Читать книгу New Hemi Engines 2003-Present - Larry Shepard - Страница 7

INTRODUCTION

What is a Hemi? The short answer is that Hemi is short for hemispherical, which relates to the engine’s combustion chamber shape. There are several ways to group engines: size (cubic inches or liters), number of cylinders and alignment (inline-6 or V-8), and valve arrangement (flathead, wedge, or opposed).

When looking at valve arrangement, flatheads have the valves in the block. With a wedge, the valves are overhead and sit next to each other along the cam centerline. For the opposed valves arrangement, the two valves (intake and exhaust) are on opposite sides of the chamber, resulting in a chamber that looks like a hemisphere. This opposed valve layout and the typical valve angles it used became known as the Hemi.

Engine Development

In the early and mid-1950s, the Gen I engines produced the 331, 354, and 392. From 1964 to 1971, the well-known Gen II engines produced the 426. While the Gen III Hemi was an all-new engine design introduced in 2003, it takes features from both of its ancestors and adds many unique features.

The Gen III Hemi engines in production today have evolved from a long line of performance/race Hemi engines that also did double duty as production engines. These new Hemi engines shared many features with the Chrysler/Mopar small-block engines.

During the past 14 years, Chrysler engineers and mechanics have done a tremendous amount of engine development. There’s been so much testing that Chrysler has had anywhere from 10 to 100 engines running on dynos and in cars for 8 to 16 hours per day, 7 days a week, for 14 years! One of the results of this testing and development was the 2009 Eagle 5.7L engine, which increased from 345 hp to about 390 hp. Another result introduced in 2011 was the 392-ci Apache engine, which produces 485 hp in full emissions and warranty trim.

From all of their testing data and technical information, Chrysler engineers and designers took what they felt would make the best production engine for the new millennium and added special high-tech hardware, such as the multi-displacement system (MDS), variable valve timing (VVT), and the active intake manifold. These unique features and the advanced technology that go with them are just beginning to be explored by engine builders and manufacturers looking to make race cars and special performance vehicles be more competitive.

The Gen II Hemi engines use a wide, deep, or thick valve cover with one single plug in the center of the cover for each cylinder. The plug wire uses a large round seal on top of the cover, which highlights the plug location. There was a twin-plug version of the Gen II, but they are very rare. (Photo courtesy Bob Wilson)

The easiest way to identify a Hemi engine is to look at the valve cover. The Gen III Hemi engines use a fairly shallow plastic valve cover with two holes for each cylinder because all Gen III Hemi engines use dual plugs.

Engine tuning used to be set the distributor (ignition timing) and adjust or jet the carburetor. This basic approach all changed with the introduction of multi-point injection (MPI) and the engine computer. The MPI computer controls everything, including fuel and ignition, so every application and modification requires that the computer be reprogrammed or reflashed. In the mid to late 1990s and early 2000s, Chrysler developed the engine control module (ECM) for reprogramming. The carmaker sold ECMs directly to customers. This led to aftermarket performance code breakers offering the same reprogramming service. Today, the aftermarket offers handheld units that work with the production ECM and can control almost every engine function for all applications.

All Gen III Hemi production engines use multi-point injection (MPI). The MPI system uses one injection in the intake manifold port runner at the manifold face (just above the valve cover). The injectors are fed fuel from the fuel rail, which is the long tube parallel to the cam centerline that sits above the four injectors. The throttle body mounts on top of the manifold or at the front, depending upon application.

All Gen III Hemi production engines come with MPI. However, a carburetor and distributor are desired for some applications, such as hot rods, street machines, and custom builds. Prefix makes a new front cover kit for these engines that allows the use of a distributor (blue cap in upper left) and a mechanical fuel pump (used with a carburetor) mounted at the lower middle.

Horsepower Production

In the mid-1950s, the Gen I Hemi engine made almost 1 horsepower per cubic inch (hp/ci), and in 1958 its big brother the 392 was only a few horsepower short of the magic 1 hp/ci goal. The Gen II 426 Hemi was only 1 hp short of that 1 hp/ci goal in its production period through 1971. For comparison, the original Gen III 5.7L Hemi has 345 ci and was rated at 345 hp in 2003. While this isn’t a fair comparison, it illustrates that the new Gen III Hemi fits in well with the family tradition.

In the 1960s, there were only three companies that rated engines: General Motors, Ford, and Chrysler. Production engines were rated on a cold bare gross system (basically open exhaust and no accessories) and a net system, and the advertised ratings were somewhere in between. Before 1972, guidelines were just that, so any rating came with many unknowns. In an effort to improve this situation for consumers, the federal government asked the Society of Automobile Engineers (SAE) to define this engine rating system based on the new emissions regulations in 1972. The advertised rating moved closer to the net rating and the gross or cold bare gross rating went away. The switch in systems caused a big drop in the horsepower ratings for almost all engines. However, the compression ratio drop hurt the high-performance engines more because they dropped from 10.5 to 8.5 while other regular-performance engines went from 8.5 to 8.0.

Since then, government regulations have adjusted the ratings definition to more closely match the vehicle. With the new system, there is no flexibility. Government officials have been trying to get to an as-installed number, as most agree that using net ratings is misleading. Today, the system is still watched closely. There haven’t been any major revisions during the 14 years of Gen III Hemi production. This means that the rating given for your engine will be close to what you will get from the assembly when you rebuild it.

Production engines are rated in the 345-hp to 485/490-hp range with the supercharged 707-hp and 840-hp versions covering the big end. Each engine has a cover that spells out the engine or identifies it as supercharged. The covers sit on two round plugs on top of the valve covers. There are large single covers, “supercharged” and “392 Hemi” are popular, or two smaller cover versions, such as this “Powered by SRT” version. In this case, the engine’s intake manifold sits between the two covers.

The 2011 Gen III 6.4L 392 makes 1.23 hp/ci on a much tougher rating system based on emissions and fuel economy concerns. The fact that 6.4L 392 produces 485 hp is impressive for an engine that is fully emission certified, has warranties through corporate dealers, and is rated on today’s SAE regulation. It is one of the highest nonsupercharged production engines, especially of this size.

Supercharging

Supercharged engines have been in production at Chrysler since late 2014. The Gen III Hemi with a supercharger spools out some pretty big power numbers, as the 707 hp on the 2014 Hellcat and the 840-hp Demon in 2017 demonstrate. Supercharging the Hemi engine family has produced impressive results ever since the introduction of the Hemi in the 1950s.

Supercharging was popular on the early 354 and 392 Gen I engines in drag racing. These drag racing superchargers were mainly 6-71 and 8-71 blowers driven by a cog-belt off the front of the crank. Supercharging was also popular on the 426 Gen II engines, especially in modified classes such as all drag racing classes (AA/GS), Top Fuel, and Funny Car. By the early to mid-1970s, these Gen II Hemi supercharged engines were available from the aftermarket with aluminum blocks that were copied from the cast-iron production blocks.

The top of the supercharger covers the top-center of the engine in the supercharged versions. Two separate engine covers say “supercharged Hemi.” These covers offer engine customizers a great opportunity to be creative. (Photo Courtesy FCA US LLC)

The production supercharger is driven by a very wide multigroove belt that is similar to the serpentine accessory belt but is almost twice as wide. It is located just behind the radiator hose. At more than 2 inches wide, the green belt is quite obvious.

While the racing evolution of the Gen III Hemi began slowly, it began picking up speed with the introduction of the 426 Drag Pak engine. At 426 ci, it was much larger than the production engines and had an aluminum block and MPI injection with a 4-barrel throttle body that replaced the single-throttle body used in production.

Racing Evolution

In automotive history, manufacturers have often made statements that they use racing to develop better production engines. There is probably no better example of this than the Gen II 426 Hemi built from 1964 through 1971. The 426 racing engine was rebuilt a lot. This constant rebuilding of the basic hardware in a neverending quest for more performance is common in racing. The repeated rebuilding basically wore out these Gen II engines. By the early 1990s, there were also major availability issues, which were resolved in the mid-1990s when Chrysler’s Mopar Performance brought it back.

The Gen III Hemi aluminum block is a direct replacement for the original 5.7L Gen III Hemi engine, with the exception of the bore size that can vary. It is not based on the newer variable valve timing (VVT) engines that moved the front face forward to create room for the cam phaser.

Why would I mention this Gen II problem? Chrysler built about 10,000 Gen II Hemi engines and may have had another 1,000 in parts. The Gen III Hemi engine has 3.5 million units created so far, and that number is growing every day. This means that basic Gen III Hemi cores will be available to rebuild for a very long time! As a bonus, these are the numbers for production vehicles; there should be about 350 times as many racing engines to be rebuilt. Get ready to be busy!

Racing came easy to the Gen I and Gen II engines because they evolved with the various sports and racing venues. Chrysler race teams used the Gen II 426 Hemi for competition before it went into production. The Gen III Hemi started out more slowly relative to actual/official racing participation, but the production engines in many different vehicles are at a very high performance level.

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.

No matter what the end project is going to be, production or racing, you need an complete engine assembly. It could be stock or modified, fuel injected (as shown) or carbureted, vertical throttle body (shown) or horizontal (most non-truck production units). The parts are readily available to switch the engine in any of these directions.