Chrysler Hemi engines, better known under the Hemi brand name, are a series of V-shaped power units with eight cylinders using a hemispherical combustion chamber.
The hemispherical (i.e. ball-shaped) combustion chamber allows two valves per cylinder to be angled, facing each other. This type of arrangement leaves significant space in the combustion chamber for the use of large valves, which in turn are capable of increasing the flow area of the valve slot. From the material we know that by increasing the cross-section of the valve slot, both the purge and the filling of the cylinders are improved, giving stable engine operation at high speeds. In theory, these features will undoubtedly have a positive effect on increasing the power output in general, but in practice, losses in efficiency are not excluded in the form of an incompletely burnt air-fuel mixture directly at the exhaust valves. Plus, due to their lack of hardening, hemispherical combustion chambers are more sensitive to the octane number of the fuel.
FirePower OHV V8
Chrysler is applying its military experience with the hemispherical combustion chamber to build the first overhead valve powertrain. The engine was released in 1950 under the name “FirePower”, had a useful volume of 5.4 liters in 8 cylinders with a V-arrangement and was rated at 180 hp. (134 kW).
1964 saw the birth of the most recognizable engine in automotive history, the 7.0 liter Hemi (426 cubic inches). At that time, being the largest and most efficient power units for passenger cars in general and NASCAR races in particular. The 426th HEMI on the dynamometer showed a result of 433.5 horsepower and 640 Nm of torque, but only 425 forces flaunted in the passport data. Understating the actual technical characteristics was a well-known practice of American car manufacturers, sometimes “mistakes” reached up to 100-150 hp. in favor of the owner. This allowed motorists to significantly save on the insurance policy, and racers to have a small “head start” in front of rivals. Ultimately, only 11,000 of these engines were produced for sale, all due to increased requirements for the design and dimensions of the engine compartment,
The 426th Hemi was optionally installed on the Dodge Coronet (1966-1970), Dodge Charger (1966-1971), Dodge Dart (1968), Plymouth Barracuda (1968-1971), Plymouth Road Runner , etc.
The 5.7 L Hemi was released for the 2003 model year for the Dodge Ram 1500, 2500, and 3500 pickups, replacing the 5.9 L Magnum engine. A year later, Chrysler made this unit available for all 2004 Dodge Ram, Dodge Durango, 2005 Chrysler 300C, Dodge Magnum R / T, 2005 Jeep Grand Cherokee, 2006 Dodge Charger R / T and 2009 Dodge Challenger R / T.
With a basic setting of 5.7 L, the Hemi produced 345 hp. (257 kW) at a maximum torque of 540 Nm. Thanks to all sorts of variations, the performance of this unit could insignificantly (+/- 20 hp) fluctuate in one direction or another.
Chrysler is soon revising its previous powertrain with larger combustion chambers and a focus on cooling. The cast aluminum intake manifold is now pre-tuned for high revs. And a forged crankshaft, lightweight pistons, and reinforced connecting rods added durability to the new engine. 6.1 HEMI was limited to the SRT subsidiary for the Chrysler 300C SRT-8 (2005-2010), Dodge Charger SRT-8 (2006-2010), Jeep Grand Cherokee SRT-8 (2006-2010) and Dodge Challenger SRT-8 (2008 -2010).
Chrysler sets a new record for high-performance V-8 units with the release of the 6.4 liter Hemi in 2005. Power 6.4 HEMI is rated at 532 horsepower (391 kW) at 691 Nm of torque. Its base is an iron cylinder block with aluminum alloy pistons. This engine has been available for mass production since 2007 under the name “392 Hemi”. Similarly to its “brothers”, the 392nd Hemi is subjected to certain factory upgrades and settings for different models, modifications, as well as all kinds of “special versions” of cars. Chrysler LLC is currently using this engine for its highest performing vehicles – the SRT8 Dodge Challenger, SRT8 Dodge Charger, Chrysler 300C and Jeep Grand Cherokee . And what the next power unit will be, I hope we will soon see!
– poor environmental performance
– sensitivity to the octane number of the fuel
+ acceleration throughout the entire rev range
+ reliability and durability
HEMI engine history
In the early days of the automobile, no one paid much attention to its performance. Ordinary cars were technological marvels on dirt roads that hadn’t been built for anything but horses and their cars. As the auto industry matured, roads were improved and then paved, and performance became an important tool for car sales.
As early as 1926, the third year for the Chrysler brand, performance was tied directly to the names of the cars. The four-cylinder 50 series model was capable of 50 miles per hour and the six-cylinder series 60, 60 miles per hour. The Imperial 80 could reach a top speed of 80 miles per hour, assuming you could find a long and fairly smooth road to reach such inconceivable speeds. While few can dispute the fact that Ford’s introduction of the Flathead V-8 in 1932 had a profound impact on the birth of hot rodding, it wasn’t until 1951 that Chrysler took a big step toward performance and forever changed the world of racing.
In a radical departure from the common shaft raised valve design, Chrysler introduced the new 331-CI Fire Power V-8. The intake and exhaust valves were mounted on separate shafts, the spark plugs were located in the center of the combustion chamber in a dome (or hemispherical) shape. Power was just 180 horsepower at 4000 rpm with a modest 7.5: 1 compression ratio. Although by then it was designed to be more efficient in passenger cars, this was the start of great things, and the Hemi was born.
Once Chrysler engineers were “pinched” by the new Hemi, more and more horsepower was drawn from it. When the 1955 models debuted, the Hemi 331 was now offering 250 horsepower in passenger cars. On February 10, midway through the model year, Chrysler dropped a bombshell on the rest of the auto industry. The Chrysler 300C was introduced, and its name was again attached to the 331 Hemi’s 300 horsepower performance. It was the industry’s first 300 horsepower engine. The 1955 300C was probably the first Muscle Car, and with it began the “Horsepower war” era in Detroit, which would last for almost two decades. The Hemi was expanded to 354 cubic inches and 340 horsepower in 1956, and would grow to 392 cubic inches to reach 390 horsepower by 1957.
The Hemi may have ceased production after 1958, but this one was far from going. Don Garlits, then a little-known dragster racer from Florida, had bought a 1956 331 Hemi from a 1954 Chrysler for scrap. He installed the engine in his Slingshot Dragster, and the long and legendary history of the Hemi had begun. These days this story is written like all Top Fuel and Funny Car engines based on the Chrysler Hemi.
In the early 1960s, America’s loves was racing fever. Stock car racing, which had its roots in the south, became popular across the country. On the opposite side of the continent, California had given birth to the drag race. In the early 1960s, almost every metropolitan area in the country had at least one drag track nearby. The automakers were in obvious competition to boast of their victories, and while the Chrysler cars were more than sustained in the battle, there was still no clear winner!
The 1964 racing season debuted in Florida with the Daytona 500. Dodge and Plymouth had a new engine, the Hemi 426 “Crate Motor,” which was available only to Stock racers at the time. Based on the successful 1962-1964 Max Wedge design, the new Hemi featured a nearly identical valve train arrangement to the Early Hemi, but now used more modern casting techniques to eliminate weight, such as production costs. The new Hemi engine had been designed solely for NASCAR racing, and Richard Petty won the 1964 Daytona 500 in his Petty Blue # 43 Plymouth station wagon. A drag version of the Hemi engine soon followed and was factory installed available later in the year as a performance change from the Max Wedge, but it was a serious racing-only package and was not appropriate for utility transport use.
The new Hemi was an immediate hit on drag tracks just like (and still is) in Stock auto racing. The mopar drag racers had a first love / hate relationship with the Hemi until they learned how to fit them properly. Gifted, the Hemi was the car / engine combination to seriously hit the competition. But the muscle car frenzy was pulled from the streets of America and Chrysler was losing a lot of sales – a temporary situation that was overcome in 1966 with the introduction of the Street Hemi. The new engine was available only on the Plymouth Belvedere and Dodge Coronet models, along with the newly introduced Dodge Charger.
The rest, as they say, is history. Until its demise after the 1971 model year, the 426 Street Hemi, which was more than just a mismatched racing engine, was the most impressive production engine engine of any manufacturer. Had the Hemi survived the year 1972, Tom Hoover (Hemi’s father) has said that it is almost a given that he could have had the dual four-barrel carb for a six-barrel setup. It was also possible that the valvetrain had eventually mutated a prototype rolled design, but it never got that far.
The Hemi died a peaceful death – a combination of factors can be found on his death certificate. Demand fell sharply (driven in large part by rising fuel prices and pressure from the insurance industry), the high cost of producing fuel, and increasingly stringent emission quality standards. Is the Hemi really dead! Take a look at today’s passenger car engines and see how the spark plugs enter the combustion chambers and the arrangement of their valves. Efficiency comes in many forms and the efficiency of the Hemi’s design lives on long after its demise. There is no word in the English language to adequately describe or pay tribute to the Hemi engine.
The Hemi engine is one of those rare inventions that earns a special place in American automobile history. Although Chrysler did not invent the Hemi combustion chamber, they perfected the Hemi and used it to its highest potential. The Hemi combustion chamber first appeared on 20th century Welch passenger cars, it also honored the mystical Dusenberg and Stutz brands. Chrysler first became involved with the Hemi during WWII with experimental Hemi-style engines designed for tanks and aircraft. Between 1941 and 1945, the Detroit Chrysler factory produced 22,234 tanks and the Chrysler’s Chicago plant produced Wright Cyclone radial engines for the B-29 area fortress.
Chrysler first introduced the Hemi in a production car in 1951. It displaced 331 cubic inches and produced 180 horsepower. The 1950s were a time when much of the technology developed during World War II was put to use in the design and manufacture of consumer products. This was a time of consumerism. There was a new enthusiasm for cars, houses and other goods. The new Hemi engine fitted perfectly into the new Chrysler designs of the 1950s. The timing of the new engine was also important because it kept Chrysler on par with Cadillac and Oldsmobile, both of which launched new overhead valve engines for their car lines.
During this time, Americans began to view cars as more than just a source of transportation. Automotive enthusiast magazines were beginning to appear on newsstands where connoisseurs could read road tests comparing their favorite models. Car races of all kinds were set up and fans were able to watch the cars go head-to-head on the track or in an economic race. The only downside to the Hemi was the heavy vehicle that was loaded with propulsion. In 1957, the AMA asked automakers not to encourage racing. While Chrysler enjoyed the successes of racing, the advantage of publicity was not provided at that time.
The cost of producing the Hemi engine and the evolution in wedge cylinder design was no longer an available option for Chrysler’s passenger car choice. The Hemi was expensive to build and much heavier than any of the new wedge designs. Its true potential was also not exploited by the use of the passenger car. When the first Hemi engines were discontinued at the end of the 1958 model year, it quietly disappeared as another chapter in the evolution of the automobile.
Both NASCAR and NHRA wanted to support the development of new engines, but they also wanted to see those engines available to all competitors, not just a select few. The rules were written to ensure that the engines being competed were available, in some form, to the average car buyer. To fulfill this, Chrysler introduced the street Hemi in 1966. Unconsciously, Chrysler wrote another chapter in automotive history by providing the customer with a racing engine in a street version. Ford, Chevy and Pontiac all produced legendary muscle cars in the 1960s and early 1970s, but none had the lasting impact of the street Hemi. The engineering of the street Hemi package was superb: there were no weak points.
5.7 hemi issues – Learn about the common issues that arise with the 5.7 hemi engine in Dodge vehicles and how they can affect driving.
Dmitry Petrov is an engineer who specializes in materials science, and has a deep passion for all things related to automotive technology. He is a true motorhead at heart, and spends much of his free time tinkering with engines and studying vehicular dynamics.