Chevrolet 1980 Light Duty Truck Service Manual page 489

General Description................................................. 6A5-1
Engine Lubrication.................................................. 6A5-4
On Vehicle Service.................................................... 6A5-6
Engine Mounts........................................................ 6A5-6
Intake Manifold...................................................... 6A5-6
Exhaust Manifold.................................................... 6A5-10
Rocker Arm Cover................................................ 6A5-10
Valve Mechanism.................................................... 6A5-11
Valve Stem Oil Seal and/or
Valve Spring.............................................................. 6A5-11
Valve Lifters............................................................ 6A5-12
Cylinder Head Assembly....................................... 6A5-13
Rocker Arm Studs.................................................. 6A5-16
Valve Guide Bores.................................................. 6A5-16
Valve Seats.............................................................. 6A5-16
Valves....................................................................... 6A5-16
Torsional Damper................................................... 6A5-17
GENERAL DESCRIPTION (FIG. 6A5-1 & 6A5-2)
CYLINDER BLOCK
The cylinder block is made of cast iron and has 8
cylinders arranged in a "V" shape with 4 cylinders in each
bank. Five main bearings support the crankshaft which is
retained by bearing caps that are machined with the block
for proper alignment and clearnances. Cylinders are
completely encircled by coolant jackets.
CYLINDER HEAD
The cast iron cylinder heads have individual intake and
exhaust ports for each cylinder. Valve guides are integral,
and rocker arms are retained on individual threaded studs.
CRANKSHAFT AND BEARINGS
The crankshaft is cast nodular iron, and is supported
by five main bearings. Number five bearing is the end thrust
bearing.
All main bearings are lubricated from oil holes that
connect to the main oil gallery. This runs along the left side
of the cylinder case, just above the oil pan rail. Two
additional galleries supply oil to the valve lifters.
A torsional damper on the forward end of the
crankshaft dampens any engine torsional vibrations.
CAM SH A FT AND DRIVE
The cast iron camshaft is supported by five bearings
and is chain driven. A steel crankshaft gear drives the timing
chain which in turn drives the camshaft through an
aluminum and nylon sprocket.
SECTION 6A5
7.4 L (W) V-8 - RPO LE8
Contents
Crankcase Front Cover......................................... 6A5-17
Oil Seal (Front Cover)........................................... 6A5-18
Camshaft................................................................. 6A5-18
Camshaft Bearings.................................................. 6A5-19
Oil P an ..................................................................... 6A5-20
Oil Pump.................................................................
Connecting Rod Bearings...................................... 6A5-21
Main Bearings......................................................... 6A5-22
Oil Seal (Rear M ain).............................................
Connecting Rod Piston Asemblies.................... 6A5-25
Cylinder Block ....................................................... 6A5-28
Oil Filter ByPass Valve......................................... 6A5-29
Engine Assembly..................................................... 6A5-29
Crankshaft...............................................................
Sprocket or Gear Replacement............................. 6A 5-30
Specifications.............................................................
Cam lobes are ground, hardened and tapered with the
high side toward the rear. This, coupled with a spherical
face on the lifter, causes the valve lifters to rotate.
Camshaft bearings are lubricated through oil holes
which intersect the main oil gallery. The main oil gallery
is rifle drilled down the left side of the cylinder case.
PISTONS AND CONNECTING RODS
The pistons are made of cast aluminum alloy using two
compression rings and one oil control ring. Pins are
Chromium steel and have a floating fit in the pistons They
are retained in the connecting rods by a press fit.
Connecting rods are made of forged steel. Full pressure
lubrication is directed to the connecting rods by drilled oil
passages from the adjacent main bearing journal. Oil holes
at the connecting rod journals are located so that oil is
supplied to give maximum lubrication just prior to full
bearing load.
VALVE TRAIN
A very simple ball pivot-type train is used. Motion is
transmitted from the camshaft through the hydraulic lifter
and push rod to the rocker arm. The rocker arm pivots on
its ball and transmits the camshaft motion to the valve. The
rocker-arm ball is retained by a nut.
M A R K IV 6A5-1
6A5-21
6A5-24
6A5-30
6A5-31
LIG H T T R U C K SER V ICE M ANUAL