Back in the early ’90s, when Chrysler realized that it would need a new truck motor to replace its 318/360 Magnum engines to meet the coming emissions standards, the company considered two pushrod engines along with one SOHC design and concluded that a pushrod motor with a pair of HEMI heads that really breathed would make a great truck engine and could still be used in its cars. This is how the 5.7L Gen III HEMI was born in 2003.
Chrysler made the Hemi engine famous. They didn’t invent the hemispherical chamber, but they were the first to build an engine with a hemi chamber for an American car back in 1951. They originally called it the “Double Rocker Shaft V8,” but it soon became “the Hemi.”