Used exhaust manifold spacer with butterfly valve for use on 1967 to mid 1968 Mercury Cougar, Mercury Cyclone, Ford Fairlane, and Ford Mustang with 390 or 427-4V engines. Fully functional, we test these with a heat gun, they do open and close. These thermostat control valve assembly mates to the 1967 and 1968 passenger side 390 exhaust manifold up until about Feb 15, 1968. Easy to tell if it is needed with your manifold, no chamfer for the exhaust donuts at collector? you need this or a plain spacer. These are specific to the above cars. Full size cars, Thunderbirds, and trucks use a different design valve assembly. Ford part number C6OZ-9A427-D.