The Chrysler FirePower engine family, known as the early Hemi, supplanted the Ford flathead V8 in many 1950s hot rods.
Chrysler released its first automobile FirePower V8 in 1950 for the 1951 model year. Its hemispherical combustion chambers supported large valves and efficient breathing, giving the engine a strong performance reputation. The first-generation family included 331, 354, and 392-cubic-inch Chrysler versions.
In the 1950s and early 1960s, rodders valued the FirePower as a powerful alternative to the aging Ford flathead. Its overhead-valve layout and Hemi combustion design offered more potential than the flathead architecture, although the Chrysler engine was heavier and physically larger.
“Early Hemi” is a later enthusiast label rather than the original Chrysler marketing name. Chrysler called its version FirePower; DeSoto used FireDome, and Dodge used Red Ram. That distinction makes “Chrysler FirePower” the precise answer, rather than the broader word “Hemi” alone.