The all aluminum engine block utilizes a deep skirt design for increased rigidity. The cylinders are
positioned in a straight in-line 6 cylinder orientation. The crankshaft bearing caps have a bearing beam or
"ladder" for enhaced structural rigidity and vibration reduction.
A single piece cast aluminum oil pan contributes to crankshaft and block rigidity while reducing overall
weight. The oil pan bolts to the bell housing as well as the block. This eliminates points of vibration and
makes the complete powertrain act as a single casting. Jack screws are used to remove the oil pan.
The crankshaft is a nodular iron design with seven main bearings.
The connecting rods are forged powdered metal. The connecting rods and caps are of a fractured split
design to improve durability and reduce internal friction. Care must be taken to ensure the mating
surfaces are not damaged during service procedures.
The pistons are a full-floating design. The piston pins are a slip fit in the bronze bushed connecting rod
and are retained in the piston by round wire retainers. There are two compression rings and one oil
The cylinder head is also made of the lost foam aluminum for lighter weight and rapid heat dissipation.
There are 4 valves per cylinder and the ports are of a high swirl design for improved combustion. The
cylinder head gasket consist of a steel laminated construction.
The engine utilizes dual overhead camshafts and roller followers for reduced friction, which results in
improved gas mileage.
A new electronic throttle control system is used on the engine. A throttle actuator control or TAC system
eliminates cable linkage from the pedal to the throttle control module. All throttle movements are controlled
by the PCM.
The oil pump is gear driven directly from the crankshaft. The oil pump drive gear is a slip fit to the
There is a front engine cover and a rear engine cover, both are made of aluminum. The front engine
cover and rear engine cover have "T" sealing joints and need to be removed after the oil pan. The front
and rear covers need to be installed before the oil pan. Jack screws are used to remove the covers.
Guide pins are used to aid in the installation of both covers.
4.2L Engine Mechanical Operation Description