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The new Hemi Magnum (as though the Hemi name couldn't stand on its own!) produces 345 horsepower (5,600 rpm) and 375 lb-ft of torque (4,400 rpm) from 5.7 liters (345 cid*) - one horsepower per cubic inch, and it is still the engine's first year. In addition to truck duty, it will be used in the new LX series, in front of a Mercedes five-speed automatic. The Hemi is smaller, faster, and more economical (we hear also cheaper to build) than the 360 it is replacing.

Hemi production began in June 2002 at the Salitillo plant in Mexico, with a projected production of 440,000 engines a year. Only about a quarter of those engines will be used in heavy duty pickups, with the rest expected to end up in Grand Cherokees, large cars, Dakotas, Durangos, and light duty pickups.

The original Hemi was actually smaller than this one, but the most famous, the unbeatable 426 Hemi, was considerably larger - and produced quite a bit more power, albeit before emissions standards. That engine took first, second and third place at the 1964 Daytona 500 and became the de facto drag racing standard, not to mention the killer street engine - one which added about a third again to the price of a new car. It re-entered production for racing recently.

The engine's unique two-valve hemispherical combustion chamber within an aluminum head provides impressive air flow, torque and power (hallmarks of the original), and gives the engine its throaty rumble. Fifty-six pounds lighter than the 5.9-liter V-8, the 5.7-liter HEMI produces 41% more power and a 12% increase in peak torque. "The HEMI architecture produces power that is comparable to an overhead cam engine, but is more cost-effective," according to Floyd Allen, Vice President - Powertrain Product Team.

An electronic throttle control system, Chrysler's first drive-by-wire gasoline engine, moves the throttle in response to accelerator pedal position. The throttle system is based on engine torque control, and compensates for changes in the engine load needed by the air conditioning system, compressor, alternator, power steering pump and automatic speed control.

Dual spark plugs per cylinder ensure consistent, complete and rapid combustion, without knock, that increases peak power and torque, reduces exhaust emissions and increases fuel efficiency. It even smoothes the engine's idle. The 5.7-liter HEMI also meets all federal emissions standards and delivers an 8-10 percent improvement in fuel efficiency under typical driving conditions compared with the engine it replaces.

Testing included 11 million customer equivalent miles, with stronger durability testing than any previous Chrysler engine. The 5.7-liter HEMI's 7 year/70,000-mile powertrain warranty is backed by an impressive 11 million customer equivalent miles (CEMs) of testing, including more than 200,000 CEMs of durability testing for the average consumer - more than any other Chrysler Group engine. The battery of reliability tests closely represents real-world driving conditions, in some cases exposing the engine to more severe abuses than drivers can dish out. For example, during a 260-hour period, the 5.7-liter HEMI was repeatedly heated to 240°F and then slammed with coolant that was -25°F.
"The engine was exposed to some of the harshest testing conditions and abuses imaginable," said Donald Dees, Vice President of Quality for the Chrysler Group (and formerly of Toyota, so you know that means something).
Cylinder deactivation, which shuts off fuel to some cylinders under idle and low demand situations, is expected in 2004. That will increase fuel economy.
The new Hemi features cross-flow aluminum cylinder heads with hemispherical combustion chambers and cast, steel rocker arm actuated splayed valves for high air flow; two spark plugs per cylinder for fast, efficient combustion; and a new direct ignition system with high-power coils ensuring consistent, complete combustion.

A fully-balanced, cast, nodular iron crankshaft running in cross-bolted steel main bearing caps reduces deflection and vibration for better drivability.

Floyd Allen, Vice President, Product Powertrain Team, said: "The new 5.7-Liter HEMI Magnum utilizes such advances as a composite integrated air fuel module and electronic throttle control. The hemispherical head design allows the use of larger valves and provides better air flow to the combustion chambers."

*Different Dodge listings mention 345, 354, and even 353 cubic inches as the engine size; since it is a 5.7, the actual number is up for grabs, but 345=5.65 liters and 354=5.8 liters. 353=5.78 liters...(the Dodge customer site says 353, Dodge PR said 345 but now says 354). The bore is 3.92", the stroke 3.58", and Ryan McNamara pointed out that this adds up to 345.6 cubic inches - let's say 345 and have a definitive answer.

It has 16 pushrod-operated overhead valves, hydraulic lifters with roller followers, sequential multiple-port returnless fuel injection, and a compression ratio of 9.6:1. It uses a deep-skirt cast iron block with cross-bolted main bearing caps, and aluminum alloy heads with of course hemispherical combustion chambers. In this regard, it is similar to the V10 (based on the venerable LA V8s), which also has a deep skirt cast iron block, hydraulic lifters with roller followers, and pushrod-operated overhead valves - two per cylinder. (The V10 has iron heads when used in trucks.)

The Hemi was subjected to a rigorous reliability program, accumulating more than 7.5 million customer equivalent miles.

Dual spark plugs are used to speed fuel combustion, making the engine more powerful and efficient while decreasing emissions (though not down to ULEV levels). A cylinder deactivation system, which does not appear to be related to systems used by Mercedes, was originally designed into the engine to prevent fuel from being wasted when the engine is under light loads. We don't know whether this was continued, because it is not mentioned in any of Dodge's current publicity materials. (Thanks, Troy Kleffman.)

AI-Online also noted that the Hemi has double rocker shafts in each head, like its predecessors, but has valve gear within the head walls.

Like the original Hemi, it will produce one horsepower per cubic inch. To be fair, this level of power is no longer rare - for example, the Dodge Neon 2.0 liter engine, with 122 cubic inches, produces 133 horsepower and 129 lb-ft of torque. However, it is unusual in truck V8s. The 4.7, for example, with 287 cubic inches, produces 235 horsepower.
The 5.7, like its LA predecessors, has a cast iron cylinder block; however, it weighs less and is smaller than the 5.9. It was designed with a single in-block camshaft and only two valves per cylinder, resulting in very low production costs; development and production costs, in fact, are supposed to be less than the new 4.7 liter Mopar V8 which in turn was considerably cheaper to produce than the old LA 318.

The two-valve-per-cylinder design means not only lower production costs, but also better low-end torque, which is a good selling point considering the high-revving nature of most current generation engines.

The Hemi is designed for trucks, but most likely will be used in large sedans with rear wheel drive.

The Hemi will be built in Saltillo, Mexico, starting at 300,000 units per year but possibly rising. A 383 cid version has been rumored, on and off. The 383 size would strike a chord in the enthusiast community.

Specfications (in the 2003 Ram 2500)Type and Description: Eight cylinders, 90° V-type, liquid-cooled
Valve System: Pushrod-operated overhead valves, 16 valves, hydraulic lifters with roller followers
Fuel Injection: Sequential, multi-port, electronic, returnless
Construction: Deep-skirt cast iron block with cross-bolted main bearing caps, aluminum alloy heads with hemispherical combustion chambers
Compression Ratio: 9.6:1

Revised specifications - note greater power!Specifications are for the engine in the 2500 trucks.

Power (SAE net): 345 bhp (257 kW) @ 5,400 rpm
Torque (SAE Net): 375 lb.-ft. (508 Nom) @ 4,200 rpm

Displacement 354 cu. in (5,654 cu. cm)
Bore x stroke 3.92 x 3.58 (99.5 x 90.9)
Valve system Pushrod-operated overhead valves, 16 valves, hydraulic lifters with roller followers
Fuel injection Sequential, multi-port, electronic, returnless
Construction Deep-skirt cast iron block with cross-bolted main bearing caps. Aluminum alloy heads with hemispherical combustion chambers
Max. engine speed 5,800 rpm
Fuel requirement Unleaded mid-grade, 89 octane (R+M)/2 - recommended, Unleaded regular, 87 octane (R+M)/2 - acceptable

Oil capacity 7 qt. (6.6L)
Coolant capacity 18.7 qt. (17.7L)
Engine Weight 590 lbs.
Width 27”
Lenght 26” (Balancer to Bell Housing)