An opposed-piston, opposed-cylinder OPOC engine is disclosed in which the central axis of the two cylinders is collinear. In four-stroke engines, this is possible with a built up crankshaft. Disclosed are connecting rod configurations that are suitable for a two-stroke engine that can be assembled to a unitary crankshaft, including both pullrods in tension and pushrods in compression. The configuration includes pistons arranged symmetrically, but with offset timing of the intake and exhaust pistons. The offset timing leads to a slight imbalance which can be partially overcome by having the center of gravity of the crankshaft offset from the axis of rotation.