Cylinder Head Components

CYLINDER HEAD COMPONENTS








Cylinder Heads
The cylinder heads are unique to each cylinder bank. Deep-seated bolts, to reduce distortion, secure the cylinder heads to the cylinder block. Two hollow dowels align each cylinder head with the cylinder block.

The 14 mm spark plugs, one per cylinder, locate in recesses down the center line of each cylinder head.

The engine-lifting eyes are bolted to the cylinder heads, two on the rear (one per head) and one at the front.

Camshaft Covers





The camshaft covers are manufactured from thermo-plastic. The bank 'A' camshaft cover incorporates an outlet for the part load engine breather. The bank 'B' camshaft cover incorporates an outlet for the full load engine breather and the engine oil filler cap. Identical oil separators are incorporated below the breather outlet in each cover.

Silicon rubber in-groove gaskets seal the joints between the camshaft covers and the cylinder heads. Together with spacers and seals on the camshaft cover fasteners, they also isolate the covers from direct contact with the cylinder heads, to reduce noise.

Cylinder Head Gasket
The multi-layered steel cylinder head gasket has cylinder specific water flow cross-sections for uniform coolant flow.

Camshafts





The camshafts are manufactured in chilled cast iron. Five aluminum alloy caps retain each camshaft. Location numbers, 0 to 4 for the intake camshaft and 5 to 9 for the exhaust camshaft, are marked on the outer faces of the caps.

Sensor Ring








Timing rings for each camshaft position sensor are located at the rear of both intake camshafts. A flat, machined near the front of each camshaft, enables the camshafts to be locked during the valve timing procedure.

Camshaft Position Sensor





The camshaft position sensors are installed in each cylinder head at the rear of the intake camshaft. It is a variable reluctance sensor that provides an input to the ECM regarding the position of the camshaft.

Inlet and Exhaust Valves
Each cylinder head incorporates dual overhead camshafts operating four valves per cylinder via solid shimless aluminum alloy valve lifters.

The lightweight valve gear provides good economy and noise levels. Valve head diameters are 31 mm (1.220 in) for the exhaust and 35 mm (1.378 in) for the intake. All valves have 5 mm (0.197 in) diameter stems supported in sintered metal seats and guide inserts. Collets, valve collars and spring seats locate single valve springs on both intake and exhaust valves. Valve stem seals are integrated into the spring seats.

CAUTION: Due to slight variations in length, the valves are not interchangeable between marques (Land Rover, Jaguar and Aston Martin).

Fuel Injectors





Eight, top fed, eight hole, fuel injectors are installed in the fuel rails. The injectors are electromagnetic solenoid valves controlled by the ECM. Two O-rings seal each injector to manifold interface. The fuel jets from the injectors are directed onto the back of the intake valves.

VARIABLE VALVE TIMING (VVT)
The continuously VVT unit turns the intake camshaft in relation to the primary chain to advance and retard the timing.

The system improves low and high-speed engine performance, engine idle quality and exhaust emission.

The VVT system changes the phasing of the intake valves, relative to the fixed timing of the exhaust valves, to alter:

^ the mass of air flow into the engine's cylinders,
^ and the engine's torque response and emissions.

The VVT unit uses a vane device to control the camshaft angle (refer to VVT operation). The system operates over a range of 48' and is advanced or retarded to the optimum angle within this range.

The ECM. controls the VVT, using engine speed and load, engine oil temperature and throttle position signals to calculate the appropriate camshaft position.

The continuous VVT system provides the following advantages:

^ Reduces engine emissions and fuel consumption by further optimizing the camshaft timing, this improves the engine's internal exhaust gas re-circulation (EGR) effect over a wider operating range
^ Improves full-load torque characteristics as the camshaft timing is optimized at all engine speeds for superior volumetric efficiency
^ Improves fuel economy by optimizing torque over the engine's speed range.