chevrolet truck Light Duty Truck 1994 Series, Руководство по ремонту

Страница: 409 / 919

GENERAL DESCRIPTION
ENGINE CONSTRUCTION
The 4.3L engine, RPO L35 (VIN W), is a liquid-cooled
90 degree V6 type with overhead valves, a balance
shaft, and cast iron block and cylinder heads.
For engine identification, refer to SECTION 0A. For
engine com ponent identification refer to figures 1
through 4.
CYLINDER BLOCK
The cylinder block has 6 cylinders arranged in a “ V”
shape with 3 cylinders in each bank. Starting at the
front of the engine, cylinders in the right bank are num­
bered 1-3-5 and cylinders in the left bank are numbered
2-4-6 (when viewed from the front). The firing order of
the cylinders is 1-6-5-4-3-2. The cylinders are encircled
by coolant jackets.
CYLINDER HEADS
The 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 are integral and the rocker arms are retained on
individual threaded studs.
CRANKSHAFT
The crankshaft is supported by four main bearing
inserts. The number four bearing at the rear of the
engine is the end thrust bearing. The bearings are
retained by bearing caps that are machined with the
block for proper alignment and clearances.
CAMSHAFT
The camshaft is supported by four full round, sleeve
type bearings. A sprocket on the crankshaft drives a
timing chain which in turn drives the camshaft through a
sprocket.
PISTONS AND CONNECTING RODS
The pistons are made of cast aluminum alloy using
two compression rings and one oil control ring. Piston
pins are offset 1.6 mm (1/16 inch) 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 pins are a press fit in the
connecting rod and a floating fit in the piston.
BALANCE SHAFT
The cast iron balance shaft is mounted in the crank­
case 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
bearing and the opposite end uses a sleeve bearing.
VALVE TRAIN
The valve train is a ball pivot type. Motion is transmit­
ted from the camshaft through the hydraulic lifter and
pushrod to the rocker arm. The rocker arm pivots on its
ball and transmits the camshaft motion to the valve.
The hydraulic valve lifters with roller followers keep all
parts of the valve train in constant contact. Each lifter
acts as an automatic adjuster and maintains zero lash
in the valve train and eliminates the need for periodic
valve adjustment.
INTAKE MANIFOLDS
The two-piece intake manifold assembly consists of
upper and lower cast aluminum manifolds. The throttle
body is integral with the upper manifold. The lower
manifold has an exhaust gas recirculation (EGR) port
cast into it for the mixture of exhaust gases with the fuel
and air mixture.
The intake manifolds also house the central port
injection (CPI) system. This system uses a single injec­
tor to meter and distribute fuel to all the engine cylin­
ders. The injector is housed in a fuel meter body. The
fuel meter body also houses the pressure regulator.
Nylon inlet and outlet fuel lines and nylon delivery tubes
connect to the CPI system. The delivery tubes indepen­
dently distribute fuel to each cylinder through nozzles
located at the port entrance of each manifold runner
where the fuel is atomized.