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
