a multi cylinder internal combustion engine is disclosed including a crank shaft housing and a crank shaft connected to a plurality of pistons which reciprocate within the cylinders the cylinder housing is vertically mounted to the crank shaft housing a plurality of concentric sleeves are arranged within the cylinder housing and enclose a plurality of pistons and cylinders arranged in tandem the concentric sleeves are connected to a selected number of cylinders and to the crank shaft for rotating the crank shaft responsive to reciprocal movement of the pistons and cylinders application_number US 40733782 A description turning first to fig1 the preferred embodiment of the invention is shown the reference numeral 10 generally designates the housing for the cylinders and pistons the housing 10 is mounted on the crank shaft housing 12 as shown and closed at its opposite end by the end wall 14 the housing 10 has a cylindrical shape and appears much longer than the customary engine cylinder within the housing 10 are a number of pistons and cylinders selectively secured to a plurality of sliding sleeves which are concentrically arranged about the cylinders and pistons six cylinders and pistons are shown in fig1 for illustrative purposes only it is understood that.