Chrysler Hemi
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The Chrysler Hemi engines, known by the trademark Hemi, are a series of American V8 gasoline engines built by
Chrysler Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automotiv ...
with
overhead valve An overhead valve (OHV) engine, sometimes called a ''pushrod engine'', is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with earlier flathead engines, where the valves were located be ...
hemispherical combustion chambers. Three different types of Hemi engines have been built by Chrysler for automobiles: the first (known as the Chrysler FirePower engine) from 1951 to 1958, the second from 1964 to 1971, and the third beginning in 2003. Although Chrysler is most identified with the use of "Hemi" as a marketing term, many other auto manufacturers have incorporated similar designs. The engine block and cylinder heads were cast and manufactured at Indianapolis Foundry. During the 1970s and 1980s, Chrysler also used the ''Hemi'' name for their Australian-made Hemi-6 Engine and applied it to the 4-cylinder Mitsubishi 2.6 L engine installed in various North American market vehicles.


Concept

A hemispherical
cylinder head In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas in more modern o ...
("hemi-head") gives an efficient combustion chamber with an excellent surface-to-volume ratio, with minimal heat loss to the head, and allows for two large valves. However, a hemi-head allows no more than two valves per cylinder, and these large valves are necessarily heavier than in a
multi-valve In automotive engineering a multi-valve or multivalve engine is one where each cylinder has more than two valves. A multi-valve engine has better breathing and may be able to operate at higher revolutions per minute (RPM) than a two-valve engi ...
engine. The intake and exhaust valves lie on opposite sides of the chamber and necessitate a "
cross-flow Crossflow may refer to: * Ford Crossflow, the 1967 version of the Ford Kent engine * Crossflow cylinder head * Cross-flow fan, a type of mechanical fan * Cross-flow filtration, a filtration technique * Cross-flow turbine A cross-flow turbine, B ...
" head design. Since the combustion chamber is a partial hemisphere, a flat-topped piston would yield too low a
compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stati ...
unless a very long stroke is used, so to attain the desired compression ratio the piston crown is domed to protrude into the head at top dead center. The result is a combustion chamber in the shape of the space between where the domed piston stops and the dome shape in the head receiving it. The hemi-head design places the
spark plug A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/ai ...
at or near the center of the chamber to promote a strong flame front. However, if the hemi-head hemisphere is of equal diameter to the piston, there is minimal squish for proper turbulence to mix fuel and air thoroughly. Thus, hemi-heads, because of their lack of squish, are more sensitive to fuel
octane rating An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without detonating. The higher the octane number, the more compression the fuel can withstand before detonatin ...
; a given compression ratio will require a higher octane rating to avoid pre- detonation in a hemi engine than in some conventional engine designs such as the wedge and bathtub. The hemi head always has intake and exhaust valve stems that point in different directions, requiring a large, wide cylinder head and complex
rocker arm In the context of an internal combustion engine, a rocker arm is a valvetrain component that typically transfers the motion of a pushrod to the corresponding intake/exhaust valve. Rocker arms in automobiles are typically made from stamped steel ...
geometry in both cam-in-block and single overhead cam engines (dual overhead cam engines may not have rocker arms). This adds to the overall width of the engine, limiting the vehicles in which it can be installed. Significant challenges in the commercialization of engine designs using hemispherical chambers revolved around the valve actuation, specifically how to make it effective, efficient, and reliable at an acceptable cost. This complexity was referenced early in Chrysler's development of their 1950s hemi engine: the head was referred to in company advertising as the ''Double Rocker Shaft'' head.


World War II

Chrysler developed their first experimental hemi engine for the
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P-47 Thunderbolt The Republic P-47 Thunderbolt is a World War II-era fighter aircraft produced by the American company Republic Aviation from 1941 through 1945. It was a successful high-altitude fighter and it also served as the foremost American fighter-bomb ...
fighter aircraft. The XIV-2220 engine was an inverted V16 rated at . The P-47 was already in production with a
Pratt & Whitney Pratt & Whitney is an American aerospace manufacturer with global service operations. It is a subsidiary of Raytheon Technologies. Pratt & Whitney's aircraft engines are widely used in both civil aviation (especially airlines) and military av ...
radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ...
when the XIV-2220 flew successfully in trials in 1945 as a possible upgrade, but the war was winding down and it did not go into production. However, the exercise gave Chrysler engineers valuable research and development experience with two-valve hemi combustion chamber dynamics and parameters. In addition to the aircraft engine, Chrysler and Continental worked together to develop the air-cooled AV-1790-5B V12 Hemi engine used in the
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tank.


First generation: FirePower

Chrysler applied their military experience with the hemispherical combustion chamber to their first overhead-valve
V8 engine A V8 engine is an eight-cylinder piston engine in which two banks of four cylinders share a common crankshaft and are arranged in a V configuration. The first V8 engine was produced by the French Antoinette company in 1904, developed and u ...
, released under the name FirePower, not "Hemi," in 1950 for the 1951 model year. The first version of the FirePower engine had a displacement of and produced . Eventually, three of the four Chrysler divisions had their own version of the FirePower engine, with different displacements and designations, and having almost no parts in common. This lack of commonality was due in part to the three engine versions using different bore pitches (the center-to-center distance between adjacent cylinders). Chrysler and
Imperial Imperial is that which relates to an empire, emperor, or imperialism. Imperial or The Imperial may also refer to: Places United States * Imperial, California * Imperial, Missouri * Imperial, Nebraska * Imperial, Pennsylvania * Imperial, Texas ...
called their versions the ''FirePower''. DeSoto called theirs the ''FireDome''. Dodge had a smaller version, known as the ''Red Ram''. Only
Plymouth Plymouth () is a port city status in the United Kingdom, city and unitary authority in South West England. It is located on the south coast of Devon, approximately south-west of Exeter and south-west of London. It is bordered by Cornwall to ...
did not have a version, but retained the Dodge poly-head engines. There was no Plymouth hemi engine until the 1964 426.
Briggs Cunningham Briggs Swift Cunningham II (January 19, 1907 – July 2, 2003) was an American entrepreneur and sportsman. He is best known for skippering the yacht ''Columbia'' to victory in the 1958 America's Cup race, and for his efforts as a driver, team o ...
used the Chrysler version in some of his
race car Auto racing (also known as car racing, motor racing, or automobile racing) is a motorsport involving the racing of automobiles for competition. Auto racing has existed since the invention of the automobile. Races of various sorts were organise ...
s for international motorsports. A Chrysler-powered Cunningham C-5R won its class in 1953. Cunningham switched away from these designs in 1959 when Chrysler temporarily abandoned the hemispherical concept in favor of the wedge-head B engine until 1964. Carl Kiekhaefer also used the Chrysler engines in NASCAR cars owned by him from 1955 and 1956, winning the Grand National Series championship both years. Collectively, the 1951–1958 Hemi engines are now commonly referred to as first-generation Hemi engines, and the group can be identified by the rear-mounted distributor and the
spark plug A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/ai ...
s in a row down the center of wide valve covers.


1951 Plymouth Hemi V6

There were plans in 1951 for a
Plymouth Plymouth () is a port city status in the United Kingdom, city and unitary authority in South West England. It is located on the south coast of Devon, approximately south-west of Exeter and south-west of London. It is bordered by Cornwall to ...
Dual Overhead Cam Hemi V6 displacing designed by Chrysler's Powerplant Research and Engine Design division. It was meant to be a powerful, fuel-efficient alternative to Ford's V8 and to replace Plymouth's venerable flathead 6. The plans were scrapped due to build costs and because of the then unusual design.


Chrysler and Imperial

All Chrysler FirePower engines are oversquare; i.e. their bore is larger than their
stroke A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorr ...
.


331

This first FirePower engine, used from 1951 to 1955, has a bore of 3.8125 in and a stroke of 3.625 in for a piston displacement of , and a deck height of 10.32" ("low deck"). The bore pitch, shared by all Chrysler FirePower engines, was 4.5625", the largest of any 1st generation hemi engines. Most used a two-barrel
carburetor A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main meteri ...
and produced , with the famous exception of the 1955 Chrysler C-300 equipped with dual Carter WCFB four-barrel carburetors and rated at . The 331 engine was used in the following applications: * 1951–1955
Chrysler New Yorker The Chrysler New Yorker is an automobile model that was produced by Chrysler from 1940 until 1996, serving for several decades as the brand's flagship model, or as a junior sedan to the Chrysler Imperial luxury brand. A trim level named the "New ...
* 1951–1954
Chrysler Imperial The Chrysler Imperial, introduced in 1926, was Chrysler (division), Chrysler's top-of-the-line vehicle for much of its history. Models were produced with the Chrysler name until 1954, after which it became Imperial (automobile), a standalone bra ...
and 1955
Imperial Imperial is that which relates to an empire, emperor, or imperialism. Imperial or The Imperial may also refer to: Places United States * Imperial, California * Imperial, Missouri * Imperial, Nebraska * Imperial, Pennsylvania * Imperial, Texas ...
* 1951 Chrysler Saratoga * 1952 Chrysler Saratoga Club Coupe * 1952
Chrysler Imperial Parade Phaeton Three Chrysler Imperial Parade Phaetons were produced in 1952 by Chrysler as ceremonial vehicles. They were styled by Virgil Exner and were in many ways a preview of the new "100 Million Dollar" styling that would debut in 1955 on the newly separat ...
* 1955 Chrysler C-300 * 1956
Facel Vega FVS The Facel Vega FV/FVS is a car produced by French automaker Facel from 1954 until 1959. It continued until 1962 as the HK500. History FV The Facel 'Vega' was launched at the 1954 Paris Salon. By 1956, the cars were called FVS (for Facel Vega ...
* The
Chrysler air raid siren The Chrysler Air Raid Siren (second generation), or known as the Chrysler Bell Victory Siren (first generation) is an outdoor warning siren produced during the Cold War era that has an output of 138 dB(C) at . History Built during the Cold Wa ...
. At 138
decibel The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a ...
s, it is the loudest siren ever made.


354

The , released in 1956, had a bore of 3.9375 in and stroke of 3.625 in, and the same 10.32" low deck height. The 300B engine was rated at , while the New Yorker and Imperial 354 engine configuration produced . For the 300B an optional version was available, making it the first American V8 to be rated at one horsepower per cubic inch. Note that was before 1972, horsepower was SAE gross. After 1972, horsepower is SAE net. The 354 was also modified. The hemi was optimized for heavy-duty truck service. These were available with one or two four-barrel carburetors, and were offered in Dodge's heaviest-duty models as the 'Power Giant V-8' from 1957 through 1959; they were the largest of four hemi truck engines offered by Dodge in the 1950s. The 354 was also offered in certain models with polyspheric heads rather than hemi heads. The combustion chambers on these had similarities to both hemi and wedge heads, but were closer in weight to wedge heads. Thus, both 354 poly and 354 hemi V8 engines were variously available in 1957. The 354 engine was used in the following applications: * 1956 Chrysler New Yorker * 1956 Chrysler 300B * 1956 Imperial Custom & Crown * 1957 Dodge D-501 * 1957–1959 Dodge C Series Pickup


392

The 392 raised-deck engine released in 1957 had a bore and stroke. The actual displacement is . The deck height, at , was taller than that of the previous blocks. Because its deck was taller, the heads were cast with wider intake ports so that earlier manifolds could be used with the new heads on the new taller block. For 1958, Chrysler offered the 392 in two configurations: with 9.25:1 compression and with 10:1 compression, both with a single four-barrel carburetor. A dual four-barrel version of the 392 available in the 1957-58 Chrysler 300C & 300D cars was rated at ; the 300D, and some marine and industrial engines, used a (now rare) adjustable rocker.''Hot Rod'' Magazine online
(retrieved March 9, 2018)
An extremely rare option available on the 1958 300D was Bendix "Electrojector"
fuel injection Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines. All com ...
, with which the 392 was rated at . Due to reliability problems with the primitive onboard computer which controlled the injection system, however, 15 of the 16 300D cars built with the fuel injection option were recalled and retrofitted with carburetors. The 392 engine was used in the following applications: * 1957–1958 Chrysler New Yorker * 1957–1958 Imperial Custom, Crown, and LeBaron * 1957
Chrysler 300C The Chrysler Corporation has used the designation Chrysler 300C to refer to two separate unrelated vehicles from different eras: * The 1957 Chrysler 300C is that year's version of the Chrysler 300 "letter series"; a large, high-performance luxury ...
* 1958 Chrysler 300D * 1958
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(EX) In the late 1950s and early 1960s, drag racers found the 392 to be a formidable engine and continued to run them competitively into the 1970s. Usual color of the block was silver.


DeSoto

DeSoto's Hemi engines were called FireDome and served as the naming convention for the DeSoto Firedome sedan.


276

In 1952, DeSoto introduced its version of the FirePower with a bore of and stroke of , for a displacement of . The bore pitch, shared by all DeSoto FirePower engines, was . Power output was . It was a hot seller, with 50,000 vehicles using the engine until it was replaced in 1954.


291

An increase in displacement to was made for 1955 by increasing the bore to .


330

The DeSoto engine was enlarged for 1956 to . Bore was the same as the 291 at , but stroke was increased to and a taller (raised-deck) block was used.


341

Displacement was increased again for 1956 (DeSoto Adventurer only) and 1957 (Firedome and Fireflite models) to . Bore was now with stroke remaining at . The DeSoto Adventurer produced using dual Carter WCFB four-barrel carburetors. The 1956 DeSoto Adventurer was the premiere named high-performance version—the DeSoto equivalent of the Chrysler 300—using dual Carter WCFB four-barrel carburetors. The Adventurer engine for 1956 used a displacement of 341 CID (3.78" bore by 3.80" stroke) and had a compression ratio of 9.5:1, using a special hydraulic camshaft profile.


345

The largest DeSoto engine for 1957 was the DeSoto Adventurer offering with square bore and stroke dimensions of 3.80 inches. The DeSoto Adventurer used dual Carter WCFB four-barrel carburetors for a rating of , producing one horsepower per cubic inch (the first American car to do so as standard equipment) utilizing a similar intake manifold to the 1956 341 Adventurer and a similar camshaft. The compression ratio remained at 9.5:1.


Dodge

Dodge's Hemi was introduced in 1953 as the Red Ram. Dodge did not have a V8 engine until one was developed specifically for the line in 1953 based on the 1951
Chrysler Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automotiv ...
hemi design, but downsized for these smaller cars. They have the smallest bore center distance of any hemi engine at . They do not share any major dimensions or components with the larger Chrysler and DeSoto hemi engines, or the Plymouth A engines. From 1955 to 1958 (see 1956 D500 Dodge D-500 cars and packages: early performance cars) lower-performance versions of the Dodge hemi were introduced by substituting less complex poly (single rocker shaft) heads and valve train parts, including one variant only built as a poly (259"). These were used in low-line 1955-58 DeSotos and Dodges, and 1955-56 high-line Plymouths. Dodge Trucks marketed their version of the Hemi under the name PowerDome.


241

Dodge introduced the engine in 1953. Bore was and stroke was . With a low compression ratio of 7.0:1 (in 1953 and for the 1954 Meadowbrook), the 241 produced . For 1954, the more senior Dodges received thanks to a higher 7.5:1 compression ratio.
Lee Lee may refer to: Name Given name * Lee (given name), a given name in English Surname * Chinese surnames romanized as Li or Lee: ** Li (surname 李) or Lee (Hanzi ), a common Chinese surname ** Li (surname 利) or Lee (Hanzi ), a Chinese ...
, p. 270
This engine is not the same as the Plymouth 241, which had polyspheric, not hemi heads. The 241 only lasted two years, being replaced by the 270 for 1955.


270

The D553 1955/1956 Dodge Red Ram Hemi 270 displaced and was used in premium 1955 and 1956 Dodge vehicles. Bore was and stroke was . It was not the same as the 270 poly-head. In the Dodge Coronet, running 7.6:1
compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stati ...
, the 270 produced . In higher trims like the Dodge Royal, the "Super Red Ram" ran the same compression ratio but with a four-barrel carburetor produced .
Lee Lee may refer to: Name Given name * Lee (given name), a given name in English Surname * Chinese surnames romanized as Li or Lee: ** Li (surname 李) or Lee (Hanzi ), a common Chinese surname ** Li (surname 利) or Lee (Hanzi ), a Chinese ...
, p. 271


315

For 1956, Dodge increased the displacement to with a longer stroke and a taller raised-deck block and now with a polyspheric heads—no longer a Hemi. But the optional high-performance D-500 version of this engine had a four-barrel carburetor and a larger valved Dodge hemispherical combustion chambered head. Also, a "race only" package called the D-500-1 or DASH 1 was available with a special aluminum dual four-barrel intake that sported a pair of Carter WCFB carburetors similar to the ones on the Chrysler 300B and DeSoto Adventurer. This engine used the same cylinder heads as the base D-500 model. The D-501 in 57 was the Chrysler 354 engine, not a Dodge-based engine.


325

Dodge released a engine for 1957. The "Super Red Ram" engine used a bore and stroke. The base engine offering was now a polyspheric chambered head referenced as 'KDS', and a higher performance 325 was offered with hemi heads as the 'KD-500'. Again there was a low volume offering of a 'KD-500-1' with dual four-barrel carburetors. All engines now, however, had hydraulic camshafts even though the hemi headed offerings sported "dimples" in the valve covers for mechanical adjuster clearance.


Second generation: 426

The hemispherical head design was revived in 1964. These were the first engines officially designated Hemi, a name
Chrysler Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automotiv ...
had trademarked. Chrysler Hemi engines of this generation displaced . The 426 Hemi was nicknamed the "elephant engine" at the time, a reference to its high power, heavy weight and large physical dimensions. Its deck height and bore spacing made it the biggest engine in racing at the time. The 426 Hemi of the 1960s was an engine produced for use in
NASCAR The National Association for Stock Car Auto Racing, LLC (NASCAR) is an American auto racing sanctioning and operating company that is best known for stock car racing. The privately owned company was founded by Bill France Sr. in 1948, and ...
, as raced in a
Plymouth Belvedere Plymouth Belvedere is a series of American automobile models made by Plymouth from 1954 until 1970. The Belvedere name was first used for a new hardtop body style in the Plymouth Cranbrook line for the 1951 model year. In 1954 the Belvedere r ...
in 1964. It was not initially available to the general buying public. The 426 Hemi was not allowed to compete in NASCAR's 1965 season due to its unavailability in production vehicles sold to the general public and because of complaints by Ford regarding its power. However several special production versions of the Dodge Dart, the Plymouth Fury, and later, in 1965, the Dodge Coronet, were produced with aluminum fenders and bumpers for
drag racing Drag racing is a type of motor racing in which automobiles or motorcycles compete, usually two at a time, to be first to cross a set finish line. The race follows a short, straight course from a standing start over a measured distance, most ...
and made available to the general public. Chrysler introduced the "Street" Hemi in 1966 for its intermediate range of cars and sold the required number of Hemi engines to the public to homologate its use for stock car racing in NASCAR events in 1966. The "Street Hemi" was similar to the race Hemi but with an inline 2X4-bbl induction system (with automatic choke), lower compression (10.25:1 from 12.5:1) and lower-lift
camshaft A camshaft is a shaft that contains a row of pointed cams, in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition systems ...
, with iron exhaust manifolds instead of lighter steel long tube headers. There were many differences between the Hemi and the Wedge-head big-block, including main
cross-bolted bearing A cross-bolted bearing is a bearing, usually a crankshaft main bearing of a piston engine. Most bearing caps are retained by two bolts, one on each side of the bearing journal, and parallel to the cylinder axis (or, on vee engines, parallel to an a ...
caps and a different head bolt pattern. Although all manufacturers were familiar with
multi-valve In automotive engineering a multi-valve or multivalve engine is one where each cylinder has more than two valves. A multi-valve engine has better breathing and may be able to operate at higher revolutions per minute (RPM) than a two-valve engi ...
engines and hemispherical combustion chambers, adding more valves per
cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an ...
and designing the complex
valvetrain A valvetrain or valve train is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine. The intake valves control the flow of air/fuel mixture (or air alone for direct-injected engines) ...
they require were expensive ways of improving the high– revolutions per minute (rpm) breathing of production vehicles. By canting the angle of the NASCAR-mandated two valves per cylinder, significantly larger valves could be used. The Chrysler 426 Hemi and all Chrysler RBs had oversquare bore and strokes. Specifically, the 426 Hemi and 426 Wedge had a bore x
stroke A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorr ...
of . The 426 Hemi, in "street Hemi" form, was produced for consumer automobiles from 1965 through 1971. Hemi-powered Dodge and Plymouth cars produced in the model years of 1965 through 1971 have become collector's items. For example, a 1971 Plymouth Barracuda Convertible equipped with the 426 Hemi engine sold at auction for US$3.5 million in 2014. The street Hemi version was rated at at 5000 rpm SAE gross and at 4000 rpm of torque equipped with a pair of four-barrel Carter AFB carburetors. In actual dynamometer testing, it produced and of torque in purely stock form. Chrysler's sales literature published both the gross and net ratings for 1971. The street version of the 2G Hemi engine was used (optionally, in all but the last case) in the following vehicles: * 1966–1970 Dodge Coronet/
Plymouth Belvedere Plymouth Belvedere is a series of American automobile models made by Plymouth from 1954 until 1970. The Belvedere name was first used for a new hardtop body style in the Plymouth Cranbrook line for the 1951 model year. In 1954 the Belvedere r ...
* 1966–1971 Plymouth Satellite * 1966–1971
Dodge Charger The Dodge Charger is a model of automobile marketed by Dodge in various forms over seven generations since 1966. The first Charger was a show car in 1964. A 1965 Charger II concept car resembled the 1966 production version. The Charger has ...
* 1966-1971 Jensen FF * 1966-1971 Jensen Interceptor * 1967–1971 Plymouth GTX * 1968 Dodge Dart Super Stock * 1968
Plymouth Barracuda The Plymouth Barracuda is a two-door pony car that was manufactured by Plymouth from 1964 to 1974. The first-generation Barracuda was based on the Chrysler A-body and was offered from 1964 to 1966. A two-door hardtop (no B-pillar) fastback de ...
* 1968–1971 Dodge Super Bee * 1968–1971 Plymouth Road Runner *1969 Dodge Charger R/T * 1969 Dodge Charger Daytona * 1970 Plymouth Superbird * 1970–1971 Plymouth Hemi 'Cuda * 1970–1971
Dodge Challenger The Dodge Challenger is the name of three different generations of automobiles (two of those being pony cars) produced by American automobile manufacturer Dodge. However, the first use of the Challenger name by Dodge was in 1959 for marketing ...
* 1970
Monteverdi Hai 450 The Monteverdi Hai 450 SS was a mid-engined prototype, an attempt to create a full sports car complementing the company's High Speed line. It was intended to be a direct competitor to the top of the list super sports cars of Lamborghini, Ferrari ...
To avoid confusion with earlier (1951–58) and current Hemi engines, the 426 is sometimes called the "2G" or "Gen 2" Hemi.


In racing

There were many differences between the racing Hemis and the street Hemi, including but not limited to
compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stati ...
, camshaft, intake manifold,
exhaust manifold In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. The word '' manifold'' comes from the Old English word ''manigfeald'' (from the Anglo-Saxon ''manig'' anyand ''feald'' old and ref ...
. Some 1960s NASCAR and NHRA Hemi engines featured magnesium cross-ram intake manifolds and magnesium oil pans in an attempt to reduce the massive weight of the overall engine, along with chain-driven internal dry sump oil systems. Today, aftermarket blocks, heads, intakes, rods, and
piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-t ...
s are usually made of aluminum. The 426 Hemi also was used in NHRA and AHRA drag racing. Its large
casting Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a ''casting'', which is ejecte ...
allowed the engine to be overbored and stroked to displacements unattainable in the other engines of the day. Top-fuel racing organizers limited the bore spacing of engines until very recently, when under pressure from Ford and other manufacturers, the bore spacing allowed was increased to —this allows other engines such as the Ford 385 series to begin to compete. The engines based on the old Chrysler design predominate Top Fuel and
Funny Car Funny Car is a type of drag racing vehicle and a specific racing class in organized drag racing. Funny cars are characterized by having tilt-up fiberglass or carbon fiber automotive bodies over a custom-fabricated chassis, giving them an appea ...
classes due to plentiful parts, a large amount of research and development, as well as decades of experience with the problems of the engine's design. In drag racing today, it is usually equipped with a large
Roots type supercharger The Roots-type blower is a positive displacement lobe pump which operates by pumping a fluid with a pair of meshing lobes resembling a set of stretched gears. Fluid is trapped in pockets surrounding the lobes and carried from the intake si ...
and short individual exhaust pipes, and fueled with nitromethane. Yet, this variant is used in Top Fuel, Funny Car, and Pro Modified classes.


Third generation: 2003-present

The current-production "HEMI" engine heads are flatter and more complex than the 1950s–'70s Hemi V8 chamber. The combustion chambers are no longer truly hemispherical. It uses a coil-on-plug distributor-less ignition system and two spark plugs per cylinder to shorten flame travel leading to more consistent combustion and reduced emissions. Like most of Chrysler's past-model Hemi-head engines, the 5.7 version is rated at approximately one horsepower per cubic inch (the current engines are SAE net, whereas the old Hemi engines were rated SAE gross). For the 2009 model year power was increased to 357-395 horsepower (266-291 kW) and 389-410 lb·ft (527-556 N·m) depending on application. It also achieved 4% better fuel economy. Variable valve timing (VVT) was also introduced. A new
variable displacement Variable displacement is an automobile engine technology that allows the engine displacement to change, usually by deactivating cylinders, for improved fuel economy. The technology is primarily used in large, multi-cylinder engines. Many automob ...
technology called Multi-Displacement System (MDS) is used in some versions which can shut off two cylinders on each bank under light load to improve fuel economy.


5.7

The 5.7 L HEMI was released for model year 2003 on the Dodge Ram
pickup truck A pickup truck or pickup is a light-duty truck that has an enclosed cabin, and a back end made up of a cargo bed that is enclosed by three low walls with no roof (this cargo bed back end sometimes consists of a tailgate and removable covering) ...
s to complement the Magnum 5.9 engine. it was the only available gasoline engine in the Ram Heavy Duty. Chrysler later made the 5.7 L Hemi available in all models of the 2004 Dodge Ram,
Dodge Durango The Dodge Durango is a mid-size sport utility vehicle (SUV) produced by Dodge in three generations starting with the 1998 model year. The first two generations were very similar in that both were based on the Dodge Dakota and Ram Pickup, both fe ...
, the 2005
Chrysler 300C The Chrysler Corporation has used the designation Chrysler 300C to refer to two separate unrelated vehicles from different eras: * The 1957 Chrysler 300C is that year's version of the Chrysler 300 "letter series"; a large, high-performance luxury ...
, Dodge Magnum R/T, Jeep Grand Cherokee, the 2006 Dodge Charger R/T, Jeep Commander, the 2007 Chrysler Aspen, the 2009
Dodge Challenger The Dodge Challenger is the name of three different generations of automobiles (two of those being pony cars) produced by American automobile manufacturer Dodge. However, the first use of the Challenger name by Dodge was in 1959 for marketing ...
R/T, and the 2022 Jeep Wagoneer. For manual transmission applications (Challenger and 3/4- and 1-ton Ram pickups), cylinder deactivation is not included. The Hemi in the Ram delivered and , but and for the 300C and Magnum R/T, which is exactly more than the old 5.9 engine. It is a 90-degree V8, 2-valve
pushrod A valvetrain or valve train is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine. The intake valves control the flow of air/fuel mixture (or air alone for direct-injected engines) ...
design like the past Magnum series engines, displacing , with a bore of and a stroke of . The 5.7 L Hemi is made at Chrysler's
Saltillo Engine Saltillo Engine is a Chrysler engine plant in Ramos Arizpe, Coahuila, Mexico. The factory opened in 1981. It was built as a scale model of the plant at Trenton, Michigan, United States, but with more work flexibility, having only 20 job classificat ...
plant in Ramos Arizpe, Mexico. The Hemi was on the Ward's 10 Best Engines list for 2003 through 2007, and again in 2009. This engine is used in the following vehicles: * 2003–present Ram Pickup * 2004–2009, 2011–Present
Dodge Durango The Dodge Durango is a mid-size sport utility vehicle (SUV) produced by Dodge in three generations starting with the 1998 model year. The first two generations were very similar in that both were based on the Dodge Dakota and Ram Pickup, both fe ...
* 2005–2008
Dodge Magnum The Dodge Magnum is a nameplate used by several Dodge vehicles, at different times and on various markets. The name was first applied to a large Chrysler B platform-based 2-door coupe marketed from 1978 to 1979 sold in the United States and Canad ...
''R/T'' * 2005–present Chrysler 300C, 300S V8 (2010, 2012–Present) * 2005–present Jeep Grand Cherokee * 2006–present
Dodge Charger The Dodge Charger is a model of automobile marketed by Dodge in various forms over seven generations since 1966. The first Charger was a show car in 1964. A 1965 Charger II concept car resembled the 1966 production version. The Charger has ...
''R/T'' * 2006–2010 Jeep Commander * 2007–2009 Chrysler Aspen * 2009–present
Dodge Challenger The Dodge Challenger is the name of three different generations of automobiles (two of those being pony cars) produced by American automobile manufacturer Dodge. However, the first use of the Challenger name by Dodge was in 1959 for marketing ...
''R/T'' * 2022–present Jeep Wagoneer


2009 5.7 revisions

Chrysler made various revisions to the 5.7 L for the 2009 model year. The first for all applications is what Chrysler calls Variable Camshaft Timing or VCT. VCT (which is essentially
variable valve timing In internal combustion engines, variable valve timing (VVT) is the process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions. It is increasingly being used in combination with var ...
) uses an oil control valve that controls oil flow to a unique camshaft sprocket that contains a phasing device, which depending on the operation of the oil control valve either advances or retards camshaft timing. Cylinder heads have been revised to increase flow. Though the intake manifold has also been changed on all applications, it is however model specific. Dodge Ram, non-Hybrid Electric Vehicle (HEV) Chrysler Aspens, and non-HEV Dodge Durango utilize an active intake manifold with a short runner valve to optimize torque and horsepower. At lower engine rpm the valve is closed, resulting in improved low-end torque from the longer runners. At higher engine rpm the valve is opened, diverting the incoming air into the center of the manifold. The shorter runners result in improved horsepower. Passenger cars, Jeep vehicles, as well as HEV Chrysler Aspen and HEV Dodge Durango do not use this manifold; instead, these vehicles utilize a passive intake manifold, which does not have a short runner valve. Also, the new cylinder head came with different spark plugs seats: tapered seats was replaced with gasket seats. This change made it impossible to use the old OE Champion RE14MCC4, so the new spark plugs that came with 5.7 HEMI become NGK LZFR5C-11. Besides different seats, new spark plugs got increased gap from .039" (1.0 mm) to .043" (1.1 mm). Six-speed manual transmission and all Heavy Duty truck applications will differ by not having the Multi-Displacement System (MDS). The new version of the 5.7 L has five different camshaft profiles. All will have VCT. * Active intake with MDS * Active intake without MDS * Passive intake with MDS * Passive intake without MDS * HEV Application (modified version of passive intake with MDS) Power Numbers * 300C/300S V8: , * Charger R/T: , * Challenger R/T Automatic: , * Challenger R/T 6 Speed Manual: , * 2009-2012 Ram 1500 Truck: , * 2013+ Ram 1500 Truck: , * Ram 2500/3500 Truck: , * Jeep Grand Cherokee and Jeep Commander: , * 2011+ Dodge Durango: , * 2009 Chrysler Aspen and Dodge Durango non-HEV: , * 2009 Chrysler Aspen and Dodge Durango HEV: , * 2022 Jeep Wagoneer: ,


6.1

The Hemi is also available in a version. The engine's bore x
stroke A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorr ...
is and many other changes were made to allow it to produce at 6,200 rpm and of torque at 4,800 rpm. The engine block is different from the 5.7, with revised coolant channels and oil jets to cool the pistons. A forged
crankshaft A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecti ...
, lighter pistons and strengthened
connecting rod A connecting rod, also called a 'con rod', is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the crank ...
s aid durability. A cast aluminium intake manifold is tuned for high-rpm power and does not include variable-length technology.
Chrysler Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automotiv ...
's Multi-Displacement System is not used on the 6.1. Applications: * 2005–2010 Chrysler 300C ''SRT-8'' * 2006–2008
Dodge Magnum The Dodge Magnum is a nameplate used by several Dodge vehicles, at different times and on various markets. The name was first applied to a large Chrysler B platform-based 2-door coupe marketed from 1978 to 1979 sold in the United States and Canad ...
''SRT-8'' * 2006–2010
Dodge Charger The Dodge Charger is a model of automobile marketed by Dodge in various forms over seven generations since 1966. The first Charger was a show car in 1964. A 1965 Charger II concept car resembled the 1966 production version. The Charger has ...
''SRT-8'' * 2006–2010 Jeep Grand Cherokee ''SRT-8'' * 2008–2010
Dodge Challenger The Dodge Challenger is the name of three different generations of automobiles (two of those being pony cars) produced by American automobile manufacturer Dodge. However, the first use of the Challenger name by Dodge was in 1959 for marketing ...
''SRT-8''


6.2 Hellcat

For 2015, Chrysler introduced an all-new high performance supercharged variant of the Hemi engine, called the Hellcat (named after the Grumman F6F Hellcat). It features the same bore as the 6.4 L Hemi and the same stroke as the 5.7 L, giving it a total displacement of . The supercharger is a twin-screw
IHI Ihi, Ehee (Nepal Bhasa:ईही) is a ceremony in the Newar community in Nepal in which pre-adolescent girls are "married" to the Suvarna Kumar which is a symbol of the god Vishnu, ensuring that the girl becomes and remains fertile. It is beli ...
unit with integrated
charge cooler An intercooler is a heat exchanger used to cool a gas after compression. Often found in turbocharged engines, intercoolers are also used in air compressors, air conditioners, refrigeration and gas turbines. Internal combustion engines Most ...
s, capable of producing of boost. This engine is rated at at 6,000 rpm and at 4,000 rpm of torque and has a
compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stati ...
of 9.5:1. This engine was the most powerful engine produced by
Chrysler Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automotiv ...
as well as the most powerful production engine ever in a
muscle car Muscle car is a description according to '' Merriam-Webster Dictionary'' that came to use in 1966 for "a group of American-made two-door sports coupes with powerful engines designed for high-performance driving." The '' Britannica Dictionary'' ...
until the Dodge Demon was introduced. This engine is not equipped with Chrysler's Multi-Displacement System. In 2017, Mopar announced that it would sell it as a crate engine under the name Hellcrate. A Redeye version with debuted in the Dodge Challenger in 2019, followed by the Dodge Charger in 2021. Applications: * 2015–Present Dodge Challenger SRT Hellcat * 2015–Present Dodge Charger SRT Hellcat * 2018–present Jeep Grand Cherokee Trackhawk * 2021 Dodge Durango SRT Hellcat * 2017 Ram 1500 Rebel TRX Concept * 2021–Present Ram 1500 TRX


6.2 Demon

The Demon version of the Hemi V8 features a number of improvements over the Hellcat variant. It is fitted with a larger, 2.7 L twin-screw supercharger, as well as reinforced reciprocating components, a new camshaft, and several other valvetrain upgrades. With these improvements, the Challenger SRT Demon is rated at 808 horsepower on 91-octane pump gasoline, and 840 horsepower when running on 100-octane unleaded racing gasoline. Cooling is aided by a functional Air-Grabber hood scoop, as well as a unique charge cooling system that makes use of the air-conditioning coolant to lower the intake charge air temperature. Applications: * 2018 Dodge Challenger SRT Demon


6.4

Chrysler displayed a larger and more powerful 392-cubic-inch (6.4 L) HEMI in 2005 with a factory-rated output of and torque. It is equipped with high-strength forged aluminum alloy pistons. This engine has been available since 2007, as a crate engine under the name 392 HEMI. The production version of the 392 HEMI was launched in the 2011 Dodge Challenger SRT8 with variable camshaft timing as well as MDS in cars with automatic transmissions. The new 392 HEMI, codenamed "Apache," is based on the third-generation 5.7 L HEMI, codenamed "Eagle," and shares few parts with the 392 crate engine. Special-Edition Chargers and Challengers equipped with this engine, and the engines themselves, will bear "392 HEMI" badging in commemorative reference to the first-generation engine of the same displacement. In other applications, the engine is badged as "6.4L HEMI". Output is and ; For the 2015 model year, horsepower was increased to and torque to in the Charger and Challenger ''SRT 392'' (2015-2018) and ''R/T Scat Pack'' (2015–present) models; the Grand Cherokee SRT only saw a 5 bhp increase. Export models of the Chrysler 300 SRT retained the and output. Applications: * Chrysler 300 SRT * Dodge Challenger SRT 392 * Dodge Charger SRT 392 * Dodge Durango SRT * Jeep Grand Cherokee SRT * Jeep Grand Wagoneer * Jeep Wrangler Unlimited Rubicon 392


HD Truck and Cab Chassis version

Starting in model year 2014, the Ram 2500 and 3500 trucks, and Ram 3500, 4500, and 5500 Cab Chassis offered a revised version of the 6.4 L, being re-tuned for better fuel economy and a power band more suitable for hauling and towing than the all-out power of the SRT Version. In 2016 it replaced the 5.7 L as the standard gas engine in the Cab Chassis models. Power Numbers * 2500 and 3500 Pickup, 3500 SRW Cab Chassis with RFE transmission: , * 3500 Mega Cab, 3500 DRW Cab Chassis with RFE transmission, 3500 SRW/DRW with Aisin Transmission: , * 4500 and 5500 Cab Chassis: ,


Mopar 426 HEMI (2012–present)

At the 2012 North American International Auto Show in Detroit, Dodge debuted a Mopar Customized Dodge Charger "Redline" that featured a modern 426-cubic-inch (7.0 L) HEMI V8 engine rated at .


Mopar 426 HEMI 'Hellephant' (2018-present)

The Hellephant name is a spin on the nickname of the original 426 cubic inch HEMI, Elephant, and the modern Supercharged 6.2L Hellcat HEMIs. It is a crate engine, supercharged as standard, producing 1,000hp and 950lb.-ft of torque.


Marketing

From February to April 2005, DaimlerChrysler hosted a "What Can You HEMI?" contest promoting alternative uses of the HEMI engines. The top five finalists include HEMI Snowblower, HEMI-Go-Round carousel, HEMI on Ice ice resurfacer, HEMI-Shredder, HEMI Big Wheel, i.e. the child's tricycle of the 1970s. The winner was the HEMI Big Wheel, which had a 5.7 L Hemi in the back that was installed backwards, thus reverse became the only forward gear. Plate steel was the predominant material, while a rolled tube of steel had to be utilized for the front tire as there were no such tires in diameter that were as narrow as needed for this project.


Notes


References


External links


How a hemi engine works

A Body Hemi engine swaps





Mopar HEMI Gen II page

Mopar HEMI Gen III page
{{DEFAULTSORT:Chrysler Hemi Engine
Hemi Hemi may refer to: People Surname * Jack Hemi (1914–1996), New Zealand freezing worker, rugby union and league player, shearer * Ronald Hemi (1933–2000), New Zealand rugby union player Given name * Hemi Bawa, Indian painter and sculptor * ...
V8 engines