Abstract: A process for elimination of a conventional head gasket as typically utilized in an internal combustion engine, and more particularly in a motorcycle engine, is set forth wherein the cylinder head is removed from the associated engine block. The cylinder head is formed with a coaxially aligned groove of rectangular cross-sectional configuratiion. A complementary groove of equal diameter and axially aligned with the groove formed about the combustion chamber is formed into the engine block. An "O" ring of a cross-sectional area greater than that of the combined cross-sectinal area of the groove formed in the cylinder head and of the groove in the engine block is positioned within the grooves whereupon securement of the cylinder head to the engine block compresses the "O" ring within the aligned grooves to effect sealing of the engine block to the groove.