A passive exhaust valve assembly includes an exhaust conduit that has a first pipe section attached in generally axial alignment with a second pipe section. The end portion of the first pipe section includes a circumferential segment disposed within the end portion of the second pipe section to form an overlapping interface. The end portions of the first and second pipe sections each include a flange protruding radially outward from the respective first or second pipe section, whereby the flanges engage with each other to form an axle seat therebetween. A support shaft extends laterally across an interior volume of the exhaust conduit and rotatably engages the axle seat. A valve plate is coupled to the support shaft within the interior volume of the exhaust conduit for moving relative to the exhaust conduit between open and closed positions.