The cast iron balance shaft is mounted in the
crankcase above and in-line with the camshaft. A
camshaft gear drives the gear attached to the
balance shaft. The front end of the balance shaft is
supported by a ball-type bearing. The rear end of
the balance shaft uses a sleeve-type bearing.
The steel camshaft is supported by four bearings
pressed into the engine block. The camshaft timing
chain sprocket mounted to the front of the
camshaft is driven by the crankshaft sprocket
through a camshaft timing chain.
The cast nodular iron crankshaft is supported by
four crankshaft bearings. The number four
crankshaft bearing at the rear of the engine is the
end thrust bearing. The crankshaft bearings are
retained by bearing caps that are machined with
the engine block for proper alignment and
clearances. The crankshaft position sensor reluctor
ring has three lugs used for crankshaft timing and
is constructed of powdered metal. The crankshaft
position sensor reluctor ring has a slight
interference fit onto the crankshaft and an internal
keyway for correct positioning.
The cast iron cylinder heads have one intake and
one exhaust valve for each cylinder. A spark plug is
located between the valves in the side of the
cylinder head. The valve guides and seats are
integral to the cylinder head. The 4.3L heavy duty
applications have pressed in exhaust valve seats.
The valve rocker arms are positioned on the valve
rocker arm supports and retained by a bolt.
The cast iron engine block has six cylinders
arranged in a V shape with three cylinders in each
bank. Starting at the front side of the engine block,
the cylinders in the left bank are numbered 1-3-5
and cylinders in the right bank are numbered 2-4-6
(when viewed from the rear). The firing order of the
cylinders is 1-6-5-4-3-2. The cylinders are encircled
by coolant jackets.
The cast iron exhaust manifolds direct exhaust
gases from the combustion chambers to the
exhaust system. The left side exhaust manifold has
a port for the EGR valve inlet pipe.
Chevy 4.3L Vortec Engine Mechanical Description
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
lower manifold has an exhaust gas recirculation (EGR) port cast
into the manifold for mixture. The (EGR) valve bolts into the lower
intake manifold. The Central Sequential Multiport Fuel Injection
system uses multiple fuel injectors to meter and distribute fuel to
each engine cylinder. The Central (SFI) 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 (SFI) unit. The delivery
tubes independently distribute fuel to each cylinder through
nozzles 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. The connecting rods are forged steel. The
connecting rods are machined with the rod cap installed for proper
clearances and alignments.
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.
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