Polyspheric

The Polyspheric engines were V8 engines produced by Chrysler from 1955 to 1958 as lower-cost alternatives to its 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. These were formed by two shallow concave domes where the intake and exhaust valve seats were. Because these engines needed a less sophisticated rocker setup than a true hemi, with only a single rocker shaft in each head, they were also cheaper to produce and lighter. In the Chrysler literature, the Poly engines were also called single rocker shaft (SRS), while the Hemi engines were called dual rocker shaft (DRS). These engines replaced Chrysler's flathead inline-six in the division's lower-priced cars, and were themselves gradually replaced by the Chrysler A engine beginning in mid-1956.

The Polyspheric engines were V8 engines produced by Chrysler from 1955 to 1958 as lower-cost alternatives to its 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. These were formed by two shallow concave domes where the intake and exhaust valve seats were. Because these engines needed a less sophisticated rocker setup than a true hemi, with only a single rocker shaft in each head, they were also cheaper to produce and lighter. In the Chrysler literature, the Poly engines were also called single rocker shaft (SRS), while the Hemi engines were called dual rocker shaft (DRS). These engines replaced Chrysler's flathead inline-six in the division's lower-priced cars, and were themselves gradually replaced by the Chrysler A engine beginning in mid-1956. === 260 === The 260, also known as the 259, displaced and was introduced in the middle of 1955 by Plymouth. It was a bored-out 241, having a bore and keeping the stroke ( ). This engine was also used on 1955 and 1956 Dodge trucks. Maximum power claimed was with a two-barrel carburetor; a four-barrel version with was added later. === 354=== The 354 displaced and was a Poly version of Chrysler's 354 Hemi. Bore and stroke were the same at by , respectively ( ). The 1958 Chrysler Saratoga with four-barrel carberutor (58S) was the most powerful at .

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