Exhaust manifold for an internal combustion engine

An exhaust manifold for an internal combustion engine comprising:

• an inner duct having at least two inlets and one outlet with all of the inner duct inlets being parallel to each other, a separate inlet flange connected to each inlet for mounting said manifold to an engine to receive engine exhaust gases, an outlet flange connected to said outlet for the mounting of an exhaust pipe and an envelope enclosing said inner duct between said inlet and outlet flanges, said envelope comprising two half shells having circumferential edges which are interconnected by a seam and which closely surround said inner duct adjacent said inlet and outlet flanges, but are otherwise spaced from said inner duct so as to provide for an insulating air space between said inner duct and said enclosure, said seam being disposed in the area between said inlets at a substantially greater distance from said inner duct than in any other area such that, in all cross-sectional planes disposed between, and extending normal to, said inlet flanges, said envelope has a drop-like shape.