Auxiliary combustion chamber for an internal combustion engine

In an internal combustion engine including a main combustion chamber, an air/fuel mixture intake to the main combustion chamber through the cylinder head, an intake valve for controlling the flow of the air/fuel mixture into the main combustion chamber, and a spark plug for igniting the air/fuel mixture, the improvement comprising:

• an auxiliary combustion chamber including a cavity in the wall of the cylinder head adjacent said air/fuel mixture intake and a shell at least partially lining said cavity and forming a portion of the wall of the said main combustion chamber said shell being integrally cast within the cylinder head for enhancing heat transfer therebetween and said spark plug having its spark gap in the auxiliary combustion chamber;
• at least one unvalved inlet port in said shell interconnecting the auxiliary combustion chamber and the main chamber for conducting air/fuel mixture into the auxiliary chamber and at least one unvalved outlet port in said shell for conducting residual combustion gas from the auxiliary chamber into the main chamber;
• means for retaining said shell in said cavity and means for positioning said shell in said cavity;
• said means for retaining said shell in said cavity including an annular channel formed in the wall of said cavity and a flange formed on the surface of said shell.