Chevrolet 1980 Light Duty Truck Service Manual page 419

General Description................................................. 6A1-1
Engine Lubrication.................................................. 6A1-2
On Vehicle Service................................................... 6A1-9
Engine Mounts........................................................ 6A1-9
Manifold Assembly-Non-Integrated Head.......... 6A1-10
Exhaust Manifold-Integrated Head...................... 6A1-10
Rocker Arm Cover................................................ 6A1-11
Push Rod Side Cover............................................ 6A 1-11
Valve Mechanism................................................... 6A1-11
Valve Stem Oil Seal and/or Valve Spring........... 6A1-11
Valve Lifters............................................................ 6A1-13
Cylinder Head......................................................... 6A1-14
Rocker Arm Studs................................................. 6A1-15
Valve Guides........................................................... 6A1-15
Valve Seats.............................................................. 6A1-16
C Y LIN D ER BLO C K
The cylinder block is made of cast iron and has 6
cylinders arranged "In-Line". Seven main bearings support
the crankshaft which is retained by recessed bearing caps
that are machined with the block for proper alignment and
clearances. Cylinders are completely encircled by coolant
jackets.
C Y LIN D ER HEAD
The cast iron cylinder head has individual intake and
exhaust ports for each cylinder. Valve guides are integral
and rocker arms are retained on individual threaded studs
pressed into head. The 4.1 L(D) heads have integrated inlet
manifolds. The 4.8 L(T) uses separate inlet manifolds.
C R A N K SH A FT AND B EA R IN G S
The crankshaft is cast nodular iron and is supported
by seven main bearings. Number seven bearing is the end
thrust bearing. Main bearings are lubricated from oil holes
which intersect the main oil gallery located on the right side
of the block. The cam bearings are also fed oil by
intersecting holes with main oil gallery. The lifters are
located in the main oil gallery.
A damper assembly, on the forward end of the
crankshaft, dampens any engine torsional vibrations. The
outer ring of the damper is grooved for the accessory drive
belts.
Section 6A1
Contents
4.1 L (D) L-6 - RPO LE3
L (T) L-6 - RPO L25
GENERAL DESCRIPTION
Valves....................................................................... 6A1-16
Torsional Damper................................................... 6A1-16
Crankcase Front Cover......................................... 6A 1 -16
Oil Seal (Front Cover)........................................... 6A1-17
Camshaft................................................................. 6A1-17
Camshaft Bearings................................................. 6A1-18
Oil P an .................................................................... 6A1-19
Oil Pump................................................................. 6A1-19
Engine Bearings...................................................... 6A1-20
Oil Seal (Rear M ain)............................................. 6A1-23
Piston and Connecting Rod Assemblies.............. 6A1-24
Flywheel.................................................................. 6A1-28
Engine Assembly..................................................... 6A1-29
Crankshaft............................................................... 6A1-30
Specifications............................................................. 6A1-31
C A M S H A FT AND D RIVE
The cast iron camshaft is supported by four bearings
and is gear driven. A cast iron crankshaft gear drives the
aluminum camshaft gear. Cam lobes are ground, hardened
and tapered with the high side toward the rear. This,
coupled with a spherical face on the lifters, causes the valve
lifters to rotate.
P ISTO N S AND CO N N ECTIN G RODS
The pistons are made of a cast aluminum alloy using
two compression rings and one oil control ring.
Piston pins in the 4.1 L (D ) engine are offset .060"
(1.5mm) toward the thrust side (right hand side) to provide
a gradual change in thrust pressure against the cylinder wall
as the piston travels its path. This also provides for quieter
operation. 4.8 L (T) engine piston pins are on piston
centerline for best durability and reduced friction. 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.
IN-LINE 6 6A1-1
LIG H T T R U C K S ER V ICE M ANUAL