Internal combustion engines having multi-stage telescoping poppet valves in lieu of conventional poppet valves are disclosed. The engines may have pistons with a skirt with a field of pockets that provide a ringless, non-lubricated, seal equivalent. The piston heads may include one or more depressions and may be domed to facilitate the movement of air/charge in the cylinder. The engines may also have non-circular, preferably rectangular, cross-section pistons and cylinders. The engines also may include a split crankshaft. The engines may use the pumping motion of the engine piston to supercharge the cylinder with air/charge. The engines also may operate in an inverted orientation in which the piston is closer to the local gravitationally dominant terrestrial body's center of gravity at top dead center position than at bottom dead center position.