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CHAPTER 1

THE GEN III HEMI

The Hemi story begins with a military aircraft project in 1944–1945 called the Xi2220. This V-16 engine was designed and developed by Chrysler engineers and produced more than 2,500 hp in 1945. That’s just above 1.1 hp/ci. A few years after the end of World War II, Chrysler engineers were asked to design a new production engine, and they selected the Hemi head.

Chrysler introduced the new 331 Hemi production engine in 1951. DeSoto and Dodge soon followed with their own smaller versions of the Hemi. After the 331’s introduction, Chrysler launched larger versions of the new engine with the release of the 354 and the 392. The 392 was the first engine that could be raced on alcohol and nitromethane fuels with a supercharger and survive. The production of the 392-Hemi family ceased in 1958. These three Hemi engines (the 331, 354, and 392) made up the Gen I branch in the family tree. However, it did not receive this nickname until the early 2000s.

The next member of the Hemi family was introduced in 1964 as the soon-to-be famous 426 Hemi. Tom Hoover and his design and engineering team created the 426 based on Chrysler’s big-block wedge engine called the B engine or, more specifically, the RB engine. This big-block had been in production since 1958 and replaced the 392. The 426 Hemi was rated at 425 hp, and it was produced through 1971.

The 426 Gen II Hemi has a tall block, thick valve cover, and tall height to the top of the air cleaner, which results in a wide overall assembly. This is true of all the 1964–1971 Hemis, including race, street, and the few 4-barrels. (Photo Courtesy FCA US LLC)

In eight years of production, Chrysler built 10,669 of the Gen II 426 Hemi engines. The Chrysler 426 engine was brought back by Mopar Performance in 1995/1996, first as parts and then as a crate engine copy of the original 426.

The next generation of Hemi engines was introduced in 2003. The 5.7L engine was the first of the Gen III Hemis. It was followed by three more displacements: the 6.1L, the 6.4L, and the 6.2L. Today, three of the four are still in production, as the 6.1L production ended in 2010.

All of the Gen III Hemi engines are V-8 and feature twin-plug heads, a feature first developed for the Gen II 426 Hemi in the early 1970s. These production engines feature cast-iron blocks and aluminum heads with wide plastic valve covers (black), a beer-barrel shaped intake manifold, multi-point injection (MPI), and a serpentine-belt front accessory drive. In the 14 years of production of the Gen III Hemi engines, there have been approximately 3.8 million engines/vehicles produced. From 2011 to 2017, nearly 130,000 6.4L 392 engines have been built, which is 9.1 percent of production per year or about 30,000 per year at current levels. Currently, the Hellcat and Demon are limited-production options that are restricted to a few thousand per year.

Most of the Gen III Hemi engine assemblies tend to look alike, similar to this Mopar Performance complete 426 crate motor assembly. The direct-mount individual coils bolt to the valve cover and hide the dual-plug feature. The large 4-barrel throttle body on top of the manifold is somewhat unique. It is hard to tell that it has an aluminum block. A stock 6.1L Hemi is shown at the beginning of chapter 2.

Hemi Engine Names

Typical of most large engine projects, the newer Gen III engines were given official code names that became the common nicknames for a particular hardware package. The first three are named after airplanes: the 5.7L Eagle, the 6.4L Apache, and the 6.2L Hellcat. The fourth is the Demon. The 5.7L Eagle is rated at 375/390 hp (up from the original 345 hp) and was introduced in 2009. The 6.4L 392 Apache is rated at 485 hp and was introduced in 2011. The 6.2L Hellcat is rated at 707 hp and was introduced in 2014 as Chrysler’s first supercharged engine. The Demon was introduced in 2017 and is rated at 840 hp.

Of the four production displacements that have been used in the 14 years of Gen III Hemi production, the most popular or most common based on volume is the 5.7L. It has been produced the entire production run, and it has been installed in cars, trucks, and SUVs. The next most popular based on volume is the 6.4L 392. It is one of the newer versions and has just recently been added to the truck line (called the Big Gas) and to the SUV line (as an SRT8 model).

Additionally three nonproduction (racing) displacements are offered: the 354, 362, and 426. The 354 is a supercharged Gen III Hemi used only in the Challenger Drag Pak for drag racing. While similar to the production Hellcat, it has features unique for racing. The 362 is a circle track (Canadian series) engine and is available in crate engine form from Prefix. The Gen III 426 is an aluminum-block version that is used in the Challenger Drag Pak naturally aspirated models (also available from Prefix).

Production Engines

By the 2017 model year, more than 3.8 million Gen III Hemis had been produced. That’s a lot of engine assemblies! Compare this huge number to approximately 10,000 426 Gen II Hemis that were built during eight years of production and about 120,000 units of the 6.4L 392 that Chrysler has built during its seven years of production.

While the newer engines have project nicknames such as Eagle and Apache, only the Hellcat and Demon (shown) have on-car logos.

The original Gen I 392 was introduced in 1957–1958 at 325 to 345 hp with the high-performance version (the 300D) around 1 hp/ci and 380 hp. The 5.7L 345-ci Hemi of 2003 rated at 345 hp, and the Eagle package, introduced in 2009, increased horsepower to around 366 to 390 hp. The newer and larger 6.1L version was rated at 425 hp, which matches the original Street Hemi Gen II power rating in 1966–1971 models with 54 fewer cubic inches: 372 versus 426. Keep in mind that the Society of Automobile Engineers’ (SAE) engine/horsepower rating system made it much more difficult to generate 425 hp in 2010 than the rating system in the 1960s.

In 2011, the even larger 6.4L 392 Hemi was rated at 470 hp! All of this was topped in 2014–2015 with the introduction of the 6.2L Hellcat supercharged engine, which was rated at 707 hp. It was Chrysler’s first supercharged engine and the highest horsepower rating of any production engine through 2016. The 2017 Demon moved the goalpost again with an overwhelming 840 hp!

The 5.7L Engine

The 5.7L 345-ci engine was just slightly larger than the 1968–1973 340 A-engine performance small-block. It used a 3.917-inch bore, which was sometimes rounded up to 3.92 inches. The 5.7L has a stroke of 3.58 inches, similar to the 360 and 5.9L small-blocks that are bigger versions of the 340. The original power rating for the 5.7L was 345 hp in 2003. This rating yields a 1 hp/ci factor, which is excellent for any V-8 production engine, especially bigger V-8s. The original Gen II Hemi was 1 hp under at 425 hp from 426 ci.

The original 5.7L engine was produced from 2003 to 2008, and the 5.7L Eagle was introduced in 2009 and still produced today. The high-performance Eagle package was based on a new high-flow cylinder head with larger ports and bigger valves. The Eagle intake valves were 2.05 inches compared to the standard 2 inches. The valves were also about 0.300-inch longer and the installed height was increased to 1.99 inches, up from 1.81 inches. The bigger ports and bigger intake valves allowed the Eagle intake ports to flow about 40 cfm more than the standard 5.7L. The Eagle version also makes about 30 to 45 hp more (366 to 390) than the original.

Engine Specifications

Each engine discussed is defined by a specific group of specifications. In addition, Chrysler built these engines in specific model years. In general, the 5.7L and the 6.1L are the oldest and most likely to be rebuilt at this time. The Demon Hemi uses a bigger supercharger than the Hellcat and uses more boost pressure to gain the extra horsepower. Its basic specs are the same as 6.2L Hellcat.

Racing Specs

The three nonproduction engines (354, 362, and 426) were originally built as racing engines. However, they were designed as crate engines that could be retuned for street or dual purpose usage by the manufacturers. These nonproduction engines were offered through the Mopar Performance program and its related Drag Pak program. Today, Prefix and many engine builders offer them. The original 354 Drag Pak engine used a cast-iron block, but the aluminum block used in the 362 and the 426 is now optional at the original bore size. ■

This cutaway of the 392 Gen III Hemi shows the internals of the production engine, also called a 6.4L. Except for the intake system, it is similar to the 6.2L Hellcat/Demon supercharged engines. (Photo Courtesy FCA US LLC)

Because of these changes, swapping parts from the new 5.7L Eagle to the original 5.7L does not work. Rebuilds must use basic service parts for the engine being rebuilt. There are some exceptions, which I’ll discuss in future chapters.

The 6.1L Engine

The 6.1L 372-ci Hemi engine was introduced in 2006 and was produced through 2011. It was a big-bore version of the 5.7L with a 4.055-inch bore that was sometimes rounded up to 4.06 inches. This bigger engine had a different block casting but shared the 3.58-inch stroke with the 5.7L. It was originally rated at 425 hp or 1.14 hp/ci.

The 6.1L’s 2.075-inch valves were slightly larger than the 2.05-inch valves of the 5.7L Eagle, but they were much larger than the original 5.7L’s 2.00-inch valves. The valves are slightly longer and the installed spring height is slightly higher (1.87 inches versus 1.81 inches).

The key to this engine’s performance package is the much bigger camshaft. The 6.1L’s valve lift increased almost 0.100 inch more than the 5.7L standard and Eagle cams, going from 0.472-inch to 0.571 inch lift and 0.460 inch versus 0.551 inch on the exhaust. The advertised duration picked up about 20 degrees, showing 260 versus 283. At 0.571-inch valve lift, this has to be one of the highest lift cams ever used in a production engine. The previous high-lift, high-performance production engine cams of the muscle era (426 Hemi, the 340, the 440-6, etc.) used cams with production lifts around 0.450 to 0.475 inch. High-performance aftermarket cams for these engines tended to peak at around 0.510 inch. The 0.571-inch lift was impressive for production, street, warranty, and emissions considerations! The 6.1L engine was the only V-8 engine in the SRT models in this era.

The 6.4L 392 Engine

The 6.4L 392-ci version of the Gen III Hemi engine had somewhat of an identity crisis. It was originally called the 392, then production called it the 6.4L, and then it was back to the 392. It is the same displacement either way. In the last couple of years, production seems to have settled on 392.

This 392 engine package is also called the Apache. It is rated at 470 hp (2011) or 490 hp (2016–2017), which is 1.20 hp/ci. It has the largest valves to date from the production Gen III Hemi engines with 2.138-inch intakes and 1.654-inch exhausts. It also features the raised valvetrain with the tallest installed spring heights at 2.051-inch intake and 2.016-inch exhaust.

The big port Apache head flows almost 340 cfm. The beer-barrel shaped intake manifold is lightweight plastic and features an angled, single-inlet throttle body mount. It also has variable valve timing (VVT). One interesting feature of the Gen III Hemi engines was that they all had windage trays that were designed as part of the oil pan gasket rather than as three pieces with a separate tray and an oil pan gasket on top and bottom.

The 6.2 Supercharged Hellcat/Demon

The Hellcat was introduced in 2014–2015 and became Chrysler’s first supercharged engine. The Hellcat engine was similar to the 6.1L and 6.4L Hemis. It used a cast-iron block with a 4.09-inch bore, which was the same as the 6.4L 392. It also used the 6.1L’s 3.58-inch stroke. This made the engine a 6.2L version at 378 ci. The engine was rated at 707 hp and 650 ft-lbs of torque, the highest horsepower rating for any production engine. The Hellcat blocks were painted orange.

The Hellcat used a similar cam as the 392 with a 0.571-inch lift, but it had 8 degrees fewer intake duration and 16 degrees more exhaust duration. The twin-screw supercharger was built by IHI Turbo America and displaced 2,380 cc. The boost pressure was electronically regulated to 11.6 psi. The supercharger was driven by the serpentine drive belt and the aluminum heads used smaller valves than the 392 engine. It maintained the long valves and tall installed height.

When the Hellcat was introduced, no one thought that this production output level could be matched because racing and custom builds have unique emissions and warranty situations that relate to production engines. Many felt that if it was going to be topped, it would only be by 10 or 20 hp. That held true for a couple years, and then the 2017 Demon burst on the scene with 840 hp! The Demon uses the same basic 6.2L engine as the Hellcat, but the supercharger is larger on the Demon at 2,900 cc and 14 psi boost pressure compared to the Hellcat’s 2,380 cc with 11.8 psi.

The dual-plug feature of all Gen III Hemi engines is easier to see with the valve cover removed. The tops of the twin spark plug towers for each cylinder look like a figure-8 on its side. You can also observe the two rocker shafts (intake at the top), which are a feature of the Hemi-head design.

Family Identification

The quick and easy way to distinguish the Gen I Hemi engines from the Gen II engines was to look at the distributor. The Gen I had the distributor at the rear, while the Gen II had the distributor at the front. This can be seen even in the bare blocks. The Gen III doesn’t use a distributor, but this isn’t obvious at first glance.

If you are used to looking at bare Gen II Hemi blocks, a bare Gen III Hemi block will most likely look small. Based on the block’s bore centers, it is actually the size of a small-block. In its normal position, the block’s pan rails sit square to the floor because of the skirted design. The most unique feature of the Gen III Hemi V-8 bare block is the high-point in the center of the front face. This high point is created by the intersection of the two deck surfaces of the bare block. The front face creates the shape of a capital A. It is lovingly called the bird house. This A shape is not carried to the rear face.

If the engine is assembled, the A shape of the front face is now located behind the front cover, water pump, and all, making it more difficult to see. When assembled, perhaps the most obvious features of the Gen III Hemi are the dual spark plugs for each cylinder and the valve cover is wider than the traditional wedge-head valve cover. All of the production Gen III engines use a beer-barrel shaped intake manifold, and all Gen III Hemi engines use a serpentine front accessory drive. These last two features are not unique to the Gen III Hemi; they were also shared with the earlier 1992–2003 Magnum engines, so they are not as good to use as identifiers.

All of the naturally aspirated production Gen III Hemi engines use a long-runner tuned intake manifold. The longer runners give better low-speed torque and are suited to street applications. All of these manifolds gain the long runners by rounding the ends into a round, beer-barrel shape. Note that the manifold flange is cut off parallel to the ground (horizontal). Shown is the 6.1L cast-aluminum intake.

The Gen III Hemi engines all use a serpentine belt for the front accessory drive. In this system, there are two idlers. A race crate motor system is shown here. The main difference is the large pulley at upper right for the power steering will be much smaller and a different length belt will be on the production versions.

Unique High-Tech Features

Many of the unique high-tech features of the Gen III Hemi engines are not visible externally. In this section, I cover internal leading-edge high-tech features of the Gen III Hemi engines including the six-bolt head pattern, multi-displacement system (MDS), multi-point injection (MPI), variable valve timing (VVT), and more.

The six-bolt head-attaching pattern is one of the unique features of the Gen III Hemi engines, but it is not visible once the engine is assembled. There are four large (M12) bolts around each cylinder and two smaller (M8) bolts at the top outside of the tappet bay. The five small bolts form a line across the top. The big bolts form two lines: one just above the cylinder bores and one just below. Also visible at the bottom are the five cross-bolts for the cross-bolted main caps.

Six-Bolt Head Bolt Pattern

All of the production Mopar small-blocks used a four-bolt head pattern around each cylinder bore. The Gen II Hemi or 426 (along with the 383s and 440s) used five bolts around each bore. In the late 1990s, Mopar Performance introduced the six-bolt head pattern on the race aluminum small-blocks and many of the R3 and R4 cast-iron race blocks.

The Gen III Hemi engines also used a six-bolt pattern around each cylinder, but the six-bolt Gen III Hemi pattern is not the same as the six-bolt race small-block pattern. The Hemi pattern used four large bolts around each chamber and two additional small bolts along the top. These two smaller bolts are in a line directly above large bolts because the block extends upward to cover the tappet chamber. This surface provides anchors for the bolts and increased stiffness for the block itself. The technology is similar to the race pattern, but the Hemi pattern provides stiffer parts and stiffer, stronger assemblies.

Not all Gen III Hemi engines use the multi-displacement system (MDS) feature, but they are all machined for the four MDS solenoids (two at the bottom and two at the top). Here the solenoids have been removed. The tappet chamber is sealed, which means there are no front or rear china walls.

This cutaway model of the Gen III Hemi allows you to see the cam and tappets, which you couldn’t see otherwise. The top of the block and three of the four head bolts are visible along with the two extra small head bolts. (Photo Courtesy FCA US LLC)

Multi-displacement System (MDS)

The multi-displacement system (MDS) system drops four cylinders when the engine is under light throttle (steady speed). MDS is operated by four solenoids located in the tappet chamber cover. These solenoids are controlled by the engine control module (ECM) or computer, which is the same computer that controls the fuel and spark.

This cylinder drop is accomplished when an oil stream to four intake and four exhaust roller tappets pushes a pin in the lifters, allowing them to compress rather than move the pushrod. The tappets can be reactivated within 40 milliseconds if the accelerator is pushed. Because of this ultra-quick response time, the switch in either direction (four to eight or eight to four) is undetectable from the driver’s seat.

Cross-Bolted Mains

Similar to the multi-point injection (MPI) feature, cross-bolted mains are not new. The center three mains on the Gen II blocks were cross-bolted. The Gen III engines’ unique feature is that all five mains are cross-bolted. Chrysler racing and Mopar Performance added this feature into the second and third redesign of the Gen II cast-iron blocks in the late 1990s. This added stiffness seemed to help make the blocks stronger.

All of the Gen III Hemi engines are cross-bolted on all five mains. Here the heads of the bolts are visible just above the pan rail. The typical main cap has two vertical main cap screws, while the aluminum block and some modified BG cast-iron blocks have four verticals bolts along with the cross-bolts. The Gen II 426 engines used cross-bolts on the center three mains.

Variable Valve Timing (VVT)

The VVT package was introduced in 2009 and continues in current production 6.4Ls. The VVT engine has the top of the A or birdhouse moved forward about 0.600 inch to line up with the new front cover to add the extra oil passages, allowing the computer to advance or retard the camshaft’s centerline. The cam is also about 0.550 inch longer and about 0.180 inch larger in diameter for the number-1 bearing only.

The heart of the VVT system found on many of the 2009 and newer Gen III Hemi engines is the cam phaser, which attaches directly to the cam sprocket. It is about 1/2 inch thick.

All of these changes are required for the additional oil passages needed to operate the cam phaser, which is the heart of the VVT package. The cam phaser is mounted to the front of the cam sprocket. The operating solenoid is in the top of the A. The phaser changes the installed cam centerline by closing the intake valve relative to bottom dead center (BDC) and opening the exhaust valve closer to BDC.

High Cam Position

The camshaft in the Gen III Hemi engines is very high; almost 1 inch taller than the Mopar A-engine small-block, which was one of the highest production engines. This high cam position helps with stroker engines by increasing the clearance between the crank and rods and the cam. By moving a cam closer to the valves, the pushrods are shorter, which makes the valvetrain lighter. A lighter valvetrain means less loads, less wear, and less potential breakage. All of these items are important for rebuilding.

One aspect of the high cam position is that the tappets are almost flat after being raised 15 degrees on each side, which means that the valve spring loads oppose each other and tend to cancel each other out and not deflect the cam lobes. Add to this that the Gen III engines use cams bearings with a larger diameter, and the larger journals mean stiffer cams and less deflection. None of these features is much of a concern at a rebuild except that production engines took advantage of these features and pushed the Eagle and Apache engine’s valve lift to 0.571 at the valve. If this high-lift approach had been used on earlier valvetrains, problems would have occurred in the warranty area and created much more work and expense at rebuild time.

Multi-Point Injection (MPI)

Multi-point injection (MPI) is not new. It was used on the 1984 2.2 Turbos and on all the 1992–1993 and newer Magnum 5.2L and 5.9L V-8s. Chrysler also experimented with crank-trigger ignitions based on a 4-tooth blipper wheel added to the nose of the crank in front of the damper on the Gen II 426 Hemi in the 1970s.

What is unique about the Gen III crank-trigger system is that the crank wheel is located inside the crankcase next to the number-8 crank counterweight. Initially, these Gen III Hemi crank wheels had 32-teeth, and now they have 58-teeth.

Oil Returns and Windage

Chrysler engineers found in the early 1960s that the crank and rods spinning around in the block’s crankcase had windage losses, which translates into lost horsepower. To solve this problem, they created a piece of fancy sheet metal that fit between the bottom of the block and the oil pan, called a windage tray. It was worth about 16 hp.

This windage tray tip was used with the Max Wedge engines in the early 1960s and was carried over to all of the Gen II 426 Hemis. It was also used on the high-performance 440s. Today’s Gen III Hemi engines all have a windage tray with integral gasket. These Gen III trays are made as part of the oil pan gasket and are sprayed on the top and bottom sealing surfaces. Each crank also has a unique tray assembly.

Engine Swapping (Packaging)

The sizes of the engine and engine compartment, known as packaging, is something that the Chrysler production engineers must consider, but it is generally not a concern in a rebuild. However, if you plan to swap the engine instead of rebuild it, then packaging is very important. Remember that the Gen III Hemi engines are basically a small-block if you look at them as width, length, and height. They are also light in weight similar to a small-block.

Although the trend began a couple years earlier, supercharged engines have jumped into the production scene and are very popular with hot rodders. This is a Whipple supercharger on a 354 Gen III Hemi Drag Pak designed for drag racing, and it is offered as a crate engine by several aftermarket engine builders. There are several aftermarket supercharger manufacturers that offer kits, and several dealers offer similar crate engines based on other superchargers and other engine displacements.

Supercharged Engines: Hellcat and Demon

The Hellcat makes 707 hp and 650 ft-lbs of torque, while the Demon makes 840 hp and 770 ft-lbs of torque. The Hellcat uses a 2.38L IHI Turbo America supercharger, while the Demon uses a larger 2.7L IHI Turbo America supercharger. Additionally, the Hellcat uses 11.8-psi boost pressure and the Demon uses 14.5-psi boost.

These production supercharger systems have the supercharger in the center with a small, basically square intercooler mounted on each side. The intake manifold integrates the supercharger and the two intercoolers to deliver the cooler, pressured air to the cylinder heads. These high-performance engines are too new to be considered for rebuilding, but I will try to cover the main aspects for future reference.

Aluminum Block

The Gen III Hemi aluminum block is a nonproduction part, but it is the block used in the 426 Drag Pak engine and the 362 oval track engine, along with being optional (in 2017) on the 354 supercharged drag engine. You would not ordinarily find an aluminum block in a rebuild. However, if your rebuild happens to have a broken block, it is nice to know that there is a stronger, aluminum block available.

Since the aluminum block uses sleeves, it can be used to service all of the Gen III engine displacements by changing sleeves. This is typically done by the manufacturer.

An aluminum block from Prefix (formerly Arrow Racing Engines) is available for the Gen III Hemi engines and is offered in several cylinder bore sizes. While it is not likely to be the original block in a rebuild, it may offer an upgrade for a rebuild that has a seriously damaged cast-iron block.

Chrysler and Mopar Performance has just introduced an all-new aluminum block designed for use with the VVT-style hardware called 6.4L timing drive. It also has siamesed-bores that allow larger bores and crankcase modifications for longer strokes.

The Foundation Block

For any engine project, rebuild or otherwise, you must have a usable block as the foundation. Taking an engine block out of a new car or truck can be expensive. As a general rule, I recommend rebuilding any engine that has come out of a crashed car or a salvage yard. If a block is damaged, as in windowed, it would have to be welded to repair. Whether welding in a patch would be feasible or not must be determined by your machine shop.

When you open the hood of a new car or truck, you are often faced with a large cover that hides the actual engine. Other models have two smaller covers over the valve cover area. These styling covers are mounted to two round push-on posts per side. The push-on posts are attached directly to the valve covers. You can’t see the actual engine or valve covers until you remove these covers. (Photo Courtesy FCA US LLC)

Short Blocks and Bare Blocks

If a block can’t be repaired, one approach is to use a new bare block or a short block. For the 5.7L and 6.4L Gen III Hemi engines, these parts were serviced a few years ago. Only a couple dealers were still listing them at this writing. Consider using a long block if these are not readily found.

Long Blocks

With new short blocks and bare blocks being in short supply, the next reasonable approach is a long block. Long blocks include heads but do not have the intake, front cover, valve covers, or oil pan. With a long block, one part number gets you a lot of parts and is a much better approach than ordering them one at a time.

Long-block assemblies should be available at Chrysler dealers. While prices may vary, purchasing a long block is not as expensive as buying a fully assembled crate motor. In the chart on the next page, I have listed some currently available long blocks that might be useful in a short-on-parts rebuild project. I picked the oldest and most popular engines (the 5.7 and 6.1) because they are the ones most likely to have worn-out parts. The dealer will have more versions available.

The largest piece of any engine rebuild and the foundation for your project is the actual engine block. The disassembly process gets down to the bare block, where all five cross-bolts are removed. At this point, the block can be sent to your machine shop and inspected for wear and usability. You cannot tell what is going to be required until this initial inspection is complete.

Head Assemblies

In a general rebuild project, you may have a failed engine that hurt the block, but you may also have a good block with a wounded head. You may also have found a usable bare block or a short block that needs heads. Once you have a usable block, you might need heads or want a spare set of heads. Similar to the block assembly approach, you can save time and money by ordering one part number rather than buying the head, valves, and springs separately. Keep in mind that Gen III Hemi production engines use a different head on the left and right sides and all head assemblies include valves and springs. The chart on the next page lists head assemblies available from Chrysler dealers for the long blocks in the previous section.

Tech Tip

Chrysler dealers, Mopar distributors, and many engine builders offer their own crate motors that may vary in specific details and performance ratings from some of the factory hardware. The new Mopar Performance 6.2L Hellcat crate engine should be very popular in 2018. There are several performance dealers offering supercharged 392 engines using the Magnuson supercharger that look very similar to the Hellcat. The 354 Drag Pak crate engine uses a Whipple supercharger, which also looks similar. ■

Crate Engines

The Chrysler crate engine options are constantly evolving. The 5.7L, 6.1L, and the 6.4L 392 have all been offered as crate motors dating back to the initial Gen III Hemi introduction in 2003. Specific details of the crate engines change frequently based on customer demand and parts availability. Today, the 5.7L Eagle and 6.4L 392 Apache engines are available as crate motor assemblies. The part numbers and performance ratings are listed below. Beginning in 2018, Chrysler’s Mopar Performance will also offer a 6.2L Hellcat Crate engine.

If you had a basic engine explosion or the inspection showed the block to be broken, a crate engine can be a possible solution. One part number gets you all the parts for the swap. This modified Hellcat crate engine may be just what you need. There are also 5.7L and 392 crate engines available. (Photo Courtesy FCA US LLC)

* The 5.7L crate engine rated at 383 hp replaces earlier 5.7L crate motors that were rated around 370 hp.

** The 6.4L crate engine above rated at 485 hp replaces an earlier 6.1 L crate motor that was rated at 425 hp and earlier versions of the 6.4L engine.

Specials
Year	Engine	Note
2014–2017	354	The 354 is a race only package.
2017–2018	362	The 362 is a circle track crate engine offered by Prefix based on a sanctioning body specced carburetor and distributor.
2013–2018	426	The 426 aluminum crate engine was offered by Mopar Performance (MP) but intake availability caused supply problems, and it is not currently offered by MP. However, aluminum 426 crate engines are still offered by Prefix offer several variations with the max power package (big cam, big/tall intake, big 4-barrel throttle body) coming in around 780 hp. The large cam and tall intake used on this version may not be suitable for all applications. More streetable versions may be in the 600-plus-hp range.