Polyspheric engine
| Polyspheric | |
|---|---|
| Overview | |
| Manufacturer | Chrysler |
| Also called |
|
| Production | 1955-1958 |
| Combustion chamber | |
| Configuration | 90° V8 |
| Displacement |
|
| Cylinder bore |
|
| Piston stroke |
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| Cylinder block alloy | Cast iron |
| Cylinder head alloy | Cast iron |
| Valvetrain | OHV |
| Combustion | |
| Fuel system | Carburetor |
| Fuel type | Gasoline |
| Oil system | Wet sump |
| Cooling system | Water-cooled |
| Chronology | |
| Predecessor | Chrysler flathead engine |
| Successor | Chrysler A engine |
The Polyspheric or Poly engines were V8 engines produced by Chrysler from 1955 to 1958 as 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. These combustion chambers were formed by the two shallow concave domes where the intake and exhaust valve seats were.
Because these engines needed a less sophisticated rocker setup, with only a single rocker shaft in each head, they were also cheaper and lighter than their Hemi counterparts. 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, but were slowly replaced by the Chrysler A engine, beginning in mid-1956.
Dodge and Plymouth both offered Poly versions of Dodge's Hemi engine. The Dodge versions were marketed as Red Ram or Super Red Ram (internal code A388).
The 241 (241 cu in (3.95 L)) was Plymouth's Poly version of the Dodge's 241 Hemi for 1955. Bore and stroke were the same at 3.4375 in (87.31 mm) by 3.25 in (83 mm), respectively.
The 260 (also known as 259) (259 cu in (4.24 L)) was introduced in the middle of 1955 by Plymouth. It was a bored-out 241, having a 3.5625 in (90.49 mm) bore and a 3.25 in (83 mm) stroke.
The 270 (268 cu in (4.39 L)) was offered in both Plymouths and Dodges. Like its predecessors, it was a Poly version of Dodge's 270 Hemi. Bore and stoke were the same at 3.625 in (92.1 mm) by 3.25 in (83 mm), respectively.
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Wikipedia