Abstract: An improved piston engine includes a rocker arm and a connecting link between the piston rod and the crankshaft to allow its motion to be altered from that of the classic piston engine in order to overcome inherent limitations of the latter and realize greater efficiency. By inserting these two components between the end of a rigidly attached piston rod and a conventional crankshaft, the motion of the piston with respect to the crankshaft can be altered in important ways. For example, the dwell at top dead center can be increased relative to dwell at bottom dead center to the point where they are equal or in fact where dwell at top dead center is greater. Furthermore, because the piston rod is not directly connected to the crankshaft, ignition of the fuel can be timed to occur before top dead center so that pressure is maximized at top dead center in order to improve efficiency. Furthermore, the piston stroke can be shortened and slowed by the geometry of the rocker arm, thus increasing engine life.