A combustion chamber arrangement for two-cycle or four-cycle internal combustion engines, where the traditional piston is replaced by a reciprocating disk that, together with the cylinder wall, creates two sealed combustion chambers for separate combustion cycles. In each combustion chamber a traditional combustion cycle takes place, such that two complete combustion cycles occur within overlapping cylinder volumes. In a four-stroke version, the cylinder produces power on two out of every four strokes. In a two-stroke version, the cylinder produces power on every stroke. The reciprocating disk is connected to two rods that extend through the ends of the cylinder. A power transmission rod transfers combustion power to a standard crankshaft, or through gears to a drive shaft, and a balance rod balances the pressure area on the two sides of the reciprocating disk. A special bushing seal configuration inhibits leakage at the end of the cylinders about the rods, and in some cases the power transmission rods of multiple cylinders are coupled to a common connecting rod by a power transmission bridge spanning the cylinders.