Sierra 18-1917 Block Off Manifold PlateSierra replacement stainless block off manifold plate. Sierra Marine engine parts are manufactured to meet or exceed OEM requirements. Material: Stainless; For Crusader Small Block V8 305-350 cu. in. (Models 220 & 270); For GM Big Block V8 454 cu. in. (Models CH350 & 454XL); Use with: 18-0305 Exhaust Elbow Gasket; 18-0309 Exhaust Elbow Gasket; Interchangeable with: Barr; CR-20-97296; Crusader; 97296; Mallory; 9-40440; Osco; 7296;