Chrysler A engine

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Chrysler A engine
Also calledPlymouth A engine
Production1956-1961 Mound Road Engine, Detroit, MI
  • 276.1 cu in (4.5 L)
  • 299.6 cu in (4.9 L)
  • 302.5 cu in (5.0 L)
  • 312.5 cu in (5.1 L)
  • 317.6 cu in (5.2 L)
  • 325.2 cu in (5.3 L)
Cylinder bore
  • 3+34 in (95.2 mm; 3.75 in)
  • 3+1316 in (96.8 mm; 3.81 in)
  • 3+78 in (98.4 mm; 3.88 in)
  • 3+2932 in (99.2 mm; 3.91 in)
  • 3+6164 in (100 mm; 3.95 in)
Piston stroke
  • 3+18 in (79.4 mm; 3.13 in)
  • 3+516 in (84.1 mm; 3.31 in)
Cylinder block materialCast iron
Cylinder head materialCast iron
ValvetrainOHV 2 valves x cyl.
Fuel system4-barrel Carburetor
Fuel typeGasoline
Oil systemWet sump
Cooling systemWater-cooled
Power output240–290 bhp (179–216 kW)
PredecessorPolyspheric engines
SuccessorChrysler LA 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 alongside the A from 1964 - 1967. It is not related to the hemispherical-head Hemi engine of the 1950s.

The A engine was first released in 1956 and was used exclusively in Plymouths until 1958 and in Chryslers and Dodges from 1959 on. The Desoto and Dodge 270/315/325 poly was not related to the Plymouth Polys, using the same bottom end as the Dodge and Desoto Red Ram Hemi, but utilizing similar head architecture. The cylinder bore center distance is 4.46 in (113.3 mm), larger than the earlier Dodge-based poly engines. The A engine formed the design basis of its successor, the LA engine, evidenced in the many parts that interchange between the two engine families.[1]



The 277 "Hy-Fire" was the first A-block engine, produced for 1955 in the fall of 1954 and sharing almost nothing but the basic concepts with other engines built by Chrysler. Bore is 3+34 in (95.3 mm) and stroke is 3+18 in (79.4 mm; 3.13 in) for a piston displacement of 276.1 cu in (4,525 cc). It was replaced by the 301 in 1957, except for in low-priced Plaza models where it continued to be used during the 1957 model year.[2] Power for the two-barrel version is 187 hp (139 kW); this increased to 200 hp (149 kW) for the four-barrel "Power Pack" version which also came equipped with dual exhausts.[3] The Power Pack was also fitted to the Facel Vega FV3, of which 48 examples were built in 1956 and 1957.[4]


The Plymouth 301 replaced the 277 in 1957 and kept that engine's 3.125 in (79.4 mm) stroke. Its piston displacement is 299.6 cu in (4,910 cc), thanks to the larger 3+2932 in (99.2 mm; 3.91 in) bore. These dimensions are entirely different from the 1955 Chrysler 301. This engine was also installed in the 1957–1958 Facel Vega FV3B.


The 1956 Plymouth 303 displaces 302.5 cu in (4,957 cc) and uses the same connecting rods as the 277; the bore is 3+1316 in (96.8 mm; 3.81 in) and the stroke is 3+516 in (84.1 mm; 3.31 in).

This engine was used in the following vehicles:


A 313 cu in (5,121 cc) version of the A engine called the 313 was produced from 1957 to 1967 primarily for Canadian and export markets. This engine has a bore of 3.875 in (98.4 mm) and the common 3.3125 in (84.1 mm) stroke, and was used in the following vehicles, amongst others:


The 318 is the most common version of the A engine, produced from 1957 through 1966 in the US and 1967 in some export markets when it was replaced in all markets by the LA 318. Only Plymouth used this 318 in 1957 and 1958, but it was shared with Chrysler from 1959 on and Dodge from 1960 on.[5] It displaces 318.2 cu in (5,214 cc) and has a 3.91 in (99.3 mm) bore and the 3.3125 in (84.1 mm) stroke.

A high-performance version called the V-800, offered in 1957 and 1958, used two four-barrel Carter carburetors to produce 290 hp (216 kW), making it the highest-output factory A engine. It was used in the 1957 and 1958 Plymouth Fury, but was also an option on Plymouth models lower in the model range.

Bristol Cars introduced the 318 in the Mark II model of their 408 (in 1965) and continued to use it in the succeeding 409 and 410 until 1969. From 1962 until early 1965, Checker used this engine for their Aerobus limousines.[6]



The 326 was launched in 1959 Dodges. Its actual piston displacement is 325.25 cu in (5,330 cc) but it was marketed as a 326 to avoid confusion with the Dodge Red Ram 325. The 326 uses the same 3+516 in (84.1 mm) stroke as the 318, but with the largest bore of any A engine at 3+6164 in (100 mm; 3.95 in). It uses hydraulic tappets, unlike the other A engines that used solid, and was used in the 1959 Dodge Coronet.


  1. ^ Lotspeich, Justin. "Poly A Block Parts Interchange". Poly318. Poly318. Retrieved 7 July 2022.
  2. ^ Lee, John (1990). Standard Catalog of Chrysler, 1924-1990. Iola, WI: Krause Publications, Inc. pp. 390–391. ISBN 0-87341-142-0.
  3. ^ "The 1956-1967 Plymouth Polyspherical Head Explained". Eric B. White Digital Documents Library. Automotive History Preservation Society. Archived from the original on 2022-06-29.
  4. ^ "The FVs". Facel Vega Car Club. Archived from the original on 2022-10-03.
  5. ^ Lotspeich, Justin. "Poly A Block History". Poly318. Poly318. Retrieved 7 July 2022.
  6. ^ Naul, G. Marshall (1999). Ron Kowalke (ed.). Standard Catalog of Independents: The Struggle to Survive Among Giants. Iola, WI: Krause Publications, Inc. p. 35. ISBN 0-87341-569-8.

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