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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