A piston-cylinder assembly of an internal combustion engine is provided which includes a cylinder liner mounted within a bore formed in an engine block, and a cylindrical spacer extending axially and endwise from the liner and coacting therewith to form a cylinder in which a piston is mounted for reciprocatory movement. An end piece overlies an end of the spacer and is supported by the latter. The end piece substantially closes off one end of the cylinder and the piston is in close proximity thereto when at one stroke limit. When the piston is at the one stroke limit, it coacts with the end piece and the spacer to define a combustion chamber. The end piece is secured in assembled relation with the spacer by a first means. A second means is provided for effecting substantial thermal insulating of the block, liner and first means from the heat of combustion which is generated in the combustion chamber during operation of the engine.