Race Hemi 426
Chrysler stopped producing the first generation Hemi engines in the late ’50s due to the rising costs of production and somewhat delicate mechanics. Due to their performance potential, early Hemis, especially the 392 V8 were popular with racers. So, in the early ’60s when Chrysler wanted to go racing, their engineers proposed a new, second-generation Hemi. It would have improved mechanics, bigger displacement and most importantly, lots more power.
In 1964, the race Hemi 426 was not a street-legal engine but in fact, a racing motor. It had 12.5:1 high compression heads and a special intake system and manifold, as well as a new 7.0 liter block featuring 426 CID of displacement. They intended the new race Hemi 426 for use in drag racing and NASCAR racing. Depending on the application, the power was from around 500 HP to over 800 HP.
Different championships had different propositions and regulations, so for NASCAR, the intake was limited. But, for NHRA drag racing, lots of racers used fuel injection and multiple carburetor set up, so the power levels varied. However, the new race Hemi 426 was a clear winner as soon as it came out in 1964.
Street Hemi 426
Due to the high demand from performance enthusiasts to produce a street version of a race Hemi, Chrysler started developing a street legal set up for its Plymouth and Dodge products. Chrysler couldn’t use the Hemi engine since the nature of the 426 Hemi didn’t mesh with its restrained, luxurious brand image. However, for the lower-priced Dodge and Plymouth brands, this engine was the perfect addition to their lineup and a strong attention-getter.
They presented the street version of the mighty 426 Hemi in 1966. It featured a four-barrel carburetor and a lower 10.5:1 compression ratio with the same basic block and heads as the race variant. The factory rated the 426 Hemi at 425 HP but it was clear the engine produced more. In fact, most historians agree the real output of the 1966 to 1971 street Hemi was over 500 HP.
Such power required a heavy-duty suspension, frame and gearbox as mandatory options. Today, those original Hemi cars are extremely expensive and rare. This is because they only produced about 10,000 original 426 Hemi engines from 1966 to 1971. Chrysler stopped production in 1971 since the Hemi was not compliant with the newly-introduced emissions standards.
They also installed Hemi engines in numerous racing cars and racing boats. In fact, they even put them in a few models of other small manufacturers, such as the Monteverdi Hai 450. Due to enormous power and tuning ability, car fans consider the Hemi 426 the most legendary engine of all time.
5.7-Liter Hemi V8
For over 30 years, Chrysler didn’t produce a Hemi engine or anything like the original concept. The company produced a lot of interesting, powerful engines, but nothing with hemispherical combustion chambers. Although the Hemi was absent from the market after 1971, the popularity was bigger than ever. That was especially due to classic muscle cars becoming popular and highly sought-after collectibles.
That is why Chrysler decided to revive the Hemi engine, although in modern form with modern construction techniques and materials. In 2003, they installed the first modern Hemis in the Dodge Ram. It featured 5.7-liter displacement and 345 HP.
The basic construction with two valves per cylinder and the push-rod design stayed true to the original concept from 1951. You can find the modern 5.7 Hemi in numerous Chrysler, Dodge and Jeep models up until 2009 when it received its first makeover.
5.7-Liter Eagle Hemi V8
For the 2009 model year, Chrysler revised its popular Hemi with numerous upgrades including Variable Camshaft Timing. It also featured cylinder heads with a better flow, an upgraded engine electronic system and a new generation of the Multi Displacement System (MDS).
The power output had risen, so the base 5.7 Hemi now produces 363 HP to 395 HP in some applications. Despite the archaic construction design, modern Hemi engines are surprisingly efficient and compliant with all emissions standards.
6.1-Liter Hemi V8
The modern Hemi engine provides a great basis for further development, so it was not long before Chrysler introduced the next version. It came with upgraded displacement, power and torque. In 2005, in the SRT models of Chrysler, Dodge and Jeep, the new Hemi performance version appeared.
It was a 6.1-liter Hemi with different blocks and heads to allow better cooling and flow. The power output was hefty at 425 HP. That was a new milestone for naturally aspirated engines. Also, this was an interesting historical moment since the new Hemi matched the output of the old 426 Hemi engine, or at least the advertised output.
6.2-Liter Hellcat V8
The most popular, highly sought after third-generation Hemi engine is the famous 6.2-liter Hellcat V8. This engine was born when Chrysler engineers mounted an enormous 2.4-liter supercharger on top of the already powerful stock Hemi V8.
The result was astonishing with 707 HP and 650 lb-ft. It is one of the most powerful street-legal engines currently on the market as well as one of the most powerful muscle engines ever. They first intended it for installation in the Challenger Hellcat. However, due to high demand, it is available in the Charger Hellcat and from 2018, in the Jeep Cherokee Trackhawk, too.
6.2-liter Hemi Demon V8
If you think the insane Hellcat V8 with 707 HP is not powerful enough, there is the 6.2-Liter Demon V8 built by the same guys in the Chrysler SRT department. This powerplant delivers 820 HP and is available in limited production. It is also in the track-ready Dodge Challenger Demon.
The Demon is more than a Hellcat with more boost and over 100 HP more. Even though these two engines share similar architecture and blocks, there are over 25 important differences between the two.
6.4-Liter 392 Apache Hemi V8
The last engine on this list started as a crate engine that the Chrysler Mopar division produced. They based the Apache Hemi V8 on the revamped 5.7-liter version. The 392 is a naturally-aspirated Hemi with performance additions. The output is 532 HP and 510 lb-ft of torque. They introduced this engine in 2007 as a crate engine, but in 2011 they installed it in the Dodge Challenger SRT.
Since they offered this unit as a replacement engine and crate item, it proved to be popular with restomod guys. In fact, the 392 was the perfect replacement engine for people who wanted to restore older muscle cars but also give them a modern drivetrain and drivability. The 392 Hemi V8 with 532 horses had almost the same HP as the original 426 Hemi. But, it was much more docile on the street and easier on fuel, too.
The powerful and dependable Hemi engine is legendary and world renown. Fortunately, car manufacturers will continue to use the Hemi in future production models, improving it with each generation. No one wants to see the famous Hemi engine go away, so it should be around for many years to come.