Many Consider Hemi Engines Second To None
Hemi is now inexorably linked to Chrysler’s combustion chamber design, despite not being the first company to use it. Here’s a brief history of the Hemi.
A development P-47 Thunderbolt powered by the first Chrysler Hemi. Reportedly capable of over 500 mph, it was doomed by the advent of jet aircraft.
The first Chrysler Hemi was actually the massive 36 liter XIV-2220 inverted V-16 aircraft engine developed by Chrysler during World War II (but never went into production). The engineers who worked on the project gained valuable experience with cylinder head gas flow which they later applied to somewhat smaller engines.
To keep things simple, we’ll refer primarily to the three generations of Hemi engines. Generation I were the models built for various Chrysler Corp. nameplates throughout the 1950s. Generation II was the 426 “Elephant Motor” created for NASCAR racing in 1964 and sold to the public in passenger cars starting in 1966. The engine was revived and updated as part of a Mopar crate engine program. Generation III are the Hemi engines that are being produced today.
In 1951, Chrysler introduced their new line of V8 motors, popularly known as the Hemi, because the combustion chamber was fully machined into the shape of a 1/2 dome or hemisphere. The intake and exhaust valves were located on opposite sides of the combustion chamber at 90 degrees to the cylinder bore axis, so separate individual rocker shaft assemblies (two on each head) were necessary to operate and control all sixteen Intake and Exhaust valves. It also centralized the spark plug location,making the flame travel shorter, thus more effective in lighting off the air/fuel mixture.
It also gave the combustion chamber, greater thermal efficiency. These engines run cooler because of having a greater surface for heat transfer along with large cooling passages. This design also allowed higher compression ratios, due to its larger volume. Hemi cylinder designs utilize two rocker shafts per head and a complicated valve train. This process proved to be extremely costly and would eventually exceed production costs. Phasing out the Hemi head in the late 1950s in lieu of a much cheaper wedge head design was inevitable.
Apollo 11 astronauts ride through ticker tape parade in NYC in a 331 FirePower V8 Chrysler Imperial Parade Phaeton
This first FirePower engine, used from 1951 to 1955, displaced 331 cu in (5.4 L). Most used a two-barrel carburetor and produced 180 hp, with the exception of the 1955 Chrysler C-300 which was equipped with dual four-barrel carburetors and produced 300 hp.
The 331 engine was installed in the following models: 1951–1955 Chrysler New Yorker, 1951–1954 Chrysler Imperial, 1955 Imperial. 1952 Chrysler Imperial Parade Phaeton, 1955 Chrysler C-300A, well as optional on the 1951 Chrysler Saratoga, and the 1952 Chrysler Saratoga Club Coupe
The 354 CID engine was released in 1956, The 300B engine was rated at 340 hp with an optional 355 hp version available, making it the first American V-8 to be rated at one horsepower per cubic inch. The New Yorker and Imperial 354 engines produced 280 hp.
The Hemi was optimized for truck service as well. These were available with one or two four-barrel carburetors, and were offered in Dodge’s heaviest duty models as the ‘Power Giant V-8’ from 1957 through 1959; they were the largest of four hemi truck engines offered by Dodge in the 1950s.
The 354 engine was used in the following applications:
1956 Chrysler New Yorker
1956 Chrysler 300B
1956 Imperial Custom & Crown
1957 Dodge D-501
1957–1959 Dodge C Series Pickup
The 392 raised-deck engine released in 1957 was offered in two configurations: 325 hp with 9.25:1 compression and 345 hp with 10:1 compression, both with a single four-barrel carburetor. A dual four-barrel version of the 392 available in the 1957-58 Chrysler 300C & 300D cars was rated at 375 hp.
A rare option available on the 1958 300D was Bendix “Electrojector” fuel injection, with which the 392 was rated at 390 hp. Due to reliability problems with the primitive onboard computer which controlled the injection system, however, 15 of the 16 300D cars built with the fuel injection option were reportedly retrofitted with carburetors.
The 392 engine was used in the following applications:
1957–1958 Chrysler New Yorker
1957 Chrysler 300C
1958 Chrysler 300D
DeSoto’s Hemi engines were called Fire Dome.
In 1952, DeSoto introduced its version of the FirePower with a displacement of 276 CID (4.5 L). Power output was 160 hp . It was a hot seller, with 50,000 vehicles using the engine until it was replaced in 1954.
An increase in displacement to 291 CID (4.8 L) was made for 1955 by increasing the bore slightly.
The DeSoto engine was enlarged for 1956 to 330 CID (5.4 L).
Under the hood of a 1956 DeSoto Adventurer
Displacement was increased again for 1956 (DeSoto Adventurer only) and 1957 (Firedome and Fireflite models) to 341 CID (5.6 L). The DeSoto Adventurer produced 343 hp using dual four-barrel carburetors.
The largest DeSoto engine for 1957 was the DeSoto Adventurer at 345 CID (5.6 L). Equipped with dual four-barrel carburetors the engine produced 345 bhp.
Dodge’s Hemi was introduced in 1953 as the Red Ram.
Dodge did not have a V8 engine until one was developed specifically for the line in 1953 based on the 1951 Chrysler Hemi design, but down-sized for these smaller cars. They do not share any major dimensions or components with the larger Chrysler and DeSoto Hemi engines.
Dodge introduced the 241 CID (4.0 L) engine in 1953. With a low compression ratio of 7.0:1 the 241 produced 140 hp. For 1954, the more premium Dodge engines generated 150 hp thanks to a higher 7.5:1 compression ratio. The 241 only lasted two years, being replaced by the 270 for 1955.
Displacing 270 CID (4.4 L) the engine was used in the 1955 and 1956 Dodge premium vehicles. In the Dodge Coronet, with a 7.6:1 compression ratio, the 270 produced 183 hp. In the Dodge Royal, the “Super Red Ram” used a four-barrel carburetor and produced 193 hp.
The 315 Dodge Red Ram Hemi V8 D-500-1 Race Engine Package
For 1956, Dodge offered an optional high-performance D-500 version of the 315 CID (5.2 L) Hemi engine with a four-barrel carburetor. In addition, a “race only” package called the D-500-1 was available through special order with a high flow aluminum intake manifold that carried a pair of four-barrel carburetors. The D-500-1 engine utilized the same Hemi cylinders heads as the base D-500 model.
Dodge released a 325 CID (5.3 L) engine for 1957. The base engine came with non-Hemi ‘KDS’ heads while a higher performance 325 was offered with Hemi heads as the ‘KD-500’. Again there was the option of a ‘KD-500-1’ package with dual four barrel carburetors. At this point, all engines carried hydraulic camshafts even though the Hemi valve covers continued to feature dimples to clear the mechanical adjusters.
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