An internal combustion engine can include a piston moving in a cylinder and a junk head disposed opposite the piston head in the cylinder. The junk head can optionally be moveable between a higher compression ratio position closer to a top dead center of the piston and a lower compression ratio position further from the top dead center position of the piston. At least one intake port can deliver a fluid comprising inlet air to a combustion chamber within the cylinder. Combustion gases can be directed out of the combustion volume through at least one exhaust port. One or both of the intake port and the exhaust port can be opened and closed by operation of a sleeve valve that at least partially encircles the piston. Related articles, systems, and methods are described.