The Dodge Hemi V8 is an iconic part of the American auto giant’s history that lives on today. Here are the best details on the modern Hemi engine.
Since the early 2000s, the Dodge Hemi engine design has been a staple of the brand’s lineup, from Ram trucks to their iconically retro-styled muscle cars, the Dodge Charger and Dodge Challenger.
However, the lineage of the Hemi engine goes much further back than the early 2000s. In fact, the Hemi engines we have today are known as the third-generation Hemi family.
The history of the Hemi engine actually dives far beyond just Dodge and is traceable all the way back to the 1950s. Let’s take a brief look at the history of the lineup of Hemi engines and what is available in today’s new and used market as far as these iconic V8s go.
First, though, the most commonly asked question about these engines is regarding what makes a Hemi engine special.
What is a Hemi Engine?
Hemi is shorthand for hemispherical. This is in reference to the perfectly symmetrical dome-shaped combustion chambers in the engine’s cylinder heads. With spark plugs centered in the top of the dome, flame travel and burn distance is shortened and equalized to all edges of the combustion chamber, making for more efficient lighting of the air/fuel mixture in the chamber.
Get more details on the Hemi in Engineering Explained‘s YouTube clip, above.
Other than the hemispherical combustion chamber, Hemi engines are a standard pushrod V8 engine.
History of the Hemi
The first production variant of the Hemi engine was not developed for Dodge vehicles. In fact, it wasn’t even called a Hemi. But it does use the hemispherical combustion chamber design.
It is known as the Chrysler Firepower V8 and came standard in the Chrylser Imperial and New Yorker as well as some DeSoto-branded vehicles. The firepower V8 was retired after 1958.
The hemispherical cylinder-head design made a triumphant return with the 426 cubic-inch Hemi engine. This engine is perhaps the most iconic in Hemi history as it was developed for NASCAR use and made its way into production vehicles.
The 426 Hemi V8 was found in all sorts of cars from Dodge and Plymouth. This list includes but is not limited to the Barracuda, Charger, Coronet, Satellite, GTX, Charger Dayton, and the iconic Plymouth Super Bird.
The 426 Hemi engine remained in production until 1971, when it was discontinued.
The Hemi nomenclature would remain unused until its reintroduction with the 2003 Dodge Ram pickup truck in the form of a 5.7-liter V8. Like its predecessors, it uses hemispherical combustion chambers.
However, the modern Hemi uses two spark plugs per cylinder to increase ignition efficiency further.
Furthermore, the addition of modern engine technologies like fuel injection and coil-on-plug distributor-less ignition make the Hemi mightier than ever.
Since the re-introduction of the Hemi in 2003, power and performance figures have only increased. Let’s take a look at some of the performance figures of the almighty modern Hemi engines.
Dodge Hemi 5.7 V8
Like their ancestors, all modern Hemi engines use standard pushrod V8 construction. There are a few different variants, and we’re going to start with the one that brought back the Hemi name, the 5.7. Here are its specifications.
The 5.7 Hemi uses a cast-iron engine block with aluminum cylinder heads. It has a bore of 99.49 millimeters (3.917 inches) and a stroke of 90.88 millimeters (3.578 inches). It uses two valves per cylinder and standard multiport fuel injection.
From 2003 to 2008, the 5.7 Hemi V8 used a 9.6 to 1 compression ratio. Horsepower varied between 340 and 345 horsepower depending on what vehicle it was found in. Torque output is 375 lb.-ft.
In 2009, changes were made to the 5.7 to increase power and efficiency. These changes included more efficient cylinder heads and increasing the compression ratio to 10.5 to 1. Power again varies from 383 to 395 horsepower depending on which model and year it was in. Torque numbers saw an increase to up to 410 lb.-ft.
Additionally, some Hemi 5.7 V8s are equipped with cylinder deactivation technology to increase fuel economy. Though, heavy-duty trucks and cars with manual transmissions do not have this feature on their 5.7 Hemi engines.
With the 2019 Ram 1500, a mild-hybrid variant of the 5.7 Hemi V8 became available, though it is exclusive to the Ram 1500. It is known as the eTorque Mild Hybrid System.
Instead of an electric motor driving the wheels, a 48-volt electric motor effectively replaces the alternator. Under deceleration and braking conditions, the eTorque motor generates power and charges an onboard battery pack. It can also add additional bursts of torque up to 130 lb.-ft.
Hemi 6.1-liter V8
Like the 5.7, the 6.1-liter Hemi uses standard pushrod V8 construction. This engine is found in SRT8 vehicles and has a bit more punch to it than the 5.7, as you’d find in R/T models and Ram trucks. The 6.1 Hemi specifications are as follows:
The 6.1 Hemi also has a cast-iron engine block and aluminum cylinder heads. It maintains the same piston stroke as the 5.7 but increases the bore diameter to 103 millimeters (4.06 inches). These differences increased power output fairly substantially, as the Hemi 6.1 V8 makes a whopping 425 horsepower and 420 lb.-ft. of torque.
The Hemi 6.1 continued use through the 2010 model year. Then, it was replaced by the Hemi 392.
Hemi 392 6.4-liter V8
The Hemi 392 V8, once again, uses standard pushrod V8 construction like its smaller displacement counterparts. However, more modern advances grace its spec sheet.
For example, the Hemi 392 has four valves per cylinder rather than two. Additionally, it has a forged steel crankshaft and aluminum-alloy pistons.
It has a 103.9 millimeter (4.09 inches) bore and 94.6 millimeters (3.72 inches) stroke.
Additionally, it has a higher compression ratio at 10.9 to 1. The resulting power is an outstanding 485 horsepower and 475 lb.-ft. of torque.
The Hemi 392 continues production to this day and was recently added as an option to the 2021 Jeep Wrangler.
Though the Hemi 392 has outstanding power output, it does not quite hold a candle to the most powerful set of Hemi engines of them all.
Dodge Hellcat and Demon Hemi Engines
The fearsome Hellcat family has a remarkable supercharged Hemi V8 parked under the hood that makes power the original Hemi engine designers couldn’t possibly fathom for a production car.
While the Hellcat Hemi engine uses the same basic construction as the others, this engine was specially designed to ensure that it would make an absurd amount of power without negating its trustworthiness and ability to be used as a normal car.
To achieve this goal, the Hellcat V8 has a forged steel crankshaft and forged steel connecting rods.
Furthermore, forged steel pistons with a “diamond-like” coating on the wrist pins complete the package.
The bore remains the same as the Hemi 392 at 103.9 millimeters (4.09 inches), while the stroke is dropped to 91 millimeters (3.58 inches). The compression ratio is 9.5 to 1, which is impressively high for a forced-induction engine. The resulting power output is a breathtaking 707 horsepower and 650 lb.-ft. of torque. Newer versions of the Charger and Challenger Hellcat saw a power increase to 717 horsepower.
As if that wasn’t quite crazy enough, the 2018 Dodge Challenger SRT Demon came out with an even hotter version of the Hellcat V8 thanks to an upgraded supercharger. The Demon makes 808 horsepower on pump gas and 840 horsepower on racing fuel.
Finally, the Dodge Charger and Challenger Hellcat Redeye models come with 797 horsepower and 707 lb.-ft. of torque.
Are Dodge Hemi Engines Reliable?
There are plenty of examples of high-mileage equipped Hemi V8 vehicles for sale. While no engine is entirely free of problems, the Hemi family of engines is generally very reliable.
For example, the 5.7 Hemi engine has been in production for nearly 20 years, and the most prominent issue it has is known as the “Hemi tick.” This issue is the result of lifter-bearing failure. While it is relatively common in higher mileage examples, it is a relatively inexpensive fix and not a majorly detrimental failure.
Even the Hemi engines in Hellcats, which one would think are most prone to failure, have been racking up north of 100,000 miles without any monumental failures. There is currently a recall for 2017 Hellcat vehicles regarding an engine oil hose coming loose.
However, it is exclusive to the 2017 model year and likely has been taken care of on most models of that year.
Ultimately, buying a Hemi-powered vehicle is a perfectly safe bet. As always, ask for detailed maintenance records and run the VIN through our free VIN research tool to fully inspect the Vehicle’s history.
Photos: Dodge
