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Got a HEMI? A Look Under the Hood at the Legendary Performance Icon

The insatiable need for speed and power has defined the automotive landscape since the late 1890s and early 1900s when we replaced the trusty steed and its carriage with the automobile. This need eventually paved the way for legendary engines like the HEMI found at Ram dealerships throughout the country today. But what makes the HEMI engine a prime example of our innate need to go faster and travel farther? Why is the HEMI considered a performance icon?

The History Behind the HEMI

HEMI is synonymous with performance, with many likening the name to former Dodge commercials asking, “That thing got a HEMI?” However, the HEMI is much older than most people imagine, proving our need for speed isn’t modern. Instead, it’s defined every aspect of our landscape since we first discovered the freedom of traveling on four wheels.

The first account of a HEMI engine is from 1905 when Alfred and Victor Goldschmidt developed a HEMI engine to build the Premier racecar for their business, the Belgium Pipe Company. While the engine was powerful enough to win the race, it was disqualified from future races because of its excessive weight. Even so, the HEMI’s capability immediately garnered acclaim, inspiring others to redesign the engine to remedy its imposing weight. Within two years, a feasible design was born when Fiat debuted a 130-horsepower HEMI engine that gave the Grand Prix racecar an advantage over French rivals. The victory was sweet, albeit short-lived.

While the HEMI was potent, it was expensive to build and forced many automakers to delay their projects. It wasn’t until the dawn of World War II that the HEMI finally returned to the spotlight when Chrysler lent its efforts to the war. Engineers recognized the need for more capable engines to accommodate military vehicles and aircraft, which set the perfect stage for reintroducing the HEMI. Chrysler engineers successfully answered the demand, relying on a V-12 HEMI engine to power the M47 Patton tank and a V-16 HEMI engine to deliver 2,500 hp to the P-47 Republic Thunderbolt fighter plane.

The Reason Behind Its Power

While the history of the HEMI engine is expansive, there’s still the question of what makes it a performance icon. How does it differentiate itself in a realm of capable powertrains? It’s all in the name.

A HEMI distinguishes itself by its hemispherical combustion chamber, a stark contrast to the traditional flathead engine used on most models built until the 1950s. In a flathead engine, the valves are positioned in the engine block and open in the combustion chamber adjacent to the piston. While the simplified design works, the excessive surface area relative to the size of the combustion chamber causes a dramatic loss in heat. Think of it like using a single match to heat your living room. In this case, the pressure in the cylinder is dramatically reduced and limits the engine’s peak performance.

The HEMI’s hemispherical combustion chamber solves this issue because of its unique design. The dome-shaped heads feature a spark plug at the top and valves on either side of the combustion chamber. The position of the spark plug shortens the distance the air-fuel mixture travels before combustion occurs. Likewise, the layout allows for larger valves to increase airflow. With compression optimized, airflow increased, and the surface area reduced, the HEMI creates the perfect setup by burning fuel more efficiently and enhancing the combustion process to deliver significantly more power.

The Engines in the HEMI Legacy

Although Chrysler was already established as an automotive pioneer, the automaker sealed its fate in the early 1950s when it recognized the appeal a HEMI-powered vehicle would have to civilians. Chrysler took everything it learned in designing the HEMI for military tanks and aircraft and applied it to its commercial fleet. The first-generation HEMI officially debuted in 1951 as the FirePower 331. As the first overhead-valve V8 engine in the Chrysler fleet, the FirePower made headlines for producing 180 hp, a notable increase over the 40-horsepower engines that caused most people to sigh with appreciation.

Despite the success of the FirePower, Chrysler continued fine tuning the HEMI’s design and looking for more ways to increase its power output. The late 1950s saw the introduction of the 293 HEMI, but it wasn’t until 1964 that the HEMI truly became synonymous with performance. The 426 cubic-inch HEMI was destined for NASCAR as an extra big-block engine sitting under the hood of the Plymouth Belvedere. The HEMI fulfilled its destiny, with the Belvedere taking the top three spots at the 1964 Daytona 500, leaving no question that the HEMI was in an entirely different realm of power.

The HEMI’s incredible output and exceptional performance at the Daytona 500 caused widespread pushback. Rivals argued Chrysler had an unfair advantage, ultimately leading to new regulations that banned the extra big block. Chrysler responded by retuning the HEMI, making it street-legal with a lower compression ratio and milder components. Even then, it produced 425 hp and found its way under the hood of icons like the Plymouth Barracuda SS, Dodge Challenger, and Dodge Charger.

These street-legal HEMI models solidified the HEMI’s reputation in the industry, ultimately earning them the nickname “Elephant HEMI” and marking Chrysler’s steps to trademark the name. At the same time, the HEMI showcased Chrysler’s ingenuity and gave the automaker the green light to return to the NASCAR circuit. By 1971, HEMI was synonymous with performance, redefining the muscle car segment and making 426 HEMI-powered models the ultimate collectible.

The HEMI as We Know It Today

From the 1950s to the 1970s, the HEMI was limited to high-performance cars and those destined for the track. However, Chrysler changed that in 2003 when it introduced the third-generation HEMI, making it more practical, affordable, and accessible for everyone. These characteristics debuted on the 2003 Ram 1500, 2500, and 3500, powered by the 5.7L V8 engine featuring two spark plugs and advanced fuel injection to improve efficiency.

Eventually, the engine was modified with variable valve timing, new cylinder heads, and redesigned intake manifolds that pushed the HEMI’s horsepower output to nearly 400 hp. Fortunately, this sheer capability wasn’t limited to those with deep enough pockets to invest in a performance car. Instead, it was readily available in everything from Ram trucks and the award-winning Jeep Grand Cherokee to the Dodge Challenger, Charger, and Durango.

The HEMI’s evolution has continued since the new millennium, with Chrysler introducing more power and capability. We see this in the 425-hp 6.1L HEMI designed for the SRT8 lineup and in powerplants like the 6.4L HEMI Apache. The Apache builds on the 5.7L HEMI, producing up to 525 hp without compromising efficiency. The combination is incredible, making models like the Dodge Charger, Jeep Grand Cherokee, and Ram Heavy Duty enigmas in an industry where performance often comes at the cost of efficiency.

The HEMI’s latest chapter introduces drivers to the 6.2L Hellcat, a powerhouse rated at over 700 hp and 650 lb-ft of torque on models like the Dodge Challenger SRT Hellcat. The supercharged powerhouse is named after the F6F Hellcat fighter plane used in World War II, a tribute to the HEMI’s incredible role in American history and Chrysler’s ingenuity in developing the HEMI engine to aid in the war. Today, the Hellcat Redeye builds on that reputation, with the high-output version redefining HEMI-like performance by churning out nearly 800 hp and over 700 lb-ft of torque for jaw-dropping power.

That Thing Got a HEMI?

Dodge introduced us to the HEMI with ad campaigns that begged the question, “That thing got a HEMI?” Looking back, the automaker’s marketing plan was a stroke of genius because it forever tied the performance icon to the American automotive pioneer. Today, there’s no doubt the HEMI plays an integral role in the Dodge, Ram, Chrysler, and Jeep lineups.

While the HEMI is linked to these brands, it’s also incredibly significant as a performance icon because it proves Chrysler’s success at thinking outside the box. Chrysler may not have been the first to develop the hemispherical engine layout, but it was the first to make the design accessible to the masses. The HEMI’s role in World War II to its impact on the American landscape as we experience it today is undeniable, satiating our need for speed mile after mile and giving us more reasons to ask the question that Dodge encouraged decades ago.