Abstract: A structure of an exhaust manifold branch collecting portion includes a double collecting pipe 21 for collecting a plurality of exhaust openings 11A, 17A. The double collecting pipe 21 is comprised of an inner pipe 21-1 and an outer pipe 21-2, which are connected integrally to each other. In a space formed between the inner pipe 21-1, the outer pipe 21-2, and a ring-shaped stainless steel cushion member 22-2, a tubular cushion member 22-1, which is thermally expanded and foamed, is arranged as a restricted cushion structure.

Abstract: A structure of an exhaust manifold branch collecting portion includes a double collecting pipe 21 for collecting a plurality of exhaust openings 11A, 17A. The double collecting pipe 21 is comprised of an inner pipe 21-1 and an outer pipe 21-2, which are connected integrally to each other. In a space formed between the inner pipe 21-1, the outer pipe 21-2, and a ring-shaped stainless steel cushion member 22-2, a tubular cushion member 22-1, which is thermally expanded and foamed, is arranged as a restricted cushion structure.

Abstract: A spiral gasket apparatus, capable of being held on an inclined flue gas outflow pipe without falling off therefrom, is constructed by winding a metal hoop member and a filler member, superposed on each other. A part of the hoop member from the beginning extremity of the hoop member on the inner side, which is wound as many as several turns to a welded fixed portion thereof, is raised inward by using the welded fixed portion as a fulcrum. An extremity portion thereof is folded back to form a superposition part. Since the raised part of the hoop member acts as a spring and is brought elastically into contact with an inclined flue gas outflow pipe, the gasket is held on the flue gas outflow pipe.