Used – appears OEM GM correct fitting exhaust manifold heat riser control butterfly valve assembly - P.N. 3746844 – group number GR.3.647 – OEM for 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 Chevy Corvette small and big block block V8 engine – may fit other years as well – no visible casting numbers – 2.5” center hole - verify part number and pictures against your application – slightly dusty former collector’s inventory in vintage OEM condition as shown – some minor surface corrosion and patina from sitting in storage as shown - counter weight appears OEM cast - body appears newer machined steel as shown