Engine: Description and Operation

DESCRIPTION
The 4.6L (281 CID) engine is an 8 cylinder "V" gasoline engine. It is of the overhead cam design and operates on unleaded fuel. This is NOT a free-wheeling engine, it is an interference type engine. If it has jumped time, there will be damage to the valves and pistons (6108) and will require the removal of the cylinder heads.

AIR/FUEL SYSTEM
The fuel/air mixture needed for burning in the cylinders is provided by sequential multiport fuel injection (SFI). This fuel induction system is mounted on an aluminum intake manifold which in turn is bolted to aluminum cylinder heads. Refer to Powertrain Management for information on the SFI system and air induction components.

CAMSHAFT
The dual overhead camshafts are housed in the cylinder heads. The four camshafts are individually chain-driven with a hydraulic timing chain tensioner (6L266) on each timing chain. The are limited in end play and thrust loads by the No.1 cylinder head camshaft journal caps.

CYLINDER HEAD
The cylinder heads are aluminum and house the dual overhead camshafts. There are four valves per cylinder

CYLINDER BLOCK
The cylinder block is:
^ 90° V.
^ cast aluminum.

INTAKE MANIFOLD
A two piece aluminum intake manifold (9424) is bolted to the aluminum cylinder heads.

OIL PUMP
The gerotor oil pump is mounted on the front face of the cylinder block. The inner rotor is piloted on the crankshaft post and is driven through flats on the crankshaft.

POSITIVE CRANKCASE VENTILATION (PCV)
This engine incorporates a closed-type positive crankcase ventilation (PCV) system and exhaust emission control system. All engine/emission control systems are covered in Powertrain Management. To maintain the required exhaust emission levels, the fuel system, ignition system, and engine must be kept in good operating condition and meet recommended adjustment specifications.

SERVICING
When performing tests, adjustments or service to the engine, ignition system or fuel system, it is essential to follow the proper procedures and specifications. Refer to the proper component or system. Refer to Powertrain Management for emission control or computer control information. Make sure that the following engine components are not serviceable before replacing damaged or worn engine components:
^ crankshaft.
^ cylinder heads.
^ valve guides.
^ exhaust valves.
^ intake valve.
^ camshafts.
^ cylinder block.

VALVE TRAIN
The valve train operates as follows:
^ Hydraulic ball tip hydraulic lash adjusters (6500) provide automatic lash adjustment.
^ Roller followers ride on the camshaft lobes, transferring the camshafts up and down motion to the valves in the cylinder heads (6049).