Abstract: An article for defining an auxiliary compartment for providing accelerated initial warm-up of the combustion chamber of an internal combustion engine, and thereafter providing for continuous transfer of heat to the walls of the combustion chamber to prevent overheating of the article. The article has a central tubular heat-receiving portion with one end closed and the opposite end open in a generally cup-shaped configuration with a mounting flange provided around the rim of the open end, and a heat output portion of preferably annular configuration provided around the outer periphery of the closed end region. An aperture is provided in the closed end for communicating the interior region of the central portion with the engine combustion chamber. In one embodiment the article is sized and shaped such that the heat output portion is in contact with adjacent portions of the combustion chamber wall to provide continuous transfer of heat from the closed end of the cup to the combustion chamber.