S&S Intake Manifold Conversion Kit For Harley Big Twin Features Kit converts stock manifolds to a more rigid-mount system Internally-polished manifold replaces the stock unit for maximum air-flow and increased horsepower Eliminates cracking and leaking problems associated with them Includes an S&S Performance manifold, mounting flanges, two specially molded O-rings and two .350 spacers for spacing out the stock air cleaner or carb mount bracket Can be used with S&S Super B and E carburetors as well as stock carburetors with a two bolt mounting pattern Must be used with 3/8 thick insulator block with 1-7/8 opening 401-347