HAPPY 4/26 HEMI® Day!

Celebrating The Legendary HEMI Engine...

April 26th holds a special significance for Mopar fans, who call it HEMI® Day. This day celebrates the legendary 7.0-liter (426 cubic-inch) HEMI V8 engine, manufactured between 1964 and 1971. This engine was nicknamed the “Elephant” due to its massive size and impressive power output, and it has left an incredible mark on the automotive industry. 

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Despite being out of production for years, its legacy continues influencing modern HEMI engines, making it a popular choice for muscle car enthusiasts.

GEN I HEMI (1951 to 1958) –

The hemispherical cylinder head design was first used by the Chrysler Corporation in 1951, though it was not referred to as a HEMI at that time.

Each division had its name for its newly designed engine family featuring the hemispherical combustion chamber. Chrysler named theirs the FirePower, and it was available in 331, 354, and 392 cubic-inch variants from 1951 to 1959.

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DeSoto called their version the Fire Dome, initially introduced in 1952 as a 276 cubic inch engine, which was later increased to 291, 330, 341, and 345 cubic inches during its production period.

Meanwhile, Dodge had two names for their hemispherical engine family; Red Ram for passenger car variants and PowerDome for Dodge Trucks. First, they launched a 241 cubic-inch version in 1953, replaced by a 270 cubic-inch model in 1955. Dodge later increased the engine size to 315 cubic inches in 1956, which moved away from the hemispherical head design. Still, an optional “hotter” engine version had a hemispherical combustion chamber, larger valves, and a four-barrel carb. Finally, in 1957, Dodge introduced a new 325 cubic-inch engine, with the standard version sporting poly-spheric cylinder heads, while the high-performance offering came with hemispherical domes.

GEN II HEMI (1964 to 1971) –

The Chrysler Corporation introduced the famous 426 HEMI V8 engine six years after discontinuing the production of the first generation HEMI engines. This massive engine featured a 10.72-inch deck height and a 4.8-inch bore spacing, making it the giant machine in racing at its introduction and officially bearing the HEMI name.

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Initially designed for Chrysler’s NASCAR program, the engine was exclusively used in a racing version of the Plymouth Belvedere and was not available for public purchase. However, when it was not sold to the general public, it was banned from the 1965 NASCAR season. To remedy this, Chrysler fitted the engine into the Dodge Dart and Plymouth Fury later that year. Additionally, in 1965, a version of the Dodge Coronet was introduced with aluminum fenders and bumpers, featuring a large engine under the hood for drag racing.

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In 1966, the Street HEMI was unveiled and made available in a wide range of Chrysler Corporation vehicles, legitimizing its use in the NASCAR circuit and cementing Dodge’s position at the top of the muscle car hierarchy. The Street HEMI had a lower compression ratio, a more street-able camshaft, and other differences that distinguished it from the racing HEMI. Nevertheless, it was rated at 425 SAE gross horsepower and 490 lb. – ft. of torque. Only 11,000 units of the 426 HEMI were produced for public purchase between 1966 and 1971.

Gen III HEMI (2003 to Present) –

In 2003, Dodge introduced an all-new Ram 1500 and a new Ram Heavy Duty lineup, as the old MAGNUM engines were no longer competitive with newer offerings from Ford and General Motors (GM). Dodge needed a new powertrain for their trucks, and they did not disappoint by introducing the new 5.7-liter (345 cubic-inch) HEMI V8 engine. The HEMI name was reborn with this engine, featuring two spark plugs per cylinder, a hemispherical combustion chamber, and the latest technologies. At launch, the engine produced 345 horsepower and 375 lb.-ft. of torque, outpacing the outgoing 5.9-liter (360 cubic-inch) MAGNUM V8 by 100 horsepower and 40 lb.-ft. of torque while also being more fuel-efficient.

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The 5.7-liter HEMI was a huge success and has since been available in various products, with several improvements such as cylinder deactivation, variable valve timing, and power increase. Additionally, the 5.7-liter HEMI (Eagle) opened the door to other variants such as the 6.1-liter HEMI (SRT), 6.4-liter (392 cubic-inch) HEMI (Apache), the legendary supercharged 6.2-liter HEMI HELLCAT V8, as well as the Demon and Redeye variants, and the supercharged 7.0-liter (426 cubic-inch) HELLEPHANT crate HEMI. The HEMI has once again made Dodge the top contender in the muscle car game, gaining more enthusiasts who like to modify their vehicles, attend car shows, and participate in racing activities. 

Video Source: MotorTrend

Robert S. Miller

Robert S. Miller is a diehard Mopar enthusiast who lives and breathes all that is Mopar. The Michigander is not only the Editor for MoparInsiders.com, 5thGenRams.com, and HDRams.com but an automotive photographer. He is an avid fan of offshore powerboat racing, which he travels the country to take part in.

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April 26 is known as HEMI® day to those in the automotive world. The reference comes from the 426-cubic-inch HEMI V8 engine that was introduced in 1964 and was available through the 1971 model year. It was nicknamed “Elephant” because of its massive size and impressive output.

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