New Hemi Engines 2003-Present. Larry Shepard
The clear, square plastic plate with a hole in it (middle left) is used to seal the chamber and allow it to be filled with fluid. The CC-ing fluid (rubbing alcohol) and food coloring (red) are in the upper left. The bridge and dial indicator are used to measure the piston drop if a dished or domed piston is used. The degree wheel and the pointer are used to centerline the camshaft. In the lower right, there is a small, L-shaped piece of coat-hanger. It was cut and bent to size. It is used to hold the camshaft tensioner back away from the chain during disassembly. It will stay there until the engine is reassembled.
Extra Precision Tools
There are few do-it-yourself projects outside of engine building that require precision in the 0.001-inch area. Extra precision tools are as follows:
• Dial indicator with magnetic base
• Bridge with dial indicator
• Depth micrometer or ring squaring tool
• Dial bore gauge (optional)
• 0-1-inch, 1-2-inch, 2-3-inch, 3-4-inch, and 4-5-inch micrometers
• Snap gauges
• Dial/Vernier calipers
• Valve spring tester (optional)
• gram scale (optional)
Work Space
You will need to prep your work space for disassembly of the engine. Remember that the engine is large, and it takes up more space as you take it apart. Spend some time planning where you will place the two heads, the crankshaft, the intake manifold and its hardware, the valve covers, and eight piston-and-rod assemblies.
Vehicles can weigh 3,000 to 5,000 pounds with the engine alone weighing 400 to 600 pounds, so safety must be your top priority to avoid injury. Get jacks and jackstands lined up and decide on a transmission support as you plan your project. Also gather wheel chalks to keep the vehicle from moving until you want it to.
Also remember that you will be working with gas and oil and you need to use extra caution. Keep a fully charged fire extinguisher handy, and any oil or gas removed from the engine or used during assembly should be properly recycled.
For precision measurements, you will need a selection of micrometers: 0–1 inch, 1–2 inch, 2–3 inch, 3–4 inch, and 4–5 inch. The snap gauges (upper right) are used with the micrometers to measure inside diameters, while the micrometers themselves measure outside diameters. The diameter of the 392 piston (4.09 inches) would use the 4–5 micrometer. The diameter of the cylinder bore that the piston came out of is transferred to the snap gauge and then measured by the micrometer.
If you are going to inspect the engine parts, you are going to need a dial indicator along with a magnetic base (left) and a bridge (right). You can use one dial indicator and switch from one mount to the other, but I prefer to have two separate tools.
If you plan to measure the cylinder bores, you will need a dial bore gauge (top). This step is often left to the machine shop. The depth micrometer (bottom) is used to set the ring height in the cylinder bores when you want to gap the rings (measure the end gap).
Multi-Point Injection (MPI)
The multi-point injection (MPI) system is easy to work with, especially the factory system that is used on all of the Gen III Hemi engines. A basic rebuild would use the same sensors, so it is mainly identifying and protecting the existing sensors. It can be more complicated if you are making a conversion or a custom installation. For example, if you install a 2003 Gen III Hemi into a 1968 B-body, then you must take all the MPI hardware (sensors, wiring, etc.) with it. That style of engine swap is not as easy as installing a 1968 Gen II Hemi into a 1958 Chrysler product. The 1968 engine comes with a carburetor and distributor, while the Gen III engines have neither.
The basic hardware in any high-tech MPI system includes the fuel rail, injectors, the throttle body, and the intake manifold. There are also eight sensors that must all be wired in and operating for the ECM to know what’s happening with the engine so everything works properly.
Fuel Rail
With any V-8 engine, the typical fuel rail system consists of two sides and a crossover. The fuel rail assembly attaches directly to the intake manifold. There is a fuel pressure relief and a pressure regulator that have been moved from the fuel rail into the gas tank.
Once fully assembled with the entire engine harness hookup, it is hard to find the fuel rail on production engines. First, locate the two round push-on posts (middle of photo above valve cover screws) and the silver fuel rail behind them. There are three injectors visible below the fuel rail and seated into the intake manifold at the manifold face. Each injector is connected to the engine wiring harness using a red-and-black connector. Most of the production units use a hose crossover that goes across the top of the intake manifold at its middle and extends to the upper right to connect the two sides. Other versions connect across the front or rear ends of the main rails.
The throttle body is mounted to the front of the intake manifold with four screws. Two of the eight sensors that feed information about the engine to the computer are in the throttle body. The electric throttle control is at the front of the manifold (center) and the air temperature sensor is at the lower left. Unplug each one and tag them before pulling out the engine.
Injectors
For production Hemi engines, there is one injector per cylinder. Each is located at the intake manifold interface and is held in place by the fuel rail. The injectors should be removed with the fuel rail as an assembly.
Throttle Body
The throttle body also mounts directly to the intake manifold. It should be removed with the intake manifold and unassembled separately at a later time. The throttle body has several sensors attached to it, and they should be left as is unless they have failed.
Intake Manifold
The fuel rail, injectors, and throttle body stay attached to the intake manifold and are removed as an assembly once the engine is on the stand. The intake manifold and throttle body assembly hold more sensors than any other part of the engine. The sensors themselves do not have to be removed from the manifold or throttle body unless they are damaged or have failed.
Sensors
The production Gen III system has eight sensors that feed information to the computer. The aftermarket multi-point injection (MPI) units use a similar number. As you rebuild the engine, you will remove these sensors with the exceptions of the speed sensor and the O2 sensor. These sensors stay in the car if only the engine is being pulled.
The engine wiring harness stays in the vehicle. Be sure to label all wires and hoses to each sensor as it is removed or disconnected. Tag them using masking tape and black marker. All wires will tend to look the same at engine reinstall.
Crank Position Sensor: This sensor is located on the passenger side of the block at the rear edge of the number-8 cylinder. This sensor counts the number of teeth on the crank wheel (32 or 58).
Cam Position Sensor (CMP): This sensor is located on the passenger side of the front cover, and is even with the camshaft centerline.
Engine Coolant Sensor (ECT): This sensor is located in front of the