Chevrolet Silverado / GMC Sierra. Service manual — part 218

The intake manifold is a two-piece design. The upper portion is made from a composite material
and the lower portion is cast aluminum. The throttle body attaches to the upper manifold. The
Central Multipoint Flexible Injection system uses multiple fuel injectors to meter and distribute
fuel to each engine cylinder. The Central (MFI) is retained by a bracket bolted to the lower
intake manifold. The fuel meter body also houses the pressure regulator. Metal inlet and outlet
fuel lines and nylon delivery tubes connect to the Central (MFI) unit. The delivery tubes
independently distribute fuel to each cylinder through injectors located at the port entrance of
each manifold runner where the fuel is atomized.

Piston and Connecting Rod Assemblies

The cast aluminum pistons use two compression rings and one oil control assembly. The piston is
a low friction, lightweight design with a flat top and barrel shaped skirt. The piston pins are offset
0.9 mm (0.0354 in) toward the major thrust side, right side, to reduce piston slap as the
connecting rod travels from one side of the piston to the other side after a stroke. The piston pins
have a floating fit in the piston and are retained by a press fit in the connecting rod. Powdered
metal connecting rods were introduced into production in late 2006. Powdered metal connecting
rods and rod bearing caps are NOT interchangeable. They must be assembled with the mating
surfaces properly oriented and aligned, and the piston, piston pin, and connecting rod are to be
serviced as an assembly.

Valve Train

Motion is transmitted from the camshaft through the hydraulic roller valve lifters and the tubular
valve pushrods to the roller type valve rocker arms. The roller type valve rocker arm pivots on a
needle type bearing in order to open the valve. The valve rocker arms for each bank of cylinders
are mounted to a one piece valve rocker arm support. Each valve rocker arm is retained on the
valve rocker arm support and the cylinder head by a bolt. The hydraulic valve lifters keep all the
parts of the valve train in constant contact. Each hydraulic valve lifter acts as an automatic
adjuster and maintains zero lash in the valve train. This eliminates the need for periodic valve
adjustment.

NEW PRODUCT INFORMATION

The purpose of New Product Information is to highlight or indicate important product changes
from the previous model year.

Changes may include one or more of the following items:

A component comparison from the previous year

Fastener changes

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

Torque values and/or fastener tightening strategies

Changed engine specifications

New sealants and/or adhesives

Disassembly and assembly procedure revisions

Engine mechanical diagnostic procedure revisions

New special tools required

Component Comparison

Powdered metal connecting rods have replaced forged connecting rods.

Torque Values and/or Fastener Tightening Strategies

Addition of powdered metal connecting rod torque specification.

Changed Engine Specifications

No changes for 2007.

New Sealants and/or Adhesives

No new sealants or adhesives for 2007.

Disassembly and Assembly Procedure Revisions

Instructions added specific to powdered metal connecting rod service.

Engine Mechanical Diagnostic Procedure Revisions

No changes for 2007.

New Special Tools Required

No changes for 2007.

LUBRICATION DESCRIPTION

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

Fig. 731: Engine Lubrication
Courtesy of GENERAL MOTORS CORP.

Full pressure lubrication, through a full-flow oil filter is supplied by a gear-type oil pump. Oil is
drawn up through the oil pump screen and passes through the pump to the oil filter. The oil filter
is a full-flow paper element unit with an anti-drain back valve. An oil filter bypass valve is used
to ensure adequate oil supply, in the event the filter becomes plugged or develops excessive
pressure drop. Filtered oil flows into the main gallery and then to the camshaft, the balance shaft,
the rear bearing, and the crankshaft bearings. The valve lifter oil gallery supplies oil to the valve
lifters. Oil flows from the valve lifters through the hollow valve pushrods to the valve rocker

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

arms. Oil drains back to the crankcase through the oil drain holes in the cylinder head. The
camshaft timing chain is drip fed from the front camshaft bearing. The pistons and piston pins are
lubricated by oil splash.

CLEANLINESS AND CARE

Throughout this section, it should be understood that proper cleaning and protection of
machined surfaces and friction areas is part of the repair procedure. This is considered
standard shop practice even if not specifically stated.

When any internal engine parts are serviced, care and cleanliness is important.

When components are removed for service, the components should be marked, organized or
retained in a specific order for re-assembly.

At the time of installation, the components should be installed in the same location and with
the same mating surface as when removed.

An automobile engine is a combination of many machined, honed, polished and lapped
surfaces with tolerances that are measured in millimeters or thousandths of an inch. The
surfaces should be protected to avoid component damage.

Apply a liberal amount of clean engine oil to friction areas during assembly.

Proper lubrication will protect and lubricate friction areas during initial operation.

SEPARATING PARTS

Mark or identify the following components:

Piston and the piston pin

Piston to the specific cylinder bore

Piston rings to the specific cylinder bore

Connecting rod to the crankshaft journal

Connecting rod to connecting rod cap

Crankshaft bearings and connecting rod bearings

Engine camshaft and valve lifters

IMPORTANT: Many internal engine components will develop specific wear

patterns on their friction surfaces.
When disassembling the engine, internal components MUST be
separated, marked and organized in a way to ensure
reinstallation to original location and position.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado