Chevrolet Silverado / GMC Sierra. Service manual — part 412

A single piece cast aluminum upper oil pan contributes to crankshaft and block rigidity while
reducing overall weight.

Crankshaft

The crankshaft is a nitride hardened steel design with five main bearings. Crankshaft thrust is
controlled by the number 5 bearing.

Connecting Rods

The connecting rods are one-piece hot forged steel. The connecting rods and caps are of a
fractured split design to improve durability and reduce internal friction. The connecting rod small
end is tapered cut for reduced weight and improved durability.

Pistons

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. The pistons have a piston
cooling oil channel cast inside of the piston. These cooling oil channels utilize an oil jet located at
the bottom of the cylinder bore to direct oil into the piston channel. There are two compression
rings and one oil control ring. There is a groove machined into the pistons between the first and
second compression rings. This groove reduces compression ring leakage by providing an empty
space for expanding gases, reducing the combustion gas pressure on the second compression ring.

Cylinder Heads

The cylinder heads are made of 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 gaskets consist of an all steel laminated construction.

Valve Train

The engine utilizes a mechanical roller lifter for valve operation. The shaft mounted rocker arms
have roller tips for reduced friction and wear. One rocker arm operates two valves simultaneously
through a valve bridge.

Fuel System

The fuel system is of a direct injection fuel rail design. A high pressure pump mounted within the
valley is gear driven directly from the camshaft. This pump provides a continuous and constant
high pressure fuel supply to the fuel rails. The electronically controlled fuel injectors receive their
fuel supply from these fuel rails. The fuel injection control utilizes a pilot injection method to
reduce the combustion noise that is common in traditional diesel engines. The pilot injection

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

method reduces noise by supplying a small amount of fuel to the cylinder just before the normal
combustion timing.

Turbocharger

The turbocharger is water cooled for improved durability.

Oil Cooler

The oil cooler lowers engine temperature by cooling the oil with engine coolant. Engine coolant
is directed from the water pump to the oil cooler by a coolant tube. The oil filter attaches directly
to the oil cooler.

Oil Pump

The oil pump is gear driven directly from the crankshaft. The oil pump drive gear is a slip fit to
the crankshaft.

Water Pump

The water pump is gear driven for improved reliability.

Engine Covers

There is a front engine cover and a flywheel housing, both are made of aluminum. The full bell
flywheel housing is cross bolted to the upper oil pan. The flywheel housing also supplies a
crossover passage for engine coolant. The front engine cover houses the gear train and provides a
mounting surface for the cooling fan pulley assembly.

LUBRICATION DESCRIPTION

Lubrication Flow Schematic

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Fig. 48: Lubrication Flow Schematic
Courtesy of GENERAL MOTORS CORP.

Engine lubrication is supplied by a gear type oil pump assembly. The pump is mounted on the
front of the engine block and driven by the oil pump drive gear on the crankshaft. The pump gears
rotate and draw oil from the oil pan sump through a pick-up screen and pipe. The oil is
pressurized as it passes through the pump and is sent through the engine block oil galleries.
Contained within the oil pump assembly is a safety relief valve that eliminates overpressurization.
Pressurized oil is directed through the sub oil gallery (5) to the full flow oil filter where harmful
contaminants are removed. Two bypass valves are incorporated into the oil cooler assembly
which will permit oil flow in the event the filter or the oil cooler become restricted.

The oil is directed to the main oil gallery (4), and from the main oil gallery it flows to the piston
cooling channel left bank (3), and the sub oil gallery (6) on the right bank. The sub oil gallery on
the right bank supplies oil to the right bank piston cooling channel (1). Located in the front cover
at the sub oil gallery (6) is an oil pressure relief valve which regulates oil pressure within
operating range.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Oil flows from the main gallery (4) to the vertical crankshaft/camshaft bearing galleries (2). From
the crankshaft/camshaft bearing galleries (2), the oil flows to both the camshaft bearings and the
crankshaft main bearings. Oil flows from the crankshaft main bearings to the connecting rod big
end.

Oil flows from the crankshaft/camshaft bearing galleries (2) to the number 1 camshaft bearing
(7), where it splash lubricates the fuel injection pump gear.

Oil flows from the crankshaft/camshaft bearing galleries (2) to the number 2 and 5 camshaft
bearings (8).

Oil flows from the crankshaft/camshaft bearing galleries (2) to the number 3 camshaft bearing
(9), where it exits to both cylinder heads and enters the hollow rocker arm shafts. Oil flows
through the rocker arm shafts and rocker arms where it lubricates the upper valve train
components.

On production LB7 engines through 2004, oil flowed through the rocker arms, through the
passage in the valve adjusting screw, and into the hollow pushrods where it was directed to the
valve lifters. Beginning with the 2004.5 engine (LLY), lifters with hardened rollers were used
and did not require hollow pushrods for additional oil flow. However, hollow pushrods were
used in production until approximately the start of the 2006 model year, after which the hole in
the push rod ends was removed. The hollow pushrods can be used for any model year, whereas
the pushrods without the holes in the ends can only be used for 2004.5 model year and newer
production engines.

Oil flows from the crankshaft/camshaft bearing galleries (2) to the number 4 camshaft (10), where
it exits into the turbocharger oil supply line to lubricate the turbocharger. Oil exiting the
turbocharger is routed through the turbocharger oil return pipe and into the flywheel housing.

CLEANLINESS AND CARE

An automobile engine is a combination of many of the following surfaces:

Machined

Honed

Polished

Lapped

The tolerances of these surfaces are measured in the ten-thousandths of an inch. When you service
any internal engine part, cleanliness and care are important. Apply a liberal coating of engine oil

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado