Abstract: An engine is disclosed that is applicable for automotive and truck use but is also adaptive for other power producing uses. Two reciprocating cylinders are housed within an outer cylinder. A piston is housed within each of the two reciprocating cylinders. The reciprocating cylinders are so designed that after combustion in one reciprocating cylinder, the movement caused by the combustion will aid in setting up the circumstances combustion in the opposing compression chamber formed by the opposing reciprocating cylinder and opposing piston. Due to this design, the horizontal reciprocating movement is continuous and all of the horizontal movement caused by the combustion in both opposing reciprocating cylinders and both opposing pistons is useful. The horizontal movement of the reciprocating cylinders and pistons is translated into rotational energy in the crankshaft by three scotch yokes, each scotch yoke housing a scotch block, each scotch block in turn surrounding one crankthrow.