Engine: Description and Operation

ENGINE CONSTRUCTION
Refer to images under Diagrams for exploded views of engine. Diagrams
Starting at the front of the engine, cylinders in the left bank are numbered 1-3-5 and cylinders in the right bank are numbered 2-4-6. The crankshaft is supported in the crankcase by four bearings.

The crankshaft is counterbalanced by the flywheel, crankshaft balancer, and weights cast into the crankshaft. Additional counterbalancing is obtained from the balance shaft which rides in the block above the camshaft and is driven by the camshaft.

All V-6 engines are even-firing, in that the cylinders fire at equal 120 degree intervals of crankshaft rotation. The location of the crankpins has been offset by 30 degrees in order to fire the cylinders at equal 120 degree intervals of crankshaft rotation.

The camshaft lobes and timing also reflect 120 degree spacing.

Thus, the even-firing crankshaft provides an equal interval of 120 degrees between ignition of each of the cylinders throughout the firing order.

The firing order is 1-6-5-4-3-2.

PISTONS
The aluminum alloy pistons have slipper skirts and are cam turned. Two transverse slots in the oil ring grooves extend through the piston wall and permit drain back of oil collected by the oil ring.

CAMSHAFT
The camshaft is supported in the crankcase by four steel-backed babbitt-lined bearings. It is driven from the crankshaft by sprockets and chain.

HEADS
The cylinder heads are cast iron and incorporate integral valve stem guides. Right and left cylinder heads are identical and interchangeable, although in service it is good practice to reinstall the cylinder heads on the side from which they are removed.

INTAKE MANIFOLD
The intake manifold is bolted to the inner faces of both cylinder heads so that it connects with all inlet ports.

Each exhaust and intake valve has a valve spring of ample capacity to insure positive seating throughout the operating speed range.

VALVE TRAIN
The valve rocker arms for.each hank of cylinders pivot on pedestals which bolt to the cylinder head.

Hydraulic roller valve lifters and tubular pushrods are used to operate overhead rocker arms and valves of both banks of cylinders from a single camshaft. This system requires no lash adjustment at time of assembly or in service. Operation of hydraulic valve lifters is described below.

In addition to its normal function of a cam follower, each hydraulic valve lifter also serves as an automatic adjuster which maintains zero lash in the valve train under all operating conditions. By eliminating all lash in the valve train and also providing a cushion of oil to absorb operating shocks, the hydraulic valve lifter promotes quiet valve operation. It also eliminates the need for periodic valve adjustment to compensate for wear of parts.

Oil is supplied to the lifter through a hole in the side of the lifter body which indexes with a groove and hole in the lifter plunger. Oil is then metered past the oil metering valve in the lifter, through the pushrods to the rocker arms.

When the lifter begins to move up the cam lobe, the check ball is held against its seat in the plunger by the check ball spring which traps the oil in the base of the lifter body below the plunger. The plunger and lifter body then raise as a unit, pushing up the pushrod to open the valve. The force of the valve spring which is exerted on the plunger through the rocker arm and pushrod causes a slight amount of leakage between the plunger and lifter body.

This allows a slow escape of trapped oil in the base of the lifter body. As the lifter rolls down the other side of the cam lobe and reaches the base circle or "valve closed" position, the plunger spring quickly moves the plunger back (up) to its original position. This movement causes the check ball to open against the ball spring and oil from within the plunger is drawn into the base of the lifter. This restores the lifter to zero lash.