Chrysler Hemi engine: Everything you need to know

There’s a famous advertising catch-cry in North America: `Yeah, it’s got a Hemi’. And that five-word phrase was enough to gain the attention of performance-car lovers in no uncertain terms.

But what is a Chrysler Hemi engine and why is it so special?

Actually, that’s not exactly a simple question to answer, because there have been, in effect, four engine series from the Chrysler family that have carried the Hemi marketing tag. And one of those was an Australia-only family of powerplants.

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Meantime, what is a (lower case `h’) hemi engine? It all comes down to the shape of the combustion chamber; the space in the engine where the air and fuel actually burns to create torque which is the force that turns the crankshaft and, ultimately, the car’s wheels.

And what does Hemi mean? Basically, that this combustion chamber is shaped like half a tennis ball, or roughly hemispherical, hence Hemi. That places the spark plug roughly in the centre of the combustion chamber for good flame propagation and allows for a large intake and exhaust valve (bigger valves mean more air and fuel in and out). 

The cross-flow design where the air and fuel enters on one side of the combustion chamber and exits on the other side) also helps with overall efficiency.

Chrysler is by no means the only carmaker to have used a hemispherical combustion chamber, but thanks to the magic of marketing, it’s the brand that has become most closely associated with the layout. 

As early as 1907, Fiat had realised the potential of the hemi design and had taken it to race tracks with its Grand Prix car.

Interestingly, the advent of multi-valve cylinder heads has slowed the production of engines with the hemispherical design as it lends itself better to two large valves rather than four smaller ones. 

But lots of manufacturers over the years have used a hemi design, even if they’ve not referred to it as such for fear of giving Chrysler a free kick.

In Chrysler’s case, the first engines to use a Hemi layout were a pair of engines designed for military use in a tank and a fighter plane. 

The end of the war and acceleration of the jet age killed off both projects, but Chrysler engineers could see the benefits of the tech and used it for a family of car engines that went on sale just a handful of years after World War 2.

That first-gen Hemi V8 was built from 1951 to 1958 and represented Chrysler’s first production overhead valve V8s. The line-up started with the 331 cubic inch (5.4 litre) 'FirePower' and 'FireDome' engines which eventually grew to the 392 Hemi (6.4 litres).

The 1957 300c was powered by a 6.4-litre Firepower V8.

But better was to come. That arrived in 1964 with the second-gen Hemi for North America. Dubbed the Elephant Engine by some for its sheer physical bulk, the 426 cubic inch (7.0-litre) Hemi was originally developed for NASCAR racing but has since gone on to dominate the world of drag racing, as well. 

Eventually banned by NASCAR for being too fast, the 426 Hemi found its place powering some of Chrysler’s most iconic muscle cars including the Plymouth Barracuda (also known as the Hemi Cuda with this engine fitted) Road Runner and GT-X and Dodges including the Charger, Challenger and Super Bee. 

Around 2000 Superbirds were built.

Some tuners managed to stretch the 426 to a 572 Hemi and these are now available as aftermarket crate engines. 

People also think of Chrysler’s 440 cubic inch V8 in this context, but the 440 was actually not a Hemi design and was from Chrysler’s `Magnum’ or `Wedge’ family of V8s. (You can now buy a 440 Hemi, but it’s an example of the aftermarket Hemi crate engines based on the third-gen V8 Hemi.)

Speaking of which, the third family of Chrysler V8s to use the Hemi tag came along in 2003 in 5.7-litre form and then progressing through to 6.1 and even 6.4 Hemi displacements. 

The 300c had two V8 options, 5.7 or 6.1 litres.

These engines will be more familiar to many Australian motorists as they powered the V8 versions of Chrysler’s 300C models which launched here in 2005. 

In its ultimate form, the latter-day Hemi V8 could be had in 6.2-litre, supercharged form in which it produced more than 700 horsepower (522kW) and was available in the US-market Dodge Charger and Challenger Hellcat models. 

2015 Dodge Challenger SRT Hellcat.

It was also sold in Australia in the Hemi Jeep Grand Cherokee and the supercharged, Hellcat-powered Grand Cherokee Trackhawk. 

Jeep Hemi engines were a straight lift from the Chrysler parts catalogue as both companies were under joint ownership. 

More recently, Australia has also seen the rise of the North-American RAM utility, most notably with the RAM 1500 Hemi engine under its broad bonnet.

The 1500 is powered by a 5.7-litre V8.

But there’s another version of the Chrysler Hemi that Australia car owners of a certain age will also be familiar with. 

Back in the 1960s, Dodge in the US was looking for a new engine to replace the old slant-six truck motors that had served it so well. An overhead-valve design was sketched up but, ultimately, Dodge lost interest and shelved the project. 

That’s where Chrysler Australia (as part of the Chrysler global family) stepped in and took over the project, finishing the designs to create the fabulous 215 Hemi, Hemi 245 and 265 Hemi straight-six engines that powered a couple of generations of Valiant cars and utes in the 1970s and into the '80s. 

Chrysler Australia introduced the Hemi six engines in 1970.

Aussie Hemi engine sizes ranged from 3.5 litres (215 cubic inches) through 4.0-litre (245) and 4.3 litres (265). They were also known as the Dodge Hemi when fitted to Dodge-badged light trucks and utes here.

Although not a V8, these engines had all the performance of a small-capacity V8 and lots of torque into the bargain. In its ultimate form, the 265 cubic-inch (4.3-litre) version sprouted three Weber carburettors and ran a fighting third at Bathurst in 1972 (the year of Peter Brock’s first win at Mount Panorama). 

With 225kW/440Nm, the 265 Hemi was the most powerful six cylinder engine in the world.

Known in this form as the 'Hemi Six Pack', it stands as one of this country’s best ever (and most collectible) muscle cars.

Known for their toughness and durability, the biggest reliability problem with the Australian Hemi six is a tendency for the camshaft to 'walk' along the length of the engine thanks to poor camshaft location. When this happens, the ignition timing can be thrown out. 

It’s also worth mentioning that the Aussie Hemi six is not, in fact, a true Hemi at all. The cylinder head doesn’t use a cross-flow layout and the combustion chamber is not a 'true' hemispherical shape. 

The Hemi tag was more about marketing than engineering, but there’s no doubting the engine’s performance credentials, even currently.

Buying a Hemi now to repower a car or to complete a project will very much depend on the engine you’re after. 

US Hemi V8s from the first generation are getting scarce and you could easily pay several thousand dollars for an engine needing full refurbishment. 

The same, only more so, goes for the fabled second-gen Hemi 426. Finding one will be difficult and then you’ll need lots of dollars to prise it from its owner’s grasp. 

A third-gen Hemi is much easier to find both as a second-hand unit form a wrecking yard or a crate engine in brand-new condition. 

Prices start at a couple of thousand for running units to crate engines at around US$7000 and up all the way to US$20,000 for a Hellcat crate engine.

For an Australian Hemi six, second-hand runners can be found for a few hundred dollars, but a reconditioned unit will be several thousand dollars depending on where you shop and the engine’s final specification. 

Either way, you’ll be buying second-hand or reconditioned, so check the Hemi engine for sale classifieds first.