From SRT to Demon, Here’s Everything There Is to Know about the 2003 to 2023 Gen III Hemi V-8 – Daniel Strohl @Hemmings

From SRT to Demon, Here’s Everything There Is to Know about the 2003 to 2023 Gen III Hemi V-8 – Daniel Strohl @Hemmings


For 20 years, a veritable pandemonium of Hemis powered everything from modern muscle cars to trucks and SUVs

While many cars and trucks of the Eighties and Nineties dispelled the notion that American performance died off with the original muscle cars, it took an entirely new engine—one more powerful and less expensive to produce than its predecessor—to reignite the horsepower wars and usher in a new golden age. The Hemi V-8 has since become a standard-bearer for Chrysler, Dodge, Ram, and Jeep vehicles, and its basic engine architecture has spawned more than a dozen configurations, some of them difficult to discern from others. For that reason, we’ve put together this spotters guide to the third-generation (or gen 3) Hemi family of engines

What Sets the Hemi Apart

Teased in the 2000 Chrysler 300 Hemi C and the 2001 Dodge Super8 Hemi, the new 5.7-liter Hemi (Chrysler stylizes it as HEMI, but for expediency’s sake, we will not) debuted in the 2003 Dodge Ram pickups, featuring a deep-skirt cross-bolted iron block, aluminum heads, overhead valves, 4.46-inch bore spacing, the same bellhousing bolt pattern as the Chrysler LA-series V-8s, coil-on-plug ignition, composite intake manifolds, multipoint fuel injection, and that controversial head design.

Like the second-generation 426 Hemi, the 5.7L Hemi heads featured a camshaft in the block, opposed valves for a true crossflow design, twin spark plugs, and rocker shafts. The third-generation Hemi did not, however, feature a full hemispherical combustion chamber. Instead, Chrysler’s engineers decided to flatten either side of the combustion chamber to improve combustion efficiency and emissions. Some might argue that doesn’t make the engines true Hemis, but then again, the Hemi V-8s of yore were massive, heavy engines that cost a lot to machine and that wouldn’t meet modern-day fuel-efficiency or emissions requirements

Even though prevailing internal combustion engine design called for multiple valves operated by overhead camshafts (indeed, one of the engines the Hemi replaced, the 4.7L PowerTech V-8, used single overhead camshafts), the Hemi stuck with a two-valve, pushrod design. As they did with GM’s LS-series V-8s, critics scorned that layout as antiquated and unable to meet power, mileage, and emissions demands. However, Chrysler’s engineers made the most of it by taking Tom Hoover’s advice to relocate the camshaft upward in the block, thus shortening the pushrod length and improving valve train geometry.

What’s more, as Allpar reported, the Hemi proved less expensive to manufacture than previous hemispherical-head designs, which meant the engines could turn a profit just as easily as they could turn into ad copy gold.

5.7-Liter Hemis

After debuting in the Ram truck line, by 2005 the Hemi migrated to the LX-chassis cars (Dodge Charger R/TDodge Magnum R/TChrysler 300C) with the same 5.7-liter ( displacement but a few changes. Truck engines—rated at 345 horsepower in the Ram, 335 horsepower in the Grand Cherokee, Durango, and Aspen—continued to use their own intake manifolds that mounted the throttle body atop the manifold. Meanwhile, car engines—rated at 350 hp in the Charger Daytona R/T and 340 hp in the other cars—moved the throttle body to the front of the intake. The 2005 car engine revisions also saw the introduction of the Multi-Displacement System, which deactivates four of the eight cylinders at cruising speed to improve mileage.

The most significant revisions to the entry-level Hemi came in 2009, with the so-called Eagle 5.7L Hemi. The 3.917-inch bore and 3.58-inch stroke remained the same, but Chrysler engineers added new heads, which reduced the combustion chamber volume from 85-cc to 65-cc and which flowed better with square intake ports and D-shape exhaust ports; Variable Camshaft Timing, which advances or retards timing by up to 37 degrees; larger intake valves; beefier connecting rods; a 58-tooth crankshaft sensor wheel; and a 10.5:1 compression ratio. The Eagle Hemi also features an active intake manifold with a flapper door that switches from long intake runners to short runners at higher rpms. The end result: anywhere from 360 to 375 horsepower in cars and SUVs and anywhere from 383 to 395 horsepower in Ram trucks.

Note that Chrysler engineers also built a version of the Eagle 5.7L specifically for the 2009 Durango and Aspen hybrids. These used a special camshaft and still used EGR valves after Chrysler had eliminated EGR from all other Hemis. Poorly received when new, the likelihood of coming across one of these in the wild nowadays is slim.

To identify one, look for a “5.7L” cast into the side of the block just above the oil pan mounting surface.

SRT Hemis

Along with the 2005 changes to the 5.7L, DaimlerChrysler also introduced the first SRT-8 engine that year, the 6.1-liter ( Hemi. More than just a bump in displacement thanks to a larger 4.055-inch bore, the 6.1L featured an aluminum intake manifold (the only third-gen Hemi that didn’t have a composite intake manifold), forged crankshaft, D-port cylinder heads with 74-cc combustion chambers and 2.08-inch intake valves and 1.60-inch sodium-filled exhaust valves, aluminum exhaust manifolds, bigger fuel injectors, oil squirters aimed at the underside of the pistons, and a more aggressive camshaft. Combined, these modifications make for a nice heritage-inspired horsepower figure of 425 (in the SRT-8 versions of the 300C, Magnum, Charger, and Challenger; 420 in the Grand Cherokee SRT-8). Look for a “6.1L” cast into the side of the block just above the oil pan mounting surface.

Rather than upgrade the 6.1L as with the Eagle 5.7L, in 2011 Chrysler engineers replaced the 6.1L altogether with the 6.4-liter Hemi, also sometimes referred to as the 392 or the Apache, an engine that technically debuted in 2010 on the Challenger Drag Pack cars. Along with the displacement increase (the result of a larger 4.090-inch bore and a longer 3.72-inch stroke), the 6.4L benefited from a 10.9:1 compression ratio, 2.14-inch intake and 1.65-inch exhaust valves, the 6.1L’s oil squirters, an even more aggressive camshaft, and an active intake manifold like that found in the Eagle 5.7L. Initially rated at 470 horsepower, the 6.4L bumped to 485 horsepower in 2015 with the introduction of the Scat Pack cars (Grand Cherokee and Durango SRT versions of the 6.4L bumped too, but just to 475 horsepower; the 6.4L in the Wrangler Rubicon 392 produces 470 horsepower). All 6.4L car and SUV engine intake manifolds have a front-mounted throttle body angled toward the driver’s side of the vehicle. Look for a “6.4L” cast in the side of the block.

At roughly the same time that FCA bumped the output of the 6.4L, it also made the larger Hemi available in the Ram 2500 and heavier trucks. Essentially similar to the 6.4L used in the cars and SUVs, the truck version used a BGE (Big Gas Engine) block with improved casting processes, higher nickel content, and a slightly more rigid design. Horsepower figures varied from 366 to 410, depending on the application. Look for a “BGE” cast into the side or back of the block and an intake manifold that angles the throttle body toward the passenger’s side of the vehicle.

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