Why didn the 1971 Boss 351 have the thermactor system as the earlier cars did?
[Advanced planning made it possible for the Boss 351 to meet and exceed all government specifications on emissions for 1971. The Improved Combustion (IMCO) system replaces the thermactor system used on the Boss 302. In the thermactor system, an air pump was used to inject additional air into the exhaust manifold to oxidize any unburned hydrocarbon. With the IMCO system, all of the emissions control is achieved by carefully calibrating the carburetor and ignition systems.
