Hemi: The Engine That Was Buried Three Times

The hemispherical combustion chamber, from which the Hemi engine got its name, appeared long before Chrysler. Belgian Pipe, Italian Fiat, French Peugeot, and later Alfa Romeo, BMW, and Toyota experimented with a similar design at the turn of the 19th and 20th centuries. However, it was Chrysler engineers who were the first to bring this concept to a full-fledged production automotive engine. And the history of Hemi began not with cars, but with aviation.

During World War II, the company developed an experimental 16-cylinder XIV-2220 engine. It had a displacement of 36 liters and produced 2500 hp. In 1945, the engine was tested on a P-47 Thunderbolt fighter, which was able to exceed 500 miles per hour. The aviation unit did not reach mass production, but it was the work on it that gave Chrysler engineers experience with hemispherical combustion chambers.

Five years later, these developments were used for civilian vehicles. In 1951, Chrysler introduced its first automotive V8 with hemispherical chambers. Interestingly, the name Hemi was not yet used then. Within the company, the engine was called Double Rocker. Different divisions of the concern had their own names:

The first 5.4-liter FirePower developed 180 hp. For comparison, a Cadillac with a V8 of similar displacement produced 160 hp in those years. The additional power was explained by the design features. The hemispherical chamber dissipated heat better, allowed for larger valves, and more efficient cylinder scavenging.

But along with the advantages, serious disadvantages quickly became apparent. The valves in such a head were located at an angle to each other, not in the same plane. Because of this, the design required not one, but two rocker shafts. In addition, each combustion chamber required separate milling. There was also another problem: the hemispherical design was effectively limited to two valves per cylinder.

All this made the engine heavy and expensive. For example, the 392 Hemi weighed about 334 kg — almost a quarter more than most conventional V8s of that time. Therefore, such an engine could not become mass-produced. Even Dodge lasted with the first generation Hemi for only two model years — from 1953 to 1954.

Later, Chrysler engineers developed an intermediate option — polyspherical cylinder heads. This design already used one rocker shaft, was simpler, lighter, and cheaper to manufacture. And it was then that a very unpleasant thing for Hemi was discovered: the 354 cubic inch polyspherical engine of 1958 turned out to be more powerful than the full-fledged 1956 Hemi with a similar displacement.

After that, further production of the classic Hemi lost its meaning. In 1958, Chrysler finally switched to simpler wedge-shaped B and RB series engines. They had a displacement of 5.7 to 7.2 liters, were cheaper, lighter, and suitable for all corporate brands at once. Unification then became a matter of survival for Chrysler, so Hemi was quietly sent into history.

But not for long.

Already in January 1963, Chrysler engineers began work on a new engine for NASCAR and primarily for the Daytona 500. They took the production block of the wedge-shaped 426 engine as a basis and installed completely new hemispherical heads on it. This is how the legendary 426 Hemi appeared.

The main characteristics of the new engine looked impressive:

In those years, manufacturers often deliberately understated real power figures, and Chrysler was no exception.

Already in February 1964, Richard Petty, driving a Plymouth Belvedere with a 426 Hemi, won the Daytona 500, and with a huge advantage. The first three places in the race were taken by cars with Hemi, and by the end of the season, Chrysler engines won 26 victories in 62 NASCAR races.

The reaction was immediate: the engine was banned. Formally — because it was not available on production cars.

Chrysler missed the entire 1965 NASCAR season while engineers adapted the racing Hemi for regular roads. This is how the Street Hemi appeared. For civilian use, the engine was seriously redesigned:

In 1966, Chrysler returned to NASCAR, and Richard Petty again won the Daytona 500.

However, history repeated itself. The Hemi again turned out to be too expensive. The 426 Hemi option cost $908, while a basic Dodge Charger was priced at approximately $3100. Moreover, Chrysler gave only a one-year warranty on the Hemi, while conventional V8s had a five-year warranty. If the owner participated in drag racing, the warranty was completely voided.

Throughout its production — from 1966 to 1971 — approximately 10,500 426 Hemi engines were produced. For example, out of 37,344 Dodge Chargers sold in 1966, only 468 cars received a Hemi.

In the early 1970s, new environmental requirements and rising gasoline prices finally finished off the situation. In 1971, production was stopped again.

The next return of the Hemi took place only 32 years later. In 2003, Chrysler introduced a new 5.7-liter V8 with hemispherical chambers. The Dodge Ram pickup was the first to receive it, then the engine appeared on the Chrysler 300C, Jeep Grand Cherokee, Dodge Charger, and Challenger.

At the same time, engineers claimed that the new Hemi was more compact, lighter, and cheaper to produce even compared to the less voluminous 4.7-liter V8 PowerTech.

Later, the lineup expanded to several versions:

The supercharged Hellcats gained particular fame. The base Hellcat produced 707 hp, and the Hellcat Redeye version — already 797 hp. The 2018 Dodge Demon became a separate legend. On racing fuel, it accelerated to 100 km/h in just 2.3 seconds and covered a quarter mile in 9.65 seconds.

The Demon was the first production car capable of performing a full "wheelie" at launch. Because of this, the car was even banned by the NHRA.

It seemed that Hemi had again established itself in the market for a long time. But then history repeated itself for the third time. After the formation of Stellantis, the company decided to abandon the classic V8. In 2024, the 5.7-liter Hemi was removed from the Ram 1500, replaced by the new Hurricane inline twin-turbo six-cylinder.

The new engine indeed turned out to be more powerful and economical, but buyers reacted extremely coldly to the replacement. Ram sales went down: customers wanted precisely the V8 — with its characteristic sound and familiar character.

The situation changed on December 9, 2024, when Tim Kuniskis again took over as head of Ram. The very next day, he initiated a project to bring back the Hemi. Kuniskis later said that engineers initially planned to complete it in 18 months, but a separate team was able to bring the engine back in just six months.

In the summer of 2026, the 5.7-liter Hemi V8 officially returned to the Ram 1500. The characteristics remained the same — 395 hp and 410 Nm. On most versions, the surcharge for the engine is $1200, and in Limited and Longhorn trims, the engine is available without additional charge.

At the same time, instead of the familiar HEMI badge, a new symbol appeared on the fenders — Symbol of Protest.

It turned out to be an almost symbolic story. Over 75 years, the Hemi was discontinued three times: due to complexity, high cost, environmental concerns, and fuel consumption. But each time this engine returned — because for a huge number of Chrysler, Dodge, and Ram buyers, the Hemi has long ceased to be just an engine, but a part of the very idea of the American V8.

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