Ah, here's a source of confusion. Chevrolet made a 400 cubic inch Small Block Chevy engine. It was considered for use in the 1972 Z28, but this was never done. The 400 was commonly used in full size cars, station wagons, Chevelles and trucks. Chevrolet also made a 396 Big Block Chevy engine. From 1970 to 1972 this engine was installed in some Super Sport Camaros. However in 1970 this engine was overbored .032" so it was technically a 402 cubic inch engine. It was badged as a 396 if installed in a Camaro. At the time, GM/Chevrolet had a policy or limit of "400" cubic inch or greater engines being installed only in mid or full size cars - not the Camaro. This is why the LS6 idea was deep-sixed as well.