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HEMI THE 125YR STORY

History of the Hemi Engine

The Unbelievable Story of the Hemi Engine Design.

“For 125 years this very engine design has stood the ultimate test of time. Throughout its long life and varied incarnations it’s continued to prove itself. 

It stretches ones imagination how long it has been in production.

The perfection of the Hemi engine.”

Von Richards

Most of us motor-heads are quite familiar with the Hemi engine. When we hear the word Hemi it conjurers up the famed Chrysler Hemi’ 392, and in particular the legendary 426 Hemi. However there are some history buffs who may know of the design much earlier. A little back ground about the hemispherical combustion chambers going back to the 1900’s and even used in WWII.

Belgian carmaker Pipe produced a four-cylinder Hemi

The basis of the Hemi design is fairly simple. The shape of the cylinder head’s combustion chamber is approximately half of a sphere—picture a grapefruit cut down the middle and hollowed out. This allows the spark plug to be placed top-center, which shortens the burn distance of the air/fuel mixture. At the same time, on overhead-valve engines, a large intake and exhaust valve is fitted on either side of the plug to enhance intake air and exhaust flow in and out of the combustion chamber. Due to the hemisphere shape, flattop pistons could not produce sufficient compression, so domed pistons were used to make up the difference. 

Even at its most basic stages of development, the hemispherical configuration proved to augment the combustion process and increase engine power.

Earliest Hemi’s

Fiat 130 Grand Prix Race Car circa 1907

The Hemi design actually came into existence with some of the earliest automotive internal combustion engines.’Belgian carmaker Pipe produced a four-cylinder Hemi in 1905, and the Fiat 130 HP Grand Prix race car brought it to the track by 1907′. Several manufacturers followed suit with the more powerful combustion-chamber technology through the coming decade.

 

Chrysler Hemis

Overall Hemi-style, combustion-chamber production dropped off due to cost issues subsequent to the power rush of the originals, but Chrysler prompted a rebirth following World War II.

Chrysler engineers committed themselves to the testing and development of Hemi engines throughout the war for military and aeronautic use. There were two experimental models completed. One was the V-12 AV-1790-5B engine used in the M47 Patton tank. The other was the massive XIV-2220 (a 2,220ci V-16) to power a P-47 Republic Thunderbolt fighter aircraft. The XIV-2220 was rated at 2,500 hp and surpassed 500 mph on test flights. Although the project was considered a success, the end of the war and oncoming of jet aircraft technology eliminated demand, and the V-16 never made it into production.

First Generation Hemi (1951-1958)

Hemi knowledge gained during and post-WWII hit the street in 1951 with the production of Chrysler’s first overhead-valve V-8, replacing the flat head (which had its valves in the cylinder block). The cast-iron, 331ci “FirePower” engine was rated at 180 hp.

Some of Chrysler’s divisions created their own dissimilar inline-six and V-8 Hemi versions, although Plymouth did not incorporate a first-generation Hemi into its lineup.

Chrysler and Imperial: FirePower (331, 354, 392 ci)

Desoto: Fire Dome (276, 291, 330, 341, 345 ci)

Dodge: Red Ram (241, 270, 315, 325 ci), Power Giant (354 ci), intended for heavy trucks.

Second Generation (1964-1971): The 426

From a baby-boomer perspective, the 426 is the definition of a Hemi. After a stall in production following the first generation, Chrysler produced what some called the “Elephant Engine.” This was the first hemispherical head design engine to wear the trademark HEMI name.

The 426ci extra big-block was originally built for NASCAR racing inside the ’64 Plymouth Belvedere. The new breed of Hemi swept the top three spots at the Daytona 500. But the Hemi was banned by new regulations in 1965 due to Chrysler’s lack of Hemi street sales and complaints from competitors of an unfair power advantage. Some Dodge Dart, Coronet, and Plymouth Fury models were sold to the public with the race version of the 426, but significant production of milder street configured engines didn’t begin until 1966. This permitted Hemi-equipped stock cars a return to the NASCAR circuit.

The street Hemi was toned down with a lower compression ratio (10.25:1, compared to the race engine’s 12.5:1), replacement camshaft, milder intake and exhaust manifolds, and possibly more. But still put out a respectable 425 hp.

Street Hemi Models

           

Dodge

Challenger (1970-1971), Charger (1966-1971), Charger Daytona (1969), Coronet (1966-1970), Dart SS (1968), Super Bee (1968-1971) 

Plymouth

Barracuda/’Cuda (1970-1971), Barracuda SS (1968), Belvedere (1966-1970), Fury GT (1970), GTX (1967-1971), Road Runner (1968-1971), Satellite (1966-1971), Superbird (1970)

The 426 HEMI is a muscle-car legend, and for good reason. Hemi-equipped street-car sales ended at the ’71 model year, but the race-car industry caught the drift. The NHRA Top Fuel class features the most powerful race cars in the world, with engine’s pumping out 11,000 hp at the crankshaft. These carbon-fiber-bodied dragsters and Funny Cars exceed 300 mph in less than 4 seconds over a span of 1,000 feet.

Here’s what a lot of folks believe is the most impressive facet of the Elephant Engine’s history. These 500ci, nitromethane-burning monsters are aluminum, modified, supercharged replicas of Chrysler’s second-generation 426 HEMI—maintaining basically the same hemispherical-style, two-valve combustion chamber cylinder heads.

Classic Hemi muscle cars are at the top of a few collectors’ to-do lists. Chrysler sold just 16,159 Plymouth Barracudas for the ’71 model year; 119 were the famed Hemi ’Cuda, 11 of which were convertibles. Only two of those convertibles were equipped with a four-speed transmission. One of those two manual-transmission, Hemi-powered Plymouth convertibles sold at auction in 2014 for $3.5 million.

Varied Iterations of the Hemi

Motor vehicle, Mode of transport, Automotive design, Vehicle, Car, Motorsport, Automotive exterior, Performance car, Touring car racing, Automotive parking light, LEGEND OF LEGENDS….

 

Von Richards

Copyright Global Media 12.4.24

 

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