a valveless four stroke internal combustion engine employs an intake piston and an exhaust piston that reciprocate within intake and exhaust cylinders disposed adjacent the combustion chamber of the engine a power piston reciprocates within a cylinder that defines a portion of the combustion chamber an intake port opens into the intake cylinder and an exhaust port opens into the exhaust cylinder upon reciprocation of the intake and exhaust pistons the exhaust ports will be covered and uncovered by coordinating movement of the intake and exhaust pistons with reciprocation of the power piston a combustible fuel air mixture will be drawn into the combustion chamber ignited and exhausted the timing and extent of movement of the intake and exhaust pistons can be controlled by a crankshaft or cams application_number US 54505395 A description referring to fig1 3 a four stroke internal combustion engine is indicated generally by the reference numeral 10 the engine 10 has a crankcase 12 to which a cylinder 14 is attached as illustrated the cylinder 14 is air cooled although water cooling is possible and will be used in many applications a power piston 16 is disposed within the cylinder 14 for reciprocating movement therein a crankshaft 18 having a crankpin 19 is mounted for rotation within the crankcase 12 the crankpin 19 is connected to the piston 16 by means of a connecting rod 20 a flywheel 22 is mounted to the crankshaft 18 a spacer 24 is mounted atop the cylinder 14 so as to define a portion of a combustion chamber 25 a spark plug 26 is threaded into an opening into the spacer 24 so as to extend into the combustion chamber 25 a cylinder head 28 is mounted atop the spacer 24 the cylinder head 28 includes an intake cylinder 30.