Initially introduced as the Dodge Red Ram Hemi, this Hemi was a six-cylinder in 1953, but a Hemi V8, based on the 1951 Chrysler Hemi, followed in short order, but it had a smaller displacement for the lighter weight Dodge family. None of the major components were interchangeable with any other Chryco subsidiary product. This early version had a bore center of 4.1875 inches (106.4mm), which was the smallest Hemi made.
The Dodge division offered a lower powered, less technical polyspheric (poly) head designed from ’55 to ’58, which used a single rocker shaft configuration in the heads. This design also appeared in the DeSoto and the top-line Plymouth models for the ’55 and ’56 model years.
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Also marketed by Dodge in ’53 was a lower compression (ratio=7.1:1), 24-cubic-inch Hemi with a bore of 3.4375 inches and a stroke 3.25 inches long, which produced 140 bhp (104 k/w). This wasn’t the same engine as the Plymouth 241, which used the hybrid poly head design.
Marketed as the Dodge 270 for the ’55 and ’56 model years, the 268-cubic-inch (4.4L) inline engine was available on the high-end models, including the Dodge Meadowbrook and with its 7.5:1 compression ratio developed 150 bhp (112 kw). This power plant is different from the Plymouth and the Dodge Coronet 270, which had a lower compression (7.1:1) poly head engine producing 140 bhp (104 kw).
In 1956, Dodge offered a larger 315-cubic-inch (5.2L) power plant that had a longer 3.80-inch ( 96.5mm) stroke and used a raised deck block with the polyspherical heads. There was an optional D-500 version of this engine with a four-barrel carburetor and larger valves; this unit was a Hemispherical design. The Dash 1 or D-500-1 had an aluminum intake manifold with a pair of Carter WCFB carburetors mounted on top and was available as a “racing only” package although this head was identical in size and shape to the base 500-1 models. The carburetor was the same as the one used for the base Chrysler 300B and the DeSoto Adventurer.
For the 1957 model year, Dodge developed a 325-cubic-inch engine, and the base offering was a poly head called the KDS, which had a 3.6875-inch (93.7mm) bore with a 3.80-inch (96.5mm) stroke. The higher performance 325, the KD-500, was a Hemi design. There was also a rare extra high-performance KD-500-1 version, which sported two four-barrel carburetors. These engines all have mechanical valves, but the Hemi version had the dimples in the valve covers to accommodate the clearances for the adjusters on the mechanical valves.