GMC S Series 1994 Repair Manual Download

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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

GMC S Series 1994, Repair Manual

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