The Polyspheric or Poly engines were

V8 engine A V8 engine is an eight-cylinder piston engine in which two banks of four cylinders share a common crankshaft and are arranged in a V configuration. The first V8 engine was produced by the French Antoinette company in 1904, developed and us ...

s produced by

Chrysler Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automoti ...

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 head In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ov ...

s, pushrods, exhaust manifolds and pistons. They were called ''Polyspheric'' or ''Poly'' engines, because they featured polyspherical-shaped (meaning “more than one sphere”)

combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Interna ...

s. 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 The Chrysler A engine is a small-block V8 gasoline engine built by Chrysler with polyspherical combustion chambers. It was produced from 1956 until 1967, when it was replaced by the wedge-head LA engine, although the LA was in production alon ...

, beginning in mid-1956.

Dodge and Plymouth

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).

241

The 241 () was

Plymouth Plymouth () is a port city and unitary authority in South West England. It is located on the south coast of Devon, approximately south-west of Exeter and south-west of London. It is bordered by Cornwall to the west and south-west. Plymouth ...

's ''Poly'' version of the Dodge's 241 ''Hemi'' for 1955. Bore and stroke were the same at by , respectively.

259

The 259 () (also known as the ''260'') was introduced in the middle of 1955 by Plymouth. It was a bored-out ''241'', having a bore and a stroke. It was also used on Dodge Trucks (1955-1956).

270

The 270 () was offered in both Plymouths (1956) and Dodges (1955-1956). Like its predecessors, it was a ''Poly'' version of Dodge's 270 ''Hemi''. Bore and stroke were the same at by , respectively.

315

The 315 () was a ''Poly'' version of Dodge's high-deck 315 ''Hemi''. Bore and stroke were the same at by , respectively. Only used on 1956 Dodge.

325

The 325 () was a ''Poly'' version of Dodge's largest high-deck 325 ''Hemi''. Bore and stroke were the same at by , respectively. Used on 1957 and 1958 Dodge.

Chrysler

The Spitfire engines were ''Poly'' variants of Chrysler's FirePower (''Hemi'') engine. Chrysler built three ''Spitfire'' engines: the ''331 Poly'', ''354 Poly'', and the all-new ''301 Poly'', which did not have a ''Hemi'' version. They were introduced for 1955 in the low-priced Chrysler Saratoga and Windsor models and were used through 1958. All Chrysler Spitfire engines were low deck; no ''Poly'' version of the raised deck

392 __NOTOC__ Year 392 ( CCCXCII) was a leap year starting on Thursday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Augustus and Rufinus (or, less frequently, year 1145 ''A ...

''Hemi'' engine was produced.

301

The 301 () was Chrysler's smallest ''Poly'' engine. Having a bore and a stroke.

331

The 331 () was a ''Poly'' version of Chrysler's 331 ''Hemi''. Bore and stroke were the same at by , respectively.

354

The 354 () 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 .

References

{{Chrysler Group LLC Polyspheric V8 engines