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"Hemi" - the world's definitive performance engine

8.2.06. Chrysler’s rich hot rodding history goes back over 50 years, and its roots can largely be traced to the introduction of the FirePower hemispherical head V8 engine to the domestic passenger car horsepower race in the 1950s.

The “Hemi”, as it soon came to be known, was designed to make optimum use of the low octane fuel available at the time, and featured cylinder heads with hemispherical combustion chambers (shaped like half a tennis ball) to increase thermal and volumetric efficiency.  The company’s engineers found that the configuration also displayed superior combustion characteristics and could easily adapt to higher-octane fuels.  The Hemi was not only Chrysler’s first “vee” engine, but also the most powerful and efficient passenger car motor available at the time.  

In 1951, the Hemi engine appeared in what was to be Chrysler’s first factory hot rod, the Saratoga, and later the New Yorker and Imperial models.  Boasting 180hp from its 331 cubic inches, the Hemi had a clear performance advantage over the company’s previous flathead six-cylinder engine, rated at just 115hp.  With a top speed of 106mph, it was perhaps not surprising that a New Yorker convertible was chosen as the Official Pace Car for the 1951 Indianapolis 500.

Over the years, the Hemi grew in specification and power, and by 1955, its output had climbed to an impressive 300hp, thanks to twin four-barrel carburettors, a full-race camshaft, solid lifters, special exhaust manifolds, a large-bore, dual exhaust system and modified PowerFlite automatic transmission.

Early hemi a tight fit in this '34 Ford hot rod

Significantly, it powered what is now widely acknowledged as the first true American muscle car – the Chrysler 300 “Letter Car”.  This was a big, heavy automobile, which still easily managed 127mph. 

Out on the track, the Chrysler 300 reigned supreme in NASCAR oval track racing, thanks in no small part to the Hemi engine.  “They came race ready,” said Tim Flock, who, along with Buck Baker, won NASCAR titles for Chrysler in the ‘50s.

In 1956, Chrysler introduced the 300B, fitted with a larger-capacity, 354 cu in Hemi that boasted 355hp.  A year later, the displacement rose again, to 392 cu in and 375hp, or for performance purists, an optional 390hp.  Even the less powerful version of the engine was capable of propelling the 300B from 0-60mph in 7.7 seconds and producing a quarter mile time of 17 seconds.

At around this time, a young Florida hot rodder by the name of Don Garlits was developing one of the first of a new breed of racing vehicles – the dragster.   Garlits realised that by making a car lower and longer, and positioning the driver behind the engine, over the rear wheels, to help increase traction, was a formula for great straight-line acceleration.  

Garlits realised the huge potential of the Chrysler engine after he went quicker down the quarter mile in his Hemi-equipped road car than in his custom-built dragster.  Predictably enough, it wasn’t long before the Hemi was installed in the frame rails of Swamp Rat 1, his first full-bodied dragster. That car went on to become the fastest dragster in 1957 and 1958 with its 454 cu in motor fed by eight carburettors.

In 1959, there was a brief glitch in the Hemi story, when Chrysler introduced the 413 cu in Wedge engine, which was lighter than the Hemi.  In 1963, the Wedge became the Max Wedge engine with a capacity of 426 cu in.  Coincidentally, Garlits brought his Wedge-powered Swamp Rat VI to England in 1964, for a Drag Racing festival at Blackbushe, and ran an 8.09-second quarter mile time at 197 mph in a demo run. 

Don Garlits on tour in England 1964 and below he gets a hole-shot on Tommy Ivo. 

Chrysler was far from done with the Hemi, however, and in 1964, introduced a new racing version with a displacement of 426 cu in (7 litres), similar to that of the Max Wedge.  It was this engine that was to rock the performance world with its ground-shaking power and ability to fry tyres at will.  The 426 Hemi went on to rule the racing world throughout the 1960s, while also providing the bedrock for modern, top-level drag race engine development.

The legendary 426 Hemi

The first Garlits car to utilise the 426 Hemi was Swamp Rat VIII, this 1500hp, supercharged monster running a best of 7.80 at 192 mph.  Over subsequent years, Garlits asserted his authority on the sport, pursuing a policy of remorseless innovation as he produced a succession of awesome, 426 Hemi cars.  He was the first driver to reach 240mph over the quarter mile, achieved in just 6.87 seconds.  He was the National Hot Rod Association World Champion in 1975, 1985 and 1986, with his Hemi- powered dragsters, and amassed a total of 53 NHRA Top Fuel national championship wins in an illustrious 25-year career in the sport. 

Out on the Bonneville salt flats the Hemi was also being put through its paces. Bob and Bill Summers built their famed Goldenrod quad-Hemi-engined land speed record contender and took the wheel-driven record at a remarkable 409.27mph in November 1965.  A total of 2,400hp was produced by the four petrol-fed, fuel-injected motors that powered the pencil-like projectile. 

Back in the car dealers’ showrooms, Chrysler introduced a succession of roadgoing, Hemi-powered cars throughout the ‘60s and ‘70s, including the Plymouth Satellite, Road Runner and Cuda, along with the Dodge Charger, Coronet and Challenger, all of which were available with an optional “Street Hemi”.  

"Hemi" made its mark in virtually every drag racing category

The Street Hemi incorporated an additional crankshaft vibration damper, forged pistons to allow a lower 10.25:1 compression, road camshaft, reduced valve spring rates, deep oil pan with baffles, large diameter oil pump, air cleaner, high-speed water pump and black valve covers.

Dodge commissioned Don Garlits to promote its new Challenger range of muscle cars for a major advertising campaign.  Garlits reported, “Now Dodge has gone and done the real thing.  Built the pony car of all pony cars.  The Dodge Challenger R/T; compact like a Dart, wide like a Charger.  Just the right size for anyone who likes his own personalised backyard bomb.”  

Out on the ovals, it was the famed Dodge Charger Daytona and Plymouth Superbirds that were setting the tracks alight throughout 1969 and 1970, their heavily streamlined bodies, incorporating a long nose and high rear wing, setting them apart from the pack.  Utilising the racing 426 Hemi, these cars were not only some of the most powerful, but also the most aerodynamic and fastest NASCAR racers of their era.

Bobby Isaac and crew at Bonneville after setting a new record.  Read the full story behind the record attempt at

Racer Bobby Isaac drove a Dodge Charger Daytona to a new closed course lap record of 201.10 mph at Talladega Speedway in 1970 and a year later went on to achieve 216.94 mph on the Bonneville salt flats.  Chrysler-powered cars went on to secure no fewer than 311 NASCAR race victories and were dominant in 1955 and 1956, from 1963 through to 1971, and then again in 1975 - most notably, with “The King’’, Richard Petty, at the wheel of his Plymouth.  

mechanical fuel-injection system was a favourite in competitions

During the 1970s, the legendary design of the Hemi engine was to provide the inspiration for a whole string of drag race engine developers.  Tuners such as Keith Black, Ed Pink, Donovan Engineering, to name but a few, took the immensely strong Hemi block design as the blueprint for their own, purpose-built, lightweight drag racing engines.   

The Keith Black aluminium Hemi block, introduced in 1974, was so successful that it held all the national records in the elite Top Fuel category between 1975 and 1984.  Even now, the latest, mega-horsepower engines in Top Fuel can trace their roots to the famed Hemi.  

The original Hemi is available with an updated specification for increased strenghth and longevity as a crate motor from Mopar dealers, while the latest generation, fuel injected Hemi, is now on sale in a plethora of new Chrysler product (below)

Such has been the demand for this ultimate hot rod engine that, in recent years, it has been reintroduced for specific applications, and is now available off-the-shelf from American Mopar dealers.  Of equal significance is Daimler Chrysler’s rekindled love of this iconic V8 engine, and the fact that a new version has been introduced throughout the latest Chrysler vehicle range.  The Hemi looks like it’s here to stay, and automotive performance enthusiasts around the world can rejoice.

Story: Andy Kirk

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