Abstract: Monoblock engine/air compressor combinations, particularly those providing high pressure gas, experience problems in lubricating the piston pins connecting the compressor piston assemblies to the engine connecting rods. To alleviate this problem, additional weight is added to the compressor piston assemblies to force a load reversal at a determinable point in the piston cycle just after top dead center, thereby facilitating lubrication of the piston pins. An equation is disclosed for calculating the weight of the compressor piston as a function of the compressor gas pressure, geometry of the rotating components and engine speed. In another aspect of the invention, weight is added to the engine flywheel to balance an unbalanced compressor piston after the additional weight has been added.