The Polyspheric or Poly engines were V8 engines produced by Chrysler from 1955 to 1958 as a lower-cost alternatives to the Hemi engines. These engines were based on the Hemi engines, using the same blocks and crankshaft parts, but completely different cylinder heads, pushrods, exhaust manifolds and pistons. They were called Polyspheric or Poly engines, because they featured polyspherical-shaped (meaning “more than one sphere”) combustion chambers.