Abstract: Improvements to an engine comprise an air compressor cylinder with a piston, a combustion chamber cylinder with a piston. An engine has added an expansion chamber cylinder with a piston. Pistons each have a connecting rod and connecting rod head and associated parts adapted for reciprocating motion via combustion products, and a transmission associated with the engine. Improvements are to the piston seals, ignition assembly, valve shape and stem/rocker, valve operating mechanism, construction of head, heat management/heat shield, connecting rod/piston rotator, engine balancing, fuel pump placement, and a machining process.