A process for producing exhaust gas manifolds is provided, which have a flange for fastening to the cylinder head of an internal combustion engine, manifold pipes for leading off the exhaust gases flowing from the cylinders, and a pipe connector, wherein the pipe connector has openings for the manifold pipes. In accordance with the invention, the pipe connector is designed with reinforced openings. Then the ends of the manifold pipes are introduced into the openings and expanded. In this process, the pipe ends undergo plastic deformation, and the pipes are connected gas-tight.