chevrolet truck Light Duty Truck 1994 Series Repair Manual Download

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GENERAL DESCRIPTION

ENG INE CO NSTRUCTIO N

The 4.3L engine, RPO LB4 (VIN Z), is a liquid-cooled

90-degree  V6  type  with  overhead  valves,  cast  iron
block,  and  cylinder  heads.  4.3L  (VIN  Z)  engines  used  in
C/K/S/T  vehicles  have  a  cast-iron  balance  shaft  mount
ed  in  the  crankcase  above  and  inline  with  the  camshaft.

For engine identification, refer to SECTION OA. For

engine com ponent identification refer to figures 1

through 6.

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  of  the  engine).  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-in  or  pressed-in  studs  (depending
on  where  the  engine  was  built).

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-hand 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

S/T Vehicles and C/K Vehicles with light duty

emissions

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 MANIFOLD

A cast-iron intake m anifold is used that has an

exhaust gas recirculation (EGR) port cast into it for the
mixture of exhaust gases with the fuel and air mixture.

ENGINE LUBRICATION

Lubrication schematics are shown in figures 7 through

10. The gear type oil pump is driven from the distributor

shaft, which is gear driven from the camshaft. Oil is
drawn into the oil pump through a pickup screen and
pipe.

Pressurized oil is routed to the oil filter. In case of

excessive oil pressure, a bypass valve is provided. Fil

tered  oil  flows  into  the  main  gallery  and  then  to  the
camshaft,  balance  shaft  rear  bearing  (S/T vehicles),  and
crankshaft  bearings.  The  valve  lifter  oil  gallery  supplies

chevrolet truck Light Duty Truck 1994 Series, Repair Manual

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