4.2L Vortec Straight Six Engine Description

Engine Block

The all aluminum engine block utilizes a deep skirt design that is important 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.

Cylinder Head

The cylinder head is also made of high quality aluminum for lighter weight and to help in rapid heat dissipation. There are 4 valves per cylinder and the ports are of a high swirl design for improved air and fuel combustion. The cylinder head gasket consist of a steel laminated construction with sealing rings.


The crankshaft is a basic nodular iron design with seven main bearings.

Oil Pan

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 to the block. This eliminates points of vibration and makes the complete powertrain act as a single casting unit. Jack screws are used to remove the oil pan. Alighnment pins are used for isntallation.

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Piston and Connecting Rod Assemblies

The pistons are a full-floating design. The piston pins are not pressed rigid but are a slip fit type in the bronze bushed connecting rod and are retained to the pistons by round wire retainers. There are two compression rings and one oil control ring as with most common engines. The connecting rods are forged powdered coated 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 removal or installation service procedures. Any damage or scoring means they would need to be replaced.

Fuel System

A new electronic throttle control system (TAC) is used on this 4.2L straight six cylinder 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 as requested by the pedal position sensor.

Valve Train

The engine utilizes dual overhead camshafts and roller followers for reduced friction which results in improved gas mileage and idle quality.

Engine Covers

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 is removed. 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.

Oil Pump

The oil pump is a rotary gear driven directly from the crankshaft. The oil pump drive gear is a slip fit to the crankshaft and provides high volume and consistant pressure.

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