The Chrysler Hemi is a hemispherical combustion chamber. Three different types of Hemi engines have been built by Chrysler for automobiles: the first (known as the Chrysler FirePower engine) from 1951 to 1958, the second from 1964 to 1971, and the third beginning in 2003. Although Chrysler is most identified with the use of "Hemi" as a marketing term, many other auto manufacturers have similar designs.
During the 1970s and 1980s, Chrysler also used the Hemi name for their Australian-made Hemi-6 Engine.
Arguably, the best known/most famous is the second generation produced from 1964 - 1971. It was used as a basis for many of the custom built drag racing engines (see Ed Pink &/or Keith Black) then & is still used today. It displaced 426 cubic inches & was rated at 425 HP from the factory stock. It was nicknamed 'The Elephant'.