In the 1950s and 1960s, if you mentioned to someone that your car had a Hemi engine you immediately gained respect. The Hemi was known as a powerhouse, and in automotive circles, it was tough to beat. Sadly, the cost to build the Hemi and strangling insurance regulations led to the demise of the legend in 1972.
With the introduction of the 2003 model year, the legendary engine made a return. However, production of the engine actually began in June 2002 at the Saltillo plant in Mexico. In 2003, Chrysler showed a Hemi engine with a supercharger to the public. Using the 5.7 Hemi engine and a Whipple supercharger, that engine made 430 hp and 480 ft-lbs of torque. That doesn’t sound like a lot, but for a completely new engine design, it was a start. The engine initially found its way into Dodge trucks.
For this, its third, generation of design, Chrysler incorporated some new build processes and design features. The block, for instance, is precision cast and the connecting rods are powder metal.
The Gen III Hemi was designed with two spark plugs per cylinder. One coil pack was over each spark plug, and a plug wire also connected from that coil pack to a spark plug on another cylinder (each cylinder shares a coil pack with another cylinder). This means that a separate coil fires each of the two plugs on a given cylinder. One spark plug fires during the power stroke to begin the combustion process and the second spark plug fires during the down stroke of the piston to help burn any residual fuel and hydrocarbons that didn’t burn during combustion.
The 5.7-liter Hemi V-8 found in the new 2006 Charger Daytona featured 350 hp and 390 ft-lbs of torque. That’s 10 horses over the previous year’s 5.7-liter Hemi that came in the R/T Charger. Engineers at Chrysler say that the horsepower increase was accomplished by using a less restrictive intake system, and by moving to a straight-through muffler design instead of the previous years’ three-pass muffler. A styling enhancement meant that the Daytona also received a color-matched engine cover. (Photo Courtesy Fiat Chrysler Automobiles US LLC)
Over the years, the third-generation Hemi has undergone many revisions, and when looking for an engine, some of these revisions can affect choices in aftermarket parts. Do you have an idea of how you want to build your Hemi? Are you looking for a max-performance monster, or do you want to just add some bolt-on parts to increase the performance? Either way, you need to know which late-model Hemi you actually have.
The 5.7-liter Hemi engine made its 2003 debut in the Dodge Ram as the standard engine. That first generation was capable of producing 330 hp at 4,800 rpm, and 375 ft-lbs of torque at 4,200 rpm. The 5.7-liter Hemi engine was also available in the Dodge Durango.
By the time the 2005 model year cars were introduced, the 5.7-liter Hemi had become a proven performer, so it was a natural fit to make its way under the hood of the new LX-platform cars, including the 300 and the Magnum (eventually the Charger, in 2006). The Hemi was smaller and cheaper to build than the older LA-series small-block that it replaced, but produced more power and torque.
When building the engine, designers incorporated a very strong deep-skirt design into the block. The deep-skirted block made it possible to create a stronger, four-bolt support system for the crankshaft. This means that supporting the crankshaft are four bolts at each main bearing (two that mount vertically through the bearing cap, and two that mount horizontally through the block into the bearing cap). The new Hemi block is precision cast, and this allows it to be much lighter than other engines of the same relative size.
The pistons are made using a cast eutectic alloy, and are relatively light (413 grams). It’s believed that using a relatively small cylinder bore and a long stroke can aid in reducing emissions, so the cylinder bores of the 5.7-liter Hemi were designed at 3.197 inches, and the crankshaft stroke comes in at 3.578 inches.
The connecting rod was also designed to minimize weight but keep some much-needed strength. The connecting rod is built using a powder metallurgy. This is the process of blending fine-powdered materials, and then compressing them into a desired shape or form. Once this “compacting” is complete, the connecting rod is then heated in a controlled atmosphere (called sintering) to bond the material/powder into the desired product.
The 5.7 Hemi used in cars from 2003 through 2008 used short blocks that interchange between car and truck engines. The difference is that all cars since 2005 are MDS equipped with the solenoids and lifters. In 2007 the Ram and Durango also benefited from the addition of MDS. With the exception of a few minor sensor changes these short blocks are identical. (Photo Courtesy Fiat Chrysler Automobiles US LLC)
The 2003–2008 5.7-liter Ram with a 5.7-liter DR (truck) engine used a seven-rib front accessory drive; the front cover, water pump, and accessories do not interchange. This setup mounts the accessories high in front of the intake, prohibiting the use of car intake manifolds. (Photo Courtesy Fiat Chrysler Automobiles US LLC)
The cylinder block of the new Hemi is precision cast. This process of making the block allows it to be lighter than other 5.7-liter engines. This is accomplished even though it has a taller deck height than GM’s equivalent V-8.
The use of powder-metal technology eliminates the need to manufacture the product by traditional forging and metal removal processes (casting and machining), thereby reducing costs. Also, instead of using a through-bolt with a nut, as with previous engine designs, Chrysler employed a cap bolt. The result is a 6.24-inch connecting rod that is more than sufficient in stock applications.
All 2008 and earlier 5.7- and all 6.1-liter engines have a 32-tooth reluctor wheel. All 2009 and later 5.7-liter engines have a 58-tooth reluctor wheel.
The crankshaft has large inner counterweights but doesn’t result in an unnecessarily heavy crankshaft. The crankshaft features radius leading-edge counterweights and is definitely performance oriented. The factory 5.7- and 6.1-liter Hemi V-8 crankshafts do interchange, but the reluctor wheel on the 5.7-liter uses three mounting bolts whereas the 6.1-liter uses four bolts.
The new Hemi also features a camshaft that is located considerably higher within the block than on previous V-8 designs to minimize the pushrod length required to operate the rocker arms. Shorter rocker arms deflect less, creating a more stable valvetrain. To help keep the weight down, the cam is a hollow-core billet piece. The stock 5.7-liter Hemi camshaft measures .477/.462–inch lift, and 255/236–degrees duration. As built, the stock valvetrain is good to around 6,200 rpm.
The Gen III Hemi uses a block with Siamese bores. Siamese cylinder bores are generally more stable than cylinder bores that are cast as part of the engine block. Siamese bores are often used with aluminum blocks because the steel cylinder inserts of the Siamese bores add rigidity.
The stock rocker arms in your Hemi engine are a cast design. Although they perform well in your production engine and are interchangeable from 5.7 and 6.1, they can be considered a weak link when valvespring pressures are increased.