In 2008, the 4.7L PowerTech has undergone significant changes. In 2005, the base version also got two knock sensors and other minor changes. version was replaced by a 5.7L V8 Hemi, but for some models, it was being offered until 2008. In 2005+ Jeep Grand Cherokee, the 4.7L H.O. This engine has an additional 30 horsepower and 35 lb-ft of torque over a basic engine. The 4.7L V8 HO features a 9.7:1 compression ratio, high-compression domed pistons, two knock sensors, new camshafts, and tuned intake. In 2002, Chrysler introduced a "High-Output" version of the 4.7L PowerTech engine as an option for the Jeep Grand Cherokee Limited and standard for the Overland models. The 4.7 V8 engine also features a modern coil-on-plug ignition system and a hybrid cooling fan system (in-line electric and engine-driven fans). The diameter of the throttle valve is 2.56 inches (65 mm). The engine speed is controlled by an electronic throttle body (fly-by-wire). The new tuned-length runner intake manifold is made of polymer material. The fuel injectors are mounted to the intake port in the head. The engine has an electronic fuel injection system (sequential multi-port injection). On top of each cylinder head, there is a cast magnesium valve cover. Camshaft specifications: the valve lift is 0.443 inches on the intake and 0.429 inches on the exhaust, the duration is 244 degrees intake and 254 degrees on the exhaust. The valvetrain is equipped with hydraulic lash adjusters. The diameter of intake valves 1.89 inches (48 mm) and the exhaust valves are 1.46 inches (37 mm). This configuration allowed to make the shape of the combustion chamber and the arrangement of spark plugs more efficient (almost hemispherical chambers). Intake and exhaust valves are pushed apart, and rocker arms are turned by 180 degrees relative to each other. Each cylinder head has only two valves per cylinder and one top-mounted, chain-driven hollow camshaft (SOHC design). Between each head and engine block, there is a three-layer laminated stainless steel gasket. The engine is equipped with cast aluminum alloy cylinder heads. While the 3.7L V6 has a balancing shaft, the 4.7L engine doesn't need it. From underneath, the crankcase is sealed by a stamped steel oil pan. This engine has powder-forged metal, fracture-split connecting rods (the length is 6.12 inches/155.5 mm) and cast aluminum pistons with moly coated skirts. The bedplate made of compacted graphite iron adds rigidity to the block and reduces noise and vibration. The debuted engine was fitted with a nodular cast-iron crankshaft, which is attached to the block by using a single bedplate instead of five individual main-bearing caps. The engine block was designed from scratch and all dimensions are new. The 4.7L PowerTech has a cast-iron cylinder block with a 4.09 inch (104 mm) bore spacing, a 9.09 inch (231 mm) deck height, and a 90-degree angle between cylinder banks which is optimal for using one crankpin journal for a pair of connecting rods.
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