EGR Olds 350-455 cu in using std bore 4 bbl carbs – 1973 and later, Reg. To meet Federal Emissions Standards, most 1973 and later vehicles use the EGR Valve to cut down emissions. This valve is bolted directly to the stock manifold on a special boss. This special adapter kit can be used with all stock and high performance manifolds. All Offenhauser 360 degree, Dual Port 360 degree, Port-O-Sonic manifolds will be equipped at the factory with drilled and tapped holes to use the EGR Adapter Kit.