New Hemi Engines 2003-Present. Larry Shepard

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       With any engine family, there are engine builders, head specialists, and parts retailers/wholesalers that specialize in the new hardware, such as Modern Muscle Xtreme (MMX). MMX had a Gen III Hemi parts and vehicle display at the 2017 Performance Racing Industry (PRI) trade show.

      The Gen III Hemi development started slowly in 2003. The 5.7L Hemi engines delivered a modest 345 hp and received many awards in the first few years. A key reason for the slow development was that the company was downsizing leading up to the Chrysler bankruptcy in 2008. Chrysler and the Gen III started to gain some momentum in 2009–2010 with the SRT models and with the Challenger Drag Pak cars.

      In 2009, the Eagle 5.7L was released with an engine rated at 385–390 hp, which is a pretty good gain for an existing production engine! It is an easy engine to build and is durable, lightweight, relatively small, and responds easily to performance changes.

      Chrysler’s production engineers took another, even bigger leap forward from a performance standpoint in 2011. By earlier standards, the 6.4L 392 could be considered close to a race engine with its high compression ratio (10.7:1), high valve lift (.570 inch), big valves (2.14 inch), and high-flow ports (around 330–340 cfm intake stock and more than 400 cfm ported). The 485 hp in full production/emission trim and the 1.23 hp/ci would seem to support this somewhat wild comparison. For whatever reason, all of this 392 magic and high-tech features slid in under the radar, but this high-performance package is basically ready to go racing!

       Hot Rodding

      The term hot rodding covers a lot of ground and could be a street rod, street machine, custom build, or one of several other options. Hot rodding began in earnest in the 1950s and 1960s and tended to focus on engine swapping, such as installing a V-8 in place of a production 4- or 6-cylinder engine, installing a big-block V-8 in place of a small-block V-8, or better yet, installing a Hemi in place of any engine! In the 1970s, 1980s, and 1990s, hot rodding seemed to go in other directions. These markets wanted a unique vehicle, and engine swapping was an easy way to obtain this goal. The Gen III Hemi engine appears to fit this market perhaps better than any earlier engine because of its unique combination of smaller size, Hemi heads, lighter weight, and huge horsepower availability.

       There are many types of hot rods. One of the more popular combinations is the Gen III Hemis in early B- and E-body Chrysler products. There are motor mounts, headers, and oil pans made for this swap than any others. Shown is the 392/426 Gen III Hemi in a 1968 Charger (B-body) chassis.

      In the late 1990s and early 2000s, the hot rod market began moving in the high-tech direction with fuel injection or MPI being popular. In the last 7 to 10 years, these performance customers are moving away from using the MPI system and are now trying Holley or Edelbrock carbs or one of the many new throttle body–style fuel-injection systems now available. In any case, with MPI or with a carburetor/distributor, the basic engine will probably need to be rebuilt.

       If you are going to build a custom car or hot rod, you will need an engine assembly to rebuild and install in your special project. There are millions of Gen III Hemi truck engines, and they may look somewhat unique, such as this vertical throttle body mount and can easily be converted. (Photo Courtesy FCA US LLC)

       Rebuild

      The key word in this book is rebuild, because that is what we want to do! Rebuild is generally a verb and means “to build again” or “build over.” You might say that it means that you take it apart and put it back together again. Close but not quite! Actually, you take a used engine assembly apart, replace the worn parts, and put it back together again. There are a lot of shades of gray to this sentence, and I will try to cover as many as possible while trying to keep the goal of rebuilding the engine in focus.

       Because the Gen III Hemi is shorter, narrower, and much lighter than earlier Hemis, it makes a great engine swap choice (an A-body shown). The close shock towers presented a problem for the Gen II Hemi and RB big-blocks. (Photo Courtesy Bob Wilson)

      The special features of the Gen III engines (active intake manifold, multi-displacement system, and variable valve timing) are not the main focus of this book, but I will discuss them in general terms so that you can understand what it is and how to remove and install the unique hardware.

      One of the special features of all Gen III Hemi production engines is multi-point injection (MPI). The basic MPI system was introduced on the 4-cylinder engines (2.2 turbo) in 1984 and was on all of the production vehicles with the introduction of the 1992–1993 Magnum V-8 engines (5.2L and 5.9L). One of the key tech features of all MPI systems is the group of 10 sensors that feed engine information to the engine’s computer. It is very important that you become familiar with where these sensors are and what they do. Most of these sensors will be disconnected at engine removal and must be reconnected when the rebuilt engine is reinstalled. Most of these sensors do not have to be removed from the engine part that they are installed in (the throttle body has three, the intake has one, etc.), but the one installed in the block (crank position sensor) must be removed once the engine is on the stand. If not, it could be damaged in all the machining operations that the block goes through.

       With the valve cover removed, it is easy to see the dual-plug towers or stands. The intake (upper) and exhaust (lower) rocker shafts are also visible, along with the highly angled rocker arms.

       The Gen III Hemi engines feature tuned intake manifolds. Tuned intakes were first developed on the late 1950s big-block wedges and the original Gen II 426. These early versions tended to have multiple carbs. The longer runners in the Gen III are accomplished by curling the runner over to create a beer-barrel shape. Note that the runner enters the head at a perfect flow line to match the intake port. The 6.1L Hemi is shown with its aluminum intake; the 5.7L and 6.4L use similar plastic intakes. (Photo Courtesy FCA US LLC)

      When rebuilding, you will want to follow the advice of Hemi specialists. You could define a specialist as an expert on a particular engine family, in that he or she builds lots of them, or has been doing it for years, or, in many cases, all of the above. Engine builders or engine specialists generally are divided into General Motors, Ford, and Chrysler specialties. The Chrysler specialists are often divided further into Hemi engine builders, A small-block engine builders, and RB and B big-block builders. The Gen III Hemi engines are creating their own specialists to add into this mix.

      These engine specialists also develop products to take performance a step or two further. The aftermarket’s role in the basic Gen III Hemi engine development is just beginning, but there are already many options for hardware for your rebuild. With the factory hot rods at 707 hp (Hellcat) and 840 hp (Demon), the naturally aspirated versions will not be far behind as parts and performance packages become readily available. The maintenance and service sides of the aftermarket have been readily available since the introduction of this new engine family, so parts availability should not be an issue with any Gen III Hemi rebuild project. I will address as many of them as I can throughout our rebuilding process.

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