Engine
EngineCylinder Block
The 3.5L & 4.2L engine consists of an eight cylinder 90 degree 'Enclosed V' configuration liquid cooled aluminum cylinder block with dry cast liners.
Viewed from the driving position, the right-hand cylinder bank is designated A-bank and the left-hand cylinder bank as B-bank.
Cylinder Block Drain Plug
The coolant drain plug is located on the rear left side of the cylinder block.
On vehicles supplied with a cold climate package (i.e. vehicles operating in conditions regularly below -30°C) a cylinder block heater unit is fitted instead of the drain plug.
Knock Sensors
Two knock sensors are fitted to the cylinder block on the inboard side of each cylinder bank. The electrical connector of each sensor is secured to the left-hand engine cover bracket.
These piezo-electric sensors provide inputs to the engine control module (ECM) to indicate the detection and location of detonation during combustion.
Crankshaft
The cast iron crankshaft has undercut and rolled fillets for improved strength and six counter-balance weights make sure low levels of vibration from the four throw, five bearing configuration.
The main bearing shells are aluminum/tin split plain type. An oil groove in the top half of each bearing transfers oil into the crankshaft oilway drillings for lubrication of the connecting rod bearings. A lead/bronze thrust washer is fitted on each side of the top half of the center main bearing.
The crankshaft rear oil seal is lipped and is a press fit in the interface of the bedplate to cylinder block. A torsional vibration crankshaft damper pulley is bolted to the front of the crankshaft.
Connecting Rods and Pistons
The connecting rods are manufactured from sinter-forged steel and have fracture-split bearing caps. The opposing sides of each connecting rod being fractured at the bearing horizontal center line.
The cylinder position is etched on adjoining sides of the joint to identify matching connecting rods and bearing caps. The connecting rod bearing shells are lead/bronze, split plain bearings.
The pistons are open ended skirt design with small recesses for valve clearance and flat upper surfaces to reduce heat absorption. Three piston rings, two compression and one oil control, are fitted to each piston. Each piston is fitted on a gudgeon pin which is in a lead/bronze bush fitted in the connecting rod.
Timing Gear
Multi link primary and single link secondary chains drive the camshafts of each cylinder bank. The primary chains transmit the drive from sprocket on the crankshaft to a sprocket on each intake camshaft. The secondary chains transmit the drive from a second, smaller sprocket on the intake camshaft to a sprocket on the exhaust camshaft.
Each chain has a hydraulic tensioner operated by the engine lubricating system. A jet of oil from the end of each tensioner lubricates the chains. The primary chain tensioners act on pivoting flexible tensioner blades, the secondary chain tensioners act directly on the chains.
A woodruff key locates the drive sprocket on the crankshaft and these are retained in position by the crankshaft damper pulley.
The variable valve timing (VVT) oil control unit and the exhaust camshaft sprockets are non-interference. They are clamped in place on the camshafts by the retaining bolt and clamping plate/washer.
Timing Cover
The aluminum-alloy timing cover accommodates the crankshaft front oil seal. Poly-acrylic seal in-groove gaskets seal the joint between the timing cover and the front face of the engine.
Cylinder Heads and Valve Gear
Cylinder heads are unique to each cylinder bank and are secured, using deep seated bolts, to the cylinder block. Two hollow dowels align each cylinder head with the cylinder block.
Each cylinder head gasket consists of a silicon beaded composite gasket with metal eyelets for the cylinder bores.
Each cylinder head incorporates dual overhead camshafts operating four valves per cylinder via solid aluminum-alloy valve lifters. A steel shim in the top of each lifter allows adjustment of valve clearances.
Collets, valve collars and spring seats locate the valve springs on the intake and exhaust valves. Valve stem seals are integrated into the spring seats. Four 14 mm spark plugs are located in a recess on the center-line of each cylinder head. Refer to Ignition System.
Camshafts
The chilled cast iron camshafts are each retained by five aluminum alloy caps - location numbers 0 to 4 for the intake camshaft and 5 to 9 for the exhaust camshaft from the front. A machined flat near the front of each camshaft enables the camshafts to be locked during the valve timing procedure.
Camshaft Sensor
The camshaft sensors are fitted to the rear of each cylinder head and are triggered by four toothed sensing rings fitted to the rear of the intake camshaft. The camshaft sensors are variable reluctance sensors that provides an input to the ECM of intake camshaft position.
Camshaft Covers
The valve covers are made from thermoplastic plastic; the right-hand bank cover incorporates an outlet for the part load engine breather.
The left-hand bank cover incorporates the engine oil filler cap and an outlet for the full load engine breather. Identical oil separators are incorporated inside the top of each cover. Each oil separator comprises a wire gauze packing in an open ended enclosure below the breather outlet.
Bedplate
This is a structural casting bolted to the bottom of the cylinder block to retain the crankshaft and to further improve overall rigidity.
Main bearing clearance changes due to expansion are minimized by means of iron inserts cast into the bedplate main bearing supports. Two hollow dowels align the bedplate with the cylinder block and the joint is sealed by a continuous bead of sealant.
Engine Mountings
The engine is mounted at two points. At each side of the engine, there is a mounting bracket with a hydraulic mounting to the subframe.
Engine Lubrication
Oil is drawn from the reservoir in the oil pan and pressurized by the oil pump. The output from the oil pump is then filtered and distributed through the internal oil passages. Where an oil cooler is fitted, the oil is cooled before entering the filter.
All moving parts are lubricated either by pressure or splash oil. Pressurized oil is also provided for operation of the variable valve timing units and the timing gear chain tensioners. All of the oil system components are installed on the structural sump.
Oil is returned to the oil pan under gravity through large drain holes in the cylinder heads and the engine block to make sure quick return of the oil.
Oil Pick-Up
The plastic molded oil pick-up is attached to the underside of the structural sump. It is immersed in the oil reservoir to provide a supply to the oil pump during all normal vehicle attitudes. A castellated inlet allows the supply to be maintained after any deformation of the sump pan (e.g. after grounding). A mesh screen in the inlet prevents debris from entering the oil system.
Oil Pressure Switch
Installed at the right front of the structural sump, the oil pressure switch connects a ground input to the instrument cluster when oil pressure is present. This switch operates at a pressure of 0.15 to 0.41 bar (2.2 to 5.9 lbf.in2).
Oil Pump
The oil pump is fitted at the front of the engine and is driven directly by the crankshaft. The inlet and outlet ports align with oil passages in the bedplate, with a rubber coated metal gasket to seal the pump to bedplate interface.
An integral pressure relief valve regulates pump outlet pressure at 4.5 bar (65.25 lbf.in2).
Oil Pan
The oil pan/sump comprises an aluminum-alloy structural sump bolted to the bedplate and a pressed steel pan with integral sump plug, bolted to the structural sump.
Oil Filler Cap
The oil filler cap is located on the top of the left-hand bank valve cover.
Windage Tray
A windage tray attached to the top of the structural sump isolates the oil pan from the disturbed air flow, caused by the rotation of the crankshaft; preventing oil aeration and improving oil drainage.
Crankcase Ventilation
The engine is ventilated through a part-load and a full-load breather; one on each valve cover. These flexible plastic hoses incorporate O-ring seals and quick release connectors.
The part-load breather ventilates the left-hand valve cover (B-bank) and feeds onto the throttle body adaptor and the purge valve. This breather is connected between the oil separator in the cover and the induction elbow.
The full-load breather ventilates the right-hand cover (A-bank) and is connected between the oil separator in the cover and the air intake duct between the mass air flow (MAF) sensor and the throttle body.
The MAF sensor unit combines the two sensors: one for air flow and one for air inlet temperature. It is a hot wire sensor that provides an input which is (approximately) proportional to the mass air flow into the engine.
Each valve cover oil separator consists of wire gauze packed into an open ended enclosure in the top of the cover, below the breather outlet.
Variable Valve Timing (VVT)
The variable valve timing system improves both low speed and high speed engine performance, engine idle quality and exhaust emissions. It is an infinitely variable system operating on the intake camshafts only. There is the equivalent of 48° of crankshaft movement between the retarded and advanced positions. Engine oil pressure operates the system under the control of the ECM.