Piston Engine Parts The piston is the automobile engine cylinder body parts in the reciprocating motion of the piston. The basic structure can be divided into top, head and skirt. The top of the piston is the main part of the combustion chamber, the shape of the combustion chamber and the form. The flat piston gasoline engine, the utility model has the advantages of small heat absorption area of diesel engine. The piston top often have a variety of pits, the shape, position and size must be mixed gas and diesel combustion formation and meet the requirements.