invention the modification shown in fig2 is a new camshaft 50 to replace the conventional camshaft 32 the camshaft 50 is constructed to allow the two adjacent piston and cylinder assemblies to be done in phase rather than 180 u00b0 out of phase compared with a conventional camshaft 32 new camshaft 50 has cam lobe 444 positioned on the camshaft in angular alignment with cam lobe 344 alignment therewith this alignment of cam lobes 344 and 444 allows pistons 326 and 426 to complete their combustion strokes simultaneously so that selectively both cylinder 330 and 430 will receive an injection of diesel fuel appropriate to fire both during the following simultaneous power strokes thereof or to alternatively inject only one cylinder 330 and 430 with an appropriate amount of fuel for one of cylinders 330 and 430 to fire alternatively in only one cylinder so that the increased pressure conditions resulting from the one fire can be communicated to the other cylinder that is the passage allows pressure generated by fuel injected and ignited in cylinder 1330 and 430 to be communicated to the other of cylinders 330 and 430 receiving no fuel so the pressure drives both pistons 326 and 426 simultaneously this generates power of both pistons with one less injection charge fig3 shows the modification used to accomplish the communication as shown the modification is simply to remove from the seal engaging surface of the frame 12 extending between cylinders 3 and 4 sufficient material as by grinding or other means to form a passage 52 of a minimum size suitable to enable the communication to take place.