Engine: Description and Operation

CYLINDER BLOCK AND BEDPLATE ASSEMBLY
A partial open deck is used for cooling and weight reduction with water pump molded into the block.
Nominal wall thickness is 4 mm. The bedplate incorporates main bearing caps. Rear seal retainer is integral with the block.

CRANKSHAFT
A nodular cast iron crankshaft is used. The engine has 5 main bearings, with number 3 flanged to control thrust. The 52 mm diameter main and 48 mm diameter crank pin journals (all) have undercut fillet radiuses that are deep rolled for added strength. To optimize bearing loading 8 counterweights are used. Hydrodynamic seals provide end sealing, where the crankshaft exits the block. Anaerobic gasket material is used for parting line sealing. A sintered iron timing belt sprocket is mounted on the crankshaft nose. This sprocket provides motive power; via timing belt to the camshaft sprocket providing timed valve actuation.

PISTONS
The DOHC Engine DOES NOT have provision for a freewheeling valve train. Non freewheeling valve train means, in the event of a broken timing belt, pistons will contact the valves. All engines use pressed-in piston pins to attach forged powdered metal connecting rods. The connecting rods are a cracked cap design and are not repairable. Hex head cap screw are used to provide alignment and durability in the assembly.

PISTON RINGS
The piston rings include a molybdenum faced top ring for reliable compression sealing and a taper faced intermediate ring for additional cylinder pressure control. Oil Control Ring Package contains of 2 steel rails and an expander spacer.

CYLINDER HEAD
Features a Dual Over Head Camshaft (DOHC), 4 valves per cylinder, cross flow design. The valves are arranged in two in-line banks, with the ports of the bank of two intake valves per cylinder facing toward the radiator side of engine and ports of the bank of two exhaust valves per cylinder facing toward the dash panel. Cylinder head incorporates powder metal valve guides and seats. Integral oil galleries within the cylinder head supplies oil to the hydraulic lash adjusters, camshaft and valve mechanisms.

CAMSHAFTS
The nodular iron camshafts have six bearing journals and 2 cam lobes per cylinder. Flanges at the rear journals control camshaft end play. Provision for cam position sensor is located on the intake camshaft at the rear of cylinder head. A hydrodynamic oil seal is used for oil control at the front of the camshaft.

VALVES
Four valves per cylinder are actuated by roller cam followers which pivot on stationary hydraulic lash adjusters. All valves have 6 mm diameter chrome plated valve stems. The valve sizes are 34.8 mm (1.370 inch) diameter intake valves and 30.5 mm (1.20 inch) diameter exhaust valves. Viton rubber valve stem seals are integral with the spring seats. Valve springs, spring retainers, and locks are conventional.

INTAKE MANIFOLD
The intake manifold is a two piece aluminum casting, attached to the cylinder head with ten fasteners. This long branch fan design enhances low and midspeed torque.

EXHAUST MANIFOLD
The exhaust manifold is made of nodular cast iron for strength and high temperatures. Exhaust gasses exit through a machined, articulated joint connection to the exhaust pipe.

COMPONENT REPLACEMENT
If any of the following parts have been changed or replaced:
^ Camshaft
^ Camshaft Position Sensor
^ Camshaft Position Sensor Target Magnet
^ Cylinder Block
^ Cylinder Head
^ Water Pump
^ Powertrain Control Module (PCM)
^ Timing Belt and Timing Belt Tensioner
The camshaft and crankshaft timing relearn procedure must be performed. Refer to the component Removal and Installation procedure.