Wallstreetman, I think you misunderstand the point I'm making. The 426 indeed did convert a lot of gasoline into power. However, it also released a lot of unburned hydrocarbons. The same is true of the 440 Mag and the 383 Mag. As I recall, all those engines were out of production by 1973 -- before the gas crisis but after the imposition of tighter emissions laws.