moreover is designed for snap together construction at end 42 tube 34 has a rib 74 that extends circumferentially around the enlarged diameter portion 43 and engages an undercut 76 that extends circumferentially around bore 20 as depicted by fig1 a pair of fins 68 extend from the outer surface of the center body and stop just short of contacting the inside of bore 20 another pair of fins 70 extend radially outward from the sides of center body 34 and as shown by the partial section of fig2 each fin 70 is received in a groove 72 formed in the inner surface of housing 10 fins 68 and 70 and the grooves 72 may be alternately located on the inner surface of housing 10 and the center body 34 fig2 also shows an arrangement of ribs 77 that are used to support disc 50 in a manner similar to ribs 40 and hereinafter described fins 70 and groove 72 align chord member 38 and bar 28 to cause disc 50 to bend about its centerline only thereby facilitating proper sealing of disc 50 against the exhaust tube the valve is easily assembled by first placing discs 50 and 52 over pins 46 and 48 and then sliding the exhaust tube into the housing through the exhaust port the exhaust tube has a wider diameter across fins 70 than the inside diameter of bore 20 the greater overall diameter of fins 70 prevents the tube from being inserted into the housing unless it is in the proper rotational position as the tube is slid into.