The Chrysler B and RB engines are a series of big-block V8 gasoline engines introduced in 1958 to replace the Chrysler FirePower (first generation Hemi) engines. The B and RB engines are often referred to as "wedge" engines because they use wedge-shaped combustion chambers; this differentiates them from Chrysler's 426 Hemi big block engines that are typically referred to as "Hemi" or "426 Hemi" due to their hemispherical shaped combustion chambers.