An exhaust valve comprises a substantially tubular body extending along an extension axis, a substantially flat flap, and a shaft integral with the flap and rotatable about a rotation axis between a closed orientation and an open orientation. The exhaust valve further includes a first seat suitable for accommodating a first edge of the flap facing the first seat, and a second seat suitable for receiving a second opposing edge of the flap. In each plane passing through the extension axis, a distal end of a profile of a seat is curved in the direction of the opposing edge until the distal end comes into contact with the opposing edge. A distal end of a profile of an edge is curved in the direction of the opposing seat until the distal end comes into contact with the seat.