An old idea of how to increase the internal combustion (IC) piston engine power is presented. Such an engine has a 2-side action piston, which divides a single cylinder into two working parts. In these parts there are two usual 4-stroke engines which constitute one double IC engine, equipped with a slider-crank mechanism. The new engine may use bio-fuels as well. The engine may deliver increased power from more compact size - it is estimated to almost double individual levels of the components. The basic technical problem of this solution is sealing and lubrication of the engine, especially sealing of the power head, which is crossed by a rod of the slider-crank mechanism. This is the reason why such an engine has not been manufactured yet, but a modern level of technology may allow manufacturing the engine. The paper is to remind the old idea of how to increase the engine power and additionally to give some propositions of the engine sealing.
