When Francois Castaing found himself Chrysler’s head of engineering, he found engines that had fallen behind in performance and were barely making emissions rules. Rather than patch up old designs—the V8 was loosely based on a 1951 design—e ordered brand new engines, for the most part. That brought the “Neon” 2.0 and 2.4; the 3.5 V6; and a new V6 and V8, the 3.7 and 4.7. Now they only needed a replacement for the 360 (5.9) V8 in Dodge trucks.
They could have made a bigger version of the 4.7, but Bob Lees, leader of the 4.7 V8 project, thought they could do better. He looked to hemispherical heads, used in Chrysler’s first V8s, for the answer.
The 4.7 liter V8 High Output peaked at 270 horsepower and 330 pound-feet of torque—easily ahead of the outgoing 5.2 (220 hp, 300 lb-ft) and not bad when compared with the old 5.9. More was needed for the future, though; and the new V8, coded Eagle, delivered it, with 345 horsepower at 5,600 rpm and 375 lb-ft of torque (4,400 rpm) — one net horsepower per cubic inch, and well out of the old 360’s league when the “New Hemi” debuted in the 2004 Ram. That wasn’t the limit; hot versions of the Hemi V8 came out quickly, the 6.1 at 425 horsepower (matching the gross output of the 426), a 6.4 at 485 horsepower, and finally a 2023 6.2 Supercharged hitting 1,025 horsepower.
The original Eagle Hemi came in several versions, differing partly in their air path; the Dodge Charger had slightly less horsepower than the Ram 1500, but 15 lb-ft more torque. The Hemi V8 in the Chrysler 300C, Dodge Magnum, Dodge Challenger, and Dodge Charger had a “multiple displacement system” (MDS) which shut off fuel to four cylinders when less power was called for. The system later made its way to pickups as well.
| 5.7 | 2004 Ram | 2005 Charger |
|---|---|---|
| EPA mpg | 14/18 | 15/23 |
| Horsepower | 345 @ 5,600 | 340 @ 5,000 |
| Torque | 375 @ 4,400 | 390 @ 4,000 |
Despite its hemispherical-head design and far greater power, the new Hemi V8 was cheaper to build than the old LA series 360 V8 it replaced; it was reputedly even cheaper than the “Next Generation” 4.7 V8 designed by the same team. It was also 56 pounds lighter than the 5.9. The original Hemi had been far too expensive and hard to build, but decades of automation in the factories and advances in materials and valvegear design made it all possible.
| 5.7 | 2004 Ram Hemi | 2003 Ram 360 |
|---|---|---|
| EPA mpg | 14/18 | 12/18 |
| Horsepower | 345 | 245 |
| Torque | 375 | 335 |
The 2004 Hemi: gains of 2 mpg city, 100 horsepower, and 40 lb-ft of torque—and lighter and cheaper.
The meaty deep-skirt cast iron block was meant for durability in truck use; the crankshaft was supported by two horizontal and two vertical bolts at each main bearing. The iron block was mated to aluminum heads and a plastic intake manifold, which was light but had extremely good airflow. The factors that made the Hemi durable in trucks made it doubly durable in cars.
Both the Eagle 5.7 and the famed 426 Hemi, created for racing and only joined by a “street” version years later, had dual rocker shafts. They also had similarly sized valves, two per cylinder, in similar locations.
John Veatch observed that its displacement was carefully chosen—345 cubic inches, the same as the first standard engine to reach one horsepower per cubic inch, in the 1957 DeSoto Adventurer. (The later 1957 Corvette engine is often credited with this; but that engine was optional, as was that of the 1956 Chrysler 300 which also reached one horsepower per cubic inch.)
At least two veteran engineers were consulted; Tom Hoover, “Father of the 426 Hemi,” told Hot Rod that he suggested raising the camshaft to shorten the pushrods (reducing valve-train inertia and simplifying the rocker arms) and adding squish area for light-load efficiency and lower emissions. Willem Weertman, head of engine design in the 1960s and 1970s, suggested using dual spark plugs for each cylinder to fix emissions problems. Sequential multiple-port returnless fuel injection also helped with emissions and power.
Some scoffed at the pushrod-operated overhead valves. Any scoffing did not last long.
Production began in June 2002 at the Saltillo plant in Mexico—the home of every modern V8. It was unveiled in Ram trucks in December 2002. The first supercharged engine was shown to the public in January 2003, in the Magnum SRT-8 and 300C concepts; but buyers would have to wait many years to actually buy a supercharged Hemi.
In 2005, Hemi engines were specified by around 45% of buyers on cars and trucks where it was optional. Retired tuning chief Pete Hagenbuch joked at the time that it was the most successful Hemi ever, because it could be built at a profit.
Still, the new Hemi was one of the few new engines of its era lacking variable valve timing. The team knew that it could improve efficiency in other ways, too. The next few years were spent fixing flaws and creating a new version with greater power and efficiency.
The dual spark plug design (credited to both Willem Weertman and Tom Hoover) let a Hemi engine pass emissions rules; the second plug fired during the power stroke to help burn the fuel more thoroughly. To a small degree, it also provided extra power in the downstroke; and it allowed the initial firing to take place closer to top dead center. Its main goal and purpose was to cut oxides of nitrogen and ozone.
Each cylinder had a coil pack over one spark plug, while the other had a wire running to a coil pack on the other side of the engine. Each coil pack fired both its own plug and a plug on the other bank of cylinders. That allowed for the dual-sparks system and strong primary sparks without doubling the number of coils to 16.
In 2009, Chrysler claimed the cylinder deactivation (MDS) had saved around 100 million gallons of gasoline between 2005 and 2009, cutting carbon dioxide (CO₂) emissions by close to a million metric tons.
After the Cadillac “four-six-eight,” the 2005 Chrysler 300C and Dodge Magnum R/T were the first modern, high-volume cars in North America to use cylinder deactivation. It was part of the design goal from the very start. Bob Lee, Powertrain Product Team vice president, said this made it “elegantly simple and completely integrated into the engine design. The benefits are fewer parts, maximum reliability and lower cost.”
The system moved from eight to four cylinders in 0.04 seconds by closing the valves in half the cylinders. Some energy was lost through compression, but none by pumping air through the unused cylinders; so fuel economy rose by around 10% overall. Lubrication was handled by sending oil through the pushrods.
The system was ideal for V8s because of the engine’s balance on four cylinders; V6 makers would handle that, years later, by shutting just two cylinders. Today, even Mazda four-cylinders have a similar system, moving to two cylinders at times.
The Hemi always shut off the same cylinders; they tested the engines over many miles and found no serious wear patterns. The system did prove to be reliable but very sensitive to oil grades, and many early engine failures were traced down to mechanics using the wrong grade of oil.
It didn’t take long for an all-out-performance version, the 6.1 Hemi, to arrive for the Dodge Magnum SRT-8, Chrysler 300C SRT-8, and the Dodge Charger SRT-8 and Challenger SRT-8. With that move, and especially once a 6.4 liter version with better fuel economy arrived, the 5.7 became more of an economy V8—though its power did not decline at all—and a mainstay for pickup trucks. In the Ram 1500 pickup, the 5.7 Hemi remained the top primary power engine—except for the Viper-powered Ram 1500 SRT and the later supercharged Ram TRX—until the 2025 models brought new twin-turbo Hurricane six-cylinders into play. Thus is became a truck workhorse while still providing quite good power for cars.
The second generation “Eagle” 5.7 Hemi had a clever hydraulic cam phasing system, which was inexpensive but expensive; by moving the cam slightly, valve timing and lift was optimized for idle, low power, or high power. The camshaft (as before, a hydraulic roller setup) had oil passages to drive the cam phaser sprocket.
| 5.7 | 2002 Ram | 2009 Ram |
|---|---|---|
| Horsepower | 345 | 390 |
| Torque | 375 | 407 |
| EPA mpg | 14/18 | 13/19 |
The engineers also increased the compression ratio and improved airflow in the intake, heads, and exhaust. They added an active intake manifold, borrowed from the 3.5 liter V6 but in some ways based on Chrysler’s research in the 1960s. A flapper door switched air bewteen long runners and short runners, allowing either better torque at low engine speeds or higher horsepower at higher engine speeds.
| 5.7 | 2006 Charger | 2009 Challenger | 2011 Challenger |
|---|---|---|---|
| Horsepower | 340 @ 5,000 | 375 @ 5,800 | 379 |
| Torque | 390 @ 4,000 | 398 @ 4,200 | 410 |
| EPA mpg | 15/23 | 16/25 | 17/25 |
There were other changes, including new piston/rod assemblies with thinner walls and a stronger-alloy pins. Ports were redesigned, intake valves made 2mm larger, and the exahust floor was raised. Finally, the engineers specified a stronger crankshaft, dual-mass crankshaft damper, floating pin pistons, new valve springs, and higher capacity oil pump; some believe the new pump still didn’t have the capacity it needed.
| 5.7 | 2002 Ram | 2009 Ram |
|---|---|---|
| Horsepower | 345 | 390 |
| Torque | 375 | 407 |
| EPA mpg | 13/17 | 13/19 |
The horsepower rating of the little 5.7 was not nearly identical to the net power rating of the famed 426 Hemi; torque was not quite at 426 levels, but at over 400 lb-ft, it was still quite impressive. The effort involved in creating the 5.7 Hemi had turned out to be very well spent; the Hemi engine itself sold many cars and trucks, and the 4.7 V8 itself was dropped even after a “Hemi-style” head and valvetrain redesign gave it more power. There was just no point, with the Eagle providing similar gas mileage and much higher performance at the same (some said lower!) cost.
The correct grade of oil was essential; the owner’s manual is the only correct source, but the MDS engines have always used 5W20 oil. Two service bulletins, TSB 09-015-04 and 09-013-04, made that clear: “Vehicles with the Multiple Displacement System must use SAE 5W-20 oil.”
Some owners had problems with rapid cam wear. “AHBguru” talked to police fleet mechanics (keeping in mind that police use is quite harsh on engines) and found that the final update to valve lifters was made in early 2019, with trucks getting the new parts in January and other engines upgraded by March. They superceded all prior lifters, across the board, from 2005 to 2019 (save for the old pre-MDS truck engines).
The latest and greatest lifter update occurred in early 2019. New trucks started getting the lifters that January, everything else by that March; the new parts replaced all prior lifters in MDS (cylinder deactivation) 5.7 Hemi V8s from 2005 to 2019, and were available for ordering at dealerships. These apparently resolve issues with cam and lifter failure, though not from use of the wrong oil and so on. Replacing lifters and cams costs under $2,000, taking around ten hours. Chrysler also added a new standard procedure of dropping the oil pan for inspection since cam or lifter failure often also hurt the oil pump and pickup.
“Hemi tick” can, according to Allpar’s Mentallica, be a lifter tick; a failing MDS lifter; a broken exhaust manifold bolt; a cracked manifold or head; or a bad seal on the exhaust manifold—or any number of other things. On top of that, the engine normally does make a relatively quiet tick on startup, quieting down fairly quickly. A loud tick should be addressed. Some believe the issue came in with MDS, but that doesn’t appear to be true. Geoff Gariepy clarified the normal tick—“very briefly sounds like a diesel engine’s clatter on startup. After a second or two, that's gone, and it’s replaced by a very mild ticking sound reminiscent of a valve train noise.”
AHBguru added that broken exhaust bolts are uncommon on cars and Jeeps, and more common on Rams. Cracked intakes are unusual, as are cracked heads; but bad head gaskets, dropped valve seats, and broken valve springs are more common. He also noted that Chrysler seems to be recommending engine replacement when the VVT solenoid is plugged with debris from a cam or lifter failure.
The cam was hollow to reduce weight; it had oversized journals and lobes to reduce lifter side loading. The company used the beehive valve springs it had invented, which could be made lighter but still have less lifter collapse. The light rockers had just .500 inches of lift in the early engines, but the high airflow of the Hemi design made this acceptable.
Precision casting cut weight off the block despite its high deck height; the skirt was coated to reduce noise and make the range of ring seal sizes larger. The cast eutectic alloy slipper-style pistons weighed just 413g; they were anodized on the top ring to provide a heat barrier and anti-micro-weld mix. That also let the engineers move the top ring to just 3 mm from the top of the piston. Thin rings presumably reduced friction, while a groove under the top ring cut pressure between the top two rings.
A windage tray was standard to prevent oil shortages. The serpentine belt pulley doubled as a vibration damper. No balance pad was needed as the connecting rods were strong and light.
The ports had peak flow at 0.375 inches. Popular Hot Rodding compared intake and exhaust ports favorably to the GM LS6 V8 engine.
Chrysler used its usual a speed density system instead of a mass airflow sensor.
Courtesy Cole Quinnell and Allpar
| Bore x Stroke | 3.92x3.58” 99.5x90.9 mm |
| Max deck width at deck face | 18.3 inches 464.8 mm |
| Block height | 15.4 inches |
| Engine length | 21.1 inches |
| Combustion chamber vol | 84.9 cc 5.18 cid |
| Intake valve angle | 18° |
| Intake valve diameter. | 50.8mm 2.00 inches |
| Exhaust valve angle | 16.5° |
| Exhaust valve diameter |
39.4mm 1.55 inches |
| Oil Capacity | 7 quarts 6.6 liters |
| Weight* | 485 lbs |
* Weight includes manifolds, wiring, flexplate, and exhaust manifolds, but not accessories such as alternator
Crank centerline to...
| head deck face | 9.3” |
| cam center | 7.4” |
| oil pan rail | 2.6” |
Books by MoTales writer David Zatz
Copyright © 2021-2024 Zatz LLC • Chrysler / Mopar car stories and history.
