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Home/Technical Info/Chrysler & Imperial/01. Engines/ 1951-1958 Early Hemi 331-392 V8/
History of the Early Chrysler Hemi V8 (1951-1958)

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Chrysler applied their WWII experience with the hemispherical combustion chamber and used it to develop their first overhead-valve V8 engine, released in 1950 for the 1951 model year under the name "FirePower", not "Hemi", (the spelling is correct with the "P" capitalized) the early hemi was never called "Hemi" by Chrysler. The first version of the FirePower engine had a displacement of 331.1 cu in and produced 180 HP.

All early Chrysler FirePower hemi engines have a bore center distance of 4.5625", larger than any other Chrysler engine except the B/RB engine. All Chrysler FirePower engines are "oversquare"; meaning that the bore is larger than the stroke. The early Hemi was released in three displacements for the period 1951-1958: 331; 354; and 392 cu. in.

331 Hemi (1951-1955)
This was first FirePower engine, used from 1951 to 1955. It had a deck height of 10.37", a bore of 3.8125" and a stroke of 3.625" for a piston displacement of 331 cu in. The first versions used a two-barrel carburetor and produced 180 HP in the years 1951-53. For 1954 the Hemi was offered in 2 and 4-barrel versions making 195 and 235 HP respectively.

In 1955, the Chrysler 300 version was added with 2 4-barrel carburetors. The engine made 188, 250 and 300 HP in these configurations. The 331 engine was used in the following applications:

  • 1951-1955 Chrysler New Yorker
  • 1951 Chrysler Saratoga (optional)
  • 1952 Chrysler Saratoga Club Coupe (optional)
  • 1952 Chrysler Imperial Parade Phaeton
  • 1951-1954 Chrysler Imperial and 1955 Imperial
  • 1955 Chrysler 300

354 Hemi (1956)
The 354 cu. in. version was released in 1956 in response to the competition's large eincreases in engine displacement. It used the same deck height as the 331, but had a bore of 3.9375" and the same stroke of 3.625". It was used in the 1956 New Yorker, Imperial Custom and Crown, and Chrysler 300B.

The 300B engine was rated at 340 HP, while the New Yorker and Imperial 354 engine configuration produced 280 HP. No 2-barrel version was offered from this point forward, with "economy versions of the block running "Polyspheric" heads instead of the more complex and expensive Hemi heads. The 300B could be had with an optional 355 HP high performance version, making it the first American V-8 to be rated at one horsepower per cubic inch.

The 354 was a short-term Hemi, being in place for only this one year. The 354 block continued through 1958 using the Polyspheric heads and was called the Chrysler "Spitfire V8". This was used in the Chrysler Windsor and Saratoga models from 1955-1958. (To see more about the Polyspheric Chrysler engines, click here).

392 Hemi (1957-1958)
In 1957 the 392 was stroked from 3.625" to 3.906". This new longer stroke block was released and was used through 1959 (in the Imperial Crown only). It had a 4.00" bore and 3.906" stroke. The deck height was raised to 10.87", which was 0.5" taller than that of the previous blocks. Because its deck was taller, Chrysler cast the 392 heads wider in the intake side so that earlier manifolds could be used with the new tall deck block. The 392 was used in the 1957-1958 New Yorker, 1957 Chrysler 300C, 1958 Chrysler 300D, and 1957-1958 Imperial.

In 1957, Chrysler offered the 392 at 325 HP with 9.25:1 compression for the New Yorker and Imperial. In 1958 it was only issued as a 10:1 compression, 345 HP version in the non-performance cars - again using a single four-barrel carburetor.

The dual four-barrel version of the 392 was available in the 1957 Chrysler 300C & 1958 300D. This engine was rated at 375 HP in '57 and 380 HP in '58. In 1957, a special high performance Hemi was offered for the 300C, and this engine was rated at 390 HP. It required a manual transmission (3-speed) due to concerns about torque damaging the automatic trans (unfounded, as it turned out).

The special high performance engine was again offered in 1958. It was an extremely rare piece and only available on 16 300Ds. This option used Bendix "Electrojector" electronic fuel injection. When so equipped, the high performance 392 was rated at 390 HP. Due to reliability problems with the primitive onboard computer which controlled the injection, however, 15 of the 16 300D cars built with this option were recalled and retrofitted with the dual 4-barrel carburetor setup. The remaining car that did not have the system removed was located and has been restored.

From 1959 forward, the Chrysler line only was fitted with either the corporate "B" or "RB" (raised deck B) wedge V8, thus ending the "Hemi" era for Chryslers.

The newer Hemi released in 1964 would only find it's way into Dodge and Plymouth mid-sized cars. It would not be until 2005 that the Hemi would return to Chryslers - in the modern 300C.

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