The tables below detail the starting engine serial numbers used on the 1950s Mopar Hemi engines (often referred to as the "old style" hemi). These are easily differentiated from the new (426) Hemi motors in that the old motors had the distributors located to the rear of the carburetor, similar to the old small blocks.
The information presented below is probably not to be considered 100% complete, but it may help in identifying that mystery motor in grandpa's garage!
Webmaster's note. See A-engines, Sonoramic, Polyspherical engines; 392 C300 engine; the origins of the Hemi
also see a full article on the original Hemi - its development and applications.
And be sure to read the corrections below the table.
* Robert Hovland wrote: “There was a 300 HP 331 engine built for the 1955 Chrysler C300, the first model year for the 300. In addition, two different displacement engines are listed for 300s for 1956 and 1957. To the best of my knowledge, there was only one displacement hemi engine for each model year of Chrysler passenger gars for each and every year from 1051 through 1958.
The polysphere engine which came out as a 301 cubic inch engine in the 1955 Windsor was used in the non-hemi Chryslers in the 1955-1958 model years. This Polysphere engine, called the Spitfire, became a 331 in the 1956 Windsor(225 HP in the Windsor, 2 barrel carb, 250 HP optional and with a WCFB four barrel carb), and became a 354 in the 1957 and 1958 Windsor and Saratoga models (285 HP in the 57 Windsor with a 2 barrel carb, 295 HP in the 57 Saratoga with an AFB four barrel, 290HP in the 58 Windsor with a 2 barrel carb, 310 HP in the 58 Saratoga with an AFB four barrel. So, you better look at your data once more; you should find that the Hemi for US Chrysler passenger cars was 331 from 1951-55, only 354 in 1956, and only 392 in 1957 and 1958.
The 1956 300 had an optional engine rated at 355 HP and it was not recommended for normal street driving. There may have also been an optional engine (different cam) for the 57 300--I'm not sure. On the 58 300s there was also a very limited production option of Bendix fuel injection available on the 300D engine; I'm not sure what the horsepower rating was on this engine.
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