The 273 is the engine that founded the Chrysler LA (Light A-series) small-block family. Aluminum-cased lifters, polyspherical-derived combustion chambers, thinwall casting, and dimensions that allowed the same architecture to be punched out to 318, 340, and eventually 360. In 1964–69 production trim it made 180 hp gross with a two-barrel; the 1965–67 Commando 273 four-barrel made 235 hp gross at 5,200 rpm.
By 1970 the 273 had been replaced by the 318 in B-body and C-body cars. It survives in the encyclopedia because plenum decodes some 1968–69 sheets where 273 is still the cell value, and because understanding the 273 is the easiest path to understanding everything that follows in the LA family.