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Modern Mopar / Chrysler / Dodge 5.7 Hemi Magnum V8 Engines

Hellcat: Supercharged 6.2 Hemi6.4 Truck HemiSRT Hemis426 HemiHemi History

horsepower and torqueThe first-generation 5.7 liter “new Hemi” produced up to 350 horsepower at 5,600 rpm and 375 lb-ft of torque (4,400 rpm) — one horsepower per cubic inch.

The second generation rose to 390 horsepower and 407 lb-ft of torque in the Dodge Ram — 375 horsepower in the 2009 Dodge Challenger with manual transmission; power varied by car or truck.

SRT Hemi engines started with the 6.1 Hemi, with 425 horsepower at 6,000 rpm (matching the 426 Hemi’s number) and, in 2014, the supercharged 6.2 Hemi went to 707 horsepower in 2014.

A 6.4 liter non-SRT Hemi V8 in the 2014 heavy duty Rams was designed for durability, torque, and economy with heavy loads.

Updates to the 5.7 “Eagle” Hemi and 6.4 “Apache” Hemi might be coming; these were rumored to boost horsepower and torque, and to include direct injection, which is slated for the Pentastar V6 in 2017-18.

5.7 G1 G1 G2 G2 G2.1
As used in...RamCharger2007 RamChallengerChallenger
Horsepower 345 @ 5,600 340 @ 5,000 390 375 @ 5,800 379
Torque 375 @ 4,400 390 @ 4,000 407 398 @ 4,200 410
EPA mpg 13/17 15/23 13/19 16/25 17/25

General Hemi engine information

Chrysler's 5.7 Hemi engineThe Hemi was smaller, more powerful, and cheaper to build than the LA-series 360 V8 and “Next Generation” 4.7 liter V8 it replaced, but produced more power and torque. It has been hooked up to the Mercedes five-speed automatic, Chrysler’s five and six speed truck transmissions, and the ZF eight-speed.

The cast iron block has a “meaty” deep-skirt design, and the crankshaft is supported by four bolts per main bearing (two vertical, two horizontal). The heads are aluminum and the intake manifold is plastic (for light weight and high flow).

Code names, based on planes:
5.7 = Eagle; 6.4 = Apache; 6.2 = HellCat

Tom Hoover, “father of the 426 Hemi,” told Hot Rod that he had discussed the Elephant Engine’s design with new-Hemi engineers. Three of his major suggestions — raising the camshaft (to shorten the pushrods, reducing valve-train inertia and simplifying the rocker arms), using twin spark plugs, and adding squish area (for more light load/low speed efficiency and reduced emissions) were adopted.

The Hemi V8 has been immensely popular. In 2005, Hemi engine take rates was around 45% on cars and trucks where it was an option. Retired tuning chief Pete Hagenbuch commented that it was the most successful Hemi ever, because it could be built at a profit.

HEMI engine - variable cam

2009: Hemi 5.7 Liter V8 Engine Revisions

5.7 liter Hemi V8 engine cutawayThe 2009 Hemi was extensively modified to increase both power and gas mileage; it included a higher compression ratio, better-flowing heads, intake, and exhaust, and an active intake manifold. The active intake, previously used on the 3.5 liter V6, takes advantage of Chrysler advances in the 1960s; it switches from long runners to short runners by moving a flapper door, to switch from better torque at low engine speeds to higher horsepower as rpms rise.

The new variable valve timing system used hydraulic cam phasing, relatively simple and inexpensive. The hydraulic roller camshaft had oil passages in front to drive the cam phaser sprocket, and increase valve lift. A new piston/rod assembly had thinner walls with a stronger-alloy pin.

Dodge hemi engine with MDS system

The ports were redesigned, with a raised exhaust floor; new intake valves were 2mm larger. Other upgrades were a stronger crankshaft, dual-mass crankshaft damper, floating pin pistons, new valve springs, and higher oil pump capacity. The results were better reliability and gas mileage, with more horsepower and torque at every point in the engine’s speed range. oh2o had predicted variable cam timing in mid-2007. Redriderbob correctly predicted an updated MDS system in May 2007.

Dual spark plugs

Michael E. Gemmel wrote: “Each cylinder has an ignition coil pack over one spark plug, and a regular plug wire connected to the other spark plug. Further, the coil pack also has a plug wire attached to it that extends to the opposite cylinder bank. Each cylinder shares a coil pack with another cylinder. Each of the two plugs on a given cylinder is fired by a separate coil. One plug has a coil directly attached, and the other is fired via an ignition wire connected to a coil located on another cylinder on the opposite bank. The benefits would be one-half the number of coils (8 vs. 16) compared to each plug having its own coil, and of course less weight.”

Closeup of Chrysler MDS system

“Cryptojoe” wrote: “The extra plug fires during the power stroke to more fully burn the hydrocarbons. ... the second ignition allows additional power in the down stroke while lowering the need for restrictive catalyst plates in the converter. ... [using] dual fired plugs on each cylinder allows the firing to take place closer to top dead center, and then again when the piston is on the back side of the power stroke.”

Patrick added: “The extra set of spark plugs on the HEMI and on previous engines are designed to reduce NOx and ozone emissions before a catalyst is needed. They add some horsepower, but not much.”

Displacement on demand: cylinder deactivation

The cylinder deactivation or “Multi Displacement System” (MDS) turns off the fuel in four cylinders when power is not needed. Chrysler said that the MDS system saved nearly 100 million gallons of gasoline between 2005 and 2009, and reduced carbon dioxide (CO₂) emissions by close to a million metric tons. Cylinder deactivation first appeared in cars, and was added to Ram Hemis later.

truck hemi

The 2005 Chrysler 300C and Dodge Magnum RT were the first high-volume, modern production vehicles in North America to use cylinder deactivation (though GM was the first to use such a system with the failed Cadillac “four-six-eight” system). Bob Lee, Powertrain Product Team vice president, said, “The MDS was part of the engine's original design. This resulted in a cylinder-deactivation system that is elegantly simple and completely integrated into the engine design. The benefits are fewer parts, maximum reliability and lower cost.”

hemi cutaway

The first-generation Hemi could transition from eight cylinders to four in 0.04 seconds by keeping the valves in four cylinders closed. While some energy is lost through compression, none is lost by pumping air through them. The system raised fuel economy by around 10% overall. Because (as with the slant six) oil comes through the pushrods, the engine was still fully lubricated.

Chhemi badgerysler engineer Cole added: “The modern Hemi always shuts off the same four cylinders. In our durability test cycle (150,000 customer equivalent miles driven at the 95th percentile, meaning that only 5% of our owners are more abusive than our testing), we have not found any adverse wear patterns.”

Specific Hemi advantages (written about the first generation)

The source for most of this information is Popular Hot Rodding.

The hollow cam has oversized journals and lobes to reduce side loading on the lifters; roller-style lifters reduce friction and wear. The valve springs are beehive types, more effective than standard springs, so they can be lighter, with less lifter collapse. Rockers are light, and their flow is enough to compensate for their conservative .500 inches of lift.

The new Hemi is precision cast, which allows it to be lighter than a typical 5.7 liter engine, even with a taller deck height than GM’s equivalent V8; the slipper-style pistons are light (413g), using cast eutectic alloy. For longevity, the Hemi pistons are anodized on the top ring, which works as a combined heat barrier and anti-micro-weld mix, and allows the top ring to be only 3 mm from the top of the piston. As with the 426 Hemi, the rings are thin; a reservoir groove underneath the top ring cuts the pressure between the top and second ring. The skirt is coated to increase the fit range for ring seals and reduce noise.

The crank has larger inner counterweights than similar (2007) GM engines, but their weight is offset by the lighter pistons and rods. A windage tray under the crank makes sure oil is always available, and the serpentine belt pulley acts as a torsional vibration damper. Connecting rods are strong and light enough to eliminate the need for a balance pad.

chrysler hemi engine

As usual, Chrysler used a speed density system instead of a mass airflow sensor (the 6.2 uses a MAF instead, though).

The two-inch ports flow 270 cfm at .600 inches of lift, with peak flow at .375 inches, and good flow even at .250 inches of lift. The exhaust port hits 161 cfm at .600 lift, with a 1.55 inch valve. Both have good velocity and distribution throughout their range, compared with a contemporary GM LS6 engine.

General hemi engine notes

Hemi production began in June 2002 at the Saltillo plant in Mexico; the first supercharged Hemi engine officially produced by Chrysler was shown to the public in January 2003, pumping out 430 horsepower and 480 lb-ft of torque, using the 5.7 Hemi engine and a Whipple supercharger (in the Dodge Magnum SRT-8 concept). The 300C version had “over 400 horsepower” and 350 lb-ft of torque.

hemi engine valves

The famed 426 Hemi had powered the first, second and third place winners at the 1964 Daytona 500 and became the de facto drag racing standard. The 426 and modern Hemis have dual rocker shafts, similarly sized valves, and two similarly-placed valves per cylinder. The Hemi was 56 pounds lighter than the 5.9 truck engine when it debuted.

John Veatch added: “The engine came in at 345 cubic inches of displacement and 345 hp, the same as the 1957 DeSoto Adventurer 345 Hemi, the first standard engine to make the one horsepower per cubic inch mark (the 1956 300 optional high performance engine had also done so). Both preceded the optional 1957 Corvette engine [generally credited with one horsepower per cubic inch].”

Guidance for Mopar Hemi engine owners

If you have an MDS engine (all current 5.7 engines!), only use 5W20 oil. You need the right oil. If the owner’s manual says something else, follow its advice, but don’t be convinced by anyone else. Insist on the right grade and if they don’t use it...get a refund and go somewhere else. (See TSB 09-015-04 and 09-013-04: “Vehicles with the Multiple Displacement System must use SAE 5W-20 oil. Failure to do so may result in improper operation of the MDS.”) Engine problems have been reported as being due to the use of the wrong oil. Usually, these problems can be resolved with an oil change, but not always.

Other Hemi V8 engine notes

new Dodge Hemi engineThe Hemi V8 has pushrod-operated overhead valves, sequential multiple-port returnless fuel injection, and a compression ratio of 9.6:1. Valve gear is within the head walls. Mike V. wrote:

... to supercharge a Hemi correctly, you should swap out the pistons. ... The Edelbrock eForce is an amazing kit. It is a bit chunky looking, but it will fit right. The advantage of the Edelbrock over other similar Eaton-based kits is the fact that it uses a separate belt, pulley, and tensioner system, for greater reliability.

As for MultiAir, Bob Sheaves wrote, “Adding MultiAir would take a complete set of engine castings, requiring complete cooling system changes and a whole raft of other stuff. It would take at least three years from the start of program approval.”

2004 Hemi specifications (courtesy Cole Quinnell)

Bore x Stroke3.92 x 3.58 in, 99.5 x 90.9 mm
Valve Systempushrod, 16-valve, hydraulic roller lifters
Block Constructioncast iron, deep skirt, cross-bolted main caps
Centerline of crank to head deck face9.3 inches
Centerline of crank to centerline of cam7.4 inches
Centerline of crank to oil pan rail2.6 inches
Block maximum deck width at deck face18.3 inches
Block height, oil pan rail to top of water outlet15.4 inches
Overall engine length21.1 inches
Combustion chamber volume84.9 cc
Intake valve angle18°
Intake valve head diameter50.8mm, 2.00 inches
Exhaust valve angle16.5°
Exhaust valve head diameter39.4mm, 1.55 inches
Oil Capacity7 quarts (6.6 liters)
Weight (with induction, wiring, flexplate,
and exhaust manifolds, but not accessories)
485 lbs
Modern Hemis 5.7 Hemi • SRT 6.1 and 6.46.4 Truck Hemi • Supercharged “Hellcat”
Classic Hemis 426 HemiOld Hemi History • 392 Crate HemiDevelopmentPlane Hemi
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