What Are the Advantages of Hemi Engines? 

If you’re into muscle cars, you might have seen or heard about Hemi engines in forums, videos, or conversations. If you’re unfamiliar with the term, don’t worry. In this article, we’re going to tackle everything you need to know about Hemi engines.

What’s a Hemi?

Hemi is a term that means an engine type with a hemispherical cylinder head design. Hemi engines have been trademarked by Chrysler since the ’60s. This is why Hemis are typically inline six-cylinder and V8 engines made by Chrysler. However, the design has also been previously utilized by other brands.

A Hemi engine has cylinders with domed heads rather than flat heads. The Hemi engine’s design can provide more power compared to a conventional engine because it allows higher compression ratios and facilitates better air-fuel mixtures inside the cylinder. This allows the engine to ignite all the fuel inside the cylinder, resulting in more heat and more energy.

What Does a Hemi Engine Offer?

A Hemi engine features a highly efficient combustion chamber, making it far more powerful than other past engine types, like flathead engines. Aside from producing more heat, Hemi engines also have a dome-shaped cylinder head with two large, slanted valves. Their sheer size allows for better airflow.

The domed cylinder design increases the volume of air-fuel mixture that can be burned. At the same time, it lessens the surface area of the cylinder head. Since the cylinder head has less surface area, it absorbs less heat, letting the combustion chamber retain more heat. Preserving heat inside the combustion chamber is important because higher temperatures in the combustion chamber create more pressure during ignition.

Disadvantages of Hemi Engines

The biggest downsides of having a Hemi engine are its limiting valve configuration, high upfront and maintenance costs, complicated design, and heavy/unwieldy nature.

Few Valves Per Cylinder

One disadvantage that comes with Hemi engines is that they only have two valves per cylinder, which severely limits their airflow.

Most modern vehicles have four-valve designs, which means Hemi engines aren’t capable of breathing as easily.

Hemi engines can get hot faster and stay hot for longer because they aren’t capable of cooling themselves down efficiently.

Expensive to Make and Maintain

Hemi engines are more expensive to produce than most engine types. On top of that, they’re also incredibly costly to maintain. Expect to spend a lot of money owning and maintaining any vehicle with a Hemi engine.

Complex Designs

Despite the many benefits Hemi engines have to offer, they can be inconvenient in certain ways. One of their biggest problems is how complex they are. This makes them difficult to clean, service, and maintain. Unsurprisingly, this also makes labor costs for working on them very high.

Unwieldy

Another downside to Hemi engines is how big and heavy they are. It can take a lot of effort to remove them from a vehicle, making them difficult to work on when it’s time for repairs. Their tremendous weight also negatively affects handling and fuel efficiency.

Three Generations of Hemi Engines

The first vehicle with a Hemi engine was made by a company in Michigan called Welch in 1904. Afterward, many car manufacturers like Peugeot, Alfa Romeo, and Daimler started making their own Hemi engines. Chrysler first started using Hemi engines when it was making fighter planes in World War II. It decided to integrate the technology into its road cars after the war. The Hemi has gone through several evolutions throughout Chrysler’s history:

First Generation

In 1950, Chrysler introduced the first generation of Hemi engines. The engine was called the FirePower engine and it was standard in the 1951 Chrysler New Yorker and Imperial, and an option for the Saratoga. The powerful 392 engine from this generation was popular among drag racers. It became the standard and preferred engine for drag racers until the ’70s.

Second Generation

The second-generation 350-horsepower Hemi engine called the 426 was unveiled in 1964. This engine was the first time the Hemi term was used. The 426 engine was nicknamed the Elephant engine because it was extremely powerful and very large. Chrysler built this engine specifically for the National Association for Stock Car Auto Racing (NASCAR), and it made its NASCAR debut under the hood of a 1964 Plymouth Belvedere. However, NASCAR outlawed the car by prescribing that manufacturers must also produce the engine for their consumer vehicles. Shortly after, a tuned-down version of the 426 was integrated into Chrysler consumer vehicles.

The Hemi name as we know it today was born during this time period, with Dodge, Chrysler, and Plymouth all choosing Hemi engines for their performance cars.

Third Generation

Hemi engines went on a hiatus from the ’80s up until the early 2000s. They were reintroduced in 2003 with the 5.7-liter Hemi in various Dodge RAM pickups. The design was also changed so that the engine could comply with modern emissions standards. Third-generation Hemi engines now have two spark plugs instead of one. Currently, several vehicles made by Stellantis (formerly Fiat Chrysler) have the Hemi name. However, not all Stellantis vehicles are equipped with engines that have hemispherical cylinders. Only several models like the Challenger, Charger, Grand Cherokee, and Durango have retained the true hemispherical cylinder head design.

Why Do People Love Hemi Engines?

Much of what makes a Hemi engine special is the shape of its cylinders and cylinder head. You can certainly appreciate its performance if you’re in the driver’s seat, or if you’re a bystander watching someone race a car equipped with a Hemi engine on a drag strip. Aside from these scenarios, appreciating something that’s hidden under the hood is difficult. Now that Hemi engines are slowly being phased out, they might become an outdated relic from the past. You no longer need large displacement Hemi engines to produce a lot of power because smaller engines with turbochargers can produce the same amount of power more efficiently. This begs the question: why do people still hold the Hemi name in high regard?

The engine’s sound is one of the main appeals of any performance vehicle. The characteristic deep rumble from the Hemi engine isn’t only unique, it can also be emotionally evocative.

For some, the term Hemi can also mean a car that has a big, powerful engine. Setting aside the engine’s technical advantages, the Hemi engine’s appeal is due in part to its heritage. Muscle car enthusiasts continue to hold it in high regard because of its history of being on American drag strips and in NASCAR. The engine can mean a lot to American car enthusiasts, who see it as a status symbol.

Why Don’t All Vehicles Use a Hemi Design?

Hemi engines are designed to produce large amounts of power. However, they weren’t designed to be fuel-efficient. The domed piston heads inside Hemi engines can be substantially heavier than the traditional piston. Since the crankshaft needs to pull the piston down at the top of its stroke, a heavier piston means this process will require more energy. The energy used to reverse the piston’s momentum is energy lost.

However, Hemi engines aren’t the cutting edge of engine design anymore. Many modern sports cars and performance vehicles use turbocharged engines because they can produce the same amount of power while being able to comply with strict government environmental and efficiency standards. That said, Hemi engines will always have a place in the hearts of American muscle car enthusiasts because of their trademark sound and heritage.