 5 performing the intake valve function.Additionally, the sleeve valve may be either constantly or intermittently or incrementally moved to open or close a port through described methods. Intermittent movement of the sleeve valve may be controlled by a computer 77 in known manner, a novel 
advantage being that a relatively small amount of energy is required for this function because the sleeve is largely moved by friction with the 
piston 46 or associated parts 47, 48, 49.Another novel feature is the use of engine oil instead of a 
water based coolant to control heat in the cylinder sleeve area 10. This minimizes friction and significantly simplifies 
cylinder block design and manufacture.The use of poppet valves which are either intake or exhaust valves simplifies 
cylinder head design, and the 
elimination of cold and hot valve and port areas in the 
confined space of a 
cylinder head reduces the complexity of design for use of 
ceramic materials.