It’s April 26 (4/26) or as us Mopar fans affectionately call it, HEMI Day! Of course, the reference comes from the legendary 426 cubic inch HEMI V8 built from 1964 through the 1971 model year. Dubbed the “Elephant” HEMI due to its huge size and power output.

Gen I Hemi 1951-1958

The Chrysler Corporation originally started using the hemispherical cylinder head design in 1951, although they weren’t called Hemis at the time. Each division had a different name for their new engine families featuring the hemispherical combustion chamber. Chrysler called theirs the FirePower and it was available in 331, 354, and 392 cubic inch variants between 1951 and 1959. DeSoto called theirs the Fire Dome, originally introduced in 1952 as a 276 cubic inch engine and was subsequently enlarged to 291, 330, 341, and 345 cubic inches throughout its production period.

Dodge had two names for their hemispherical engine family, Red Ram for passenger car variants and PowerDome for Dodge Trucks. A 241 cubic-inch version was introduced in 1953, which was replaced in 1955 by a 270 cubic-inch rendition. In 1956 Dodge again went bigger, increasing the engine size to 315 cubic inches by going to a longer stroke and a taller raised deck block. This engine went away from the hemispherical head, but an optional “hotter” version of the engine had a hemispherical combustion chamber, larger valves, and a four-barrel carb.  In 1957 Dodge released a new 325 cubic-inch engine, again the standard version had polyspheric cylinder heads, while the high-performance offering came with hemispherical heads.

The Gen II Hemi 1964-1971 The “Elephant”

Six years after production ended on the first generation Hemi engines, the Chrysler Corporation introduced the legendary 426 cubic inch Hemi V8. For the first time officially wearing the Hemi name this massive engine had a 10.72 inch deck height and a 4.8 inch bore spacing making it the largest engine in racing at the time of introduction.  Originally produced for Chryslers Nascar program it was used it a racing version of the Plymouth Belvidere and was not available to the general buying public. The 426 was banned from the 1965 Nascar season as it was not sold to the general public. This was remedied later in 1965 as Chrysler shoe-horned the engine into the Dodge Dart and Plymouth Fury. Later on in 1965 a version of the Dodge Coronet was introduced with aluminum fenders and bumpers, with the large cube engine under the hood for drag racing. 

In 1966 the Street Hemi was introduced and was available in a wide range of Chrysler Corporation vehicles again legitimizing its use in the Nascar circuit and putting Dodge on the top of the muscle car map. The Street Hemi differed from the race Hemi by having a lower compression ratio, more streetable camshaft, and more. Even so the Street Hemi was rated at 425 SAE Gross horsepower and 490lb-ft of torque. Just 11,000 426 Hemis were produced for the buying public between 1966-1971.

Gen III Hemi 2003-Current

Fast forward to 2003, an all-new Ram 1500 was introduced just a year earlier and a new Ram Heavy Duty lineup was debuting. The old 5.2 and 5.9 Magnum engines were no longer competitive with newer offerings from Ford and General Motors, while the more modern 4.7 SOHC Magnum V8 was relatively expensive to produce and still outpowered by its rivals. Dodge needed a new powertrain under the hood of their new trucks and they did not disappoint. Again rebirthing the Hemi name with a new 5.7 liter (345 cubic inch) V8 with two spark plugs per cylinder, a hemispherical combustion chamber, and all the latest technologies. At launch, this engine developed 345 horsepower and 375lb-ft of torque, outpowering the outgoing 5.9 liter Magnum V8 by 100 horsepower and 40lb-ft of torque, while being more fuel efficient.

The 5.7 was a huge hit and has since been available in a variety of products and has been refined over the years with cylinder deactivation, variable valve timing, and a power increase. Even more important to enthusiasts though was the 5.7 opening the door to other variants such as the 6.1 Hemi, 6.4 (392) Hemi, the legendary 6.2-liter Hellcat supercharged V8 along with the Demon and Redeye models, and who could forget the supercharged 426 cubic inch Hellephant crate Hemi. 

The Hemi has once again put Dodge on top of the muscle car game, gaining the brand even more enthusiasts both young and old that like to modify their vehicles, take them to car shows, and participate in racing activities. I have enjoyed all the Hemi-powered vehicles that I’ve owned (5.7 Hemi, 6.4 Hemi, and Hellcat), and have had a lot of fun and made a lot of friends along the way through mutual interests. That is the point of the video above, having fun with your friends in your Hemi-powered rides. 

What is your best memory with a Hemi-powered vehicle? Let us know in the comments down below.