Ford 351 Cleveland 4bbl Carbie Remflex Exhaust Manifold Gaskets REM3007 Rate_40 Fixed timing test mode for Fixed timing test mode for easy verification of ignition timing accuracy Are you looking for a set of entry level street performance heads for your modern street rod Heating and cooling of the exhaust system causes header and manifold flanges to warp resulting in gaps between the head and header which Remflex exhaust gaskets seal completely due to the thickness and compressibility of the 100 percent flexible graphite There are no rubber binders or composite materials in Remflex exhaust gaskets so they will not shrink or harden due to time or temperature eliminating the need to go back and continually retighten your flange bolts