GMC S Series 1994, Руководство по ремонту

Страница: 321 / 919

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 crankshaft
main bearing journal.
VALVE TRAIN
A very simple ball pivot-type rocker arm is used.
Motion is transmitted from the camshaft through the
hydraulic roller lifter and pushrod to the rocker arm.
The rocker arm pivots on its ball and transmits the
camshaft motion to the valve.
The rocker arm ball is located on a stud threaded
into the head, and is retained by a nut. The pushrod is
located by a guide plate held under the rocker arm
stud, assuring that the rocker arm operates in the plane
of the valve.
INTAKE MANIFOLD
The intake manifold is cast aluminum.
EXHAUST MANIFOLD
The exhaust manifold is cast iron.
ENGINE LUBRICATION
Figure 5
Full pressure lubrication, through a full-flow oil
filter, is furnished by a gear type oil pump. Oil is
drawn up through the pick-up screen and tube and
passes through the pump to the oil filter.
The oil filter is a full flow paper element unit
with an anti-drain back valve. An oil filter by-pass is
used to ensure adequate oil supply, should the filter
become plugged or develop excessive pressure drop.
From the filter, oil is routed to the main oil
gallery which is rifle drilled above the camshaft to the
left of the camshaft centerline. This gallery supplies
hydraulic lifters with oil.
The hydraulic lifters pump oil up through the
pushrods to the rocker arms. Oil draining back from
the rocker arms is directed by cast dams, which are
part of the crankcase casting, to supply the camshaft
lobes with lubrication.
The passages supplying oil to the camshaft
bearings also supply the crankshaft main bearings
through intersecting vertical drilled holes. Oil from the
crankshaft main bearings is supplied to the connecting
rod bearings by means of intersecting passages drilled
in the crankshaft.
DISASSEMBLY OF ENGINE
TOOLS AND SHOP EQUIPMENT
A clean, well lit work area should be available.
Other necessary aides include: a suitable parts cleaning
tank, compressed air supply, trays to keep parts and
fasteners organized, and an adequate set of hand tools.
An approved engine repair stand will help
prevent personal injury or damage to the engine
components.
Special tools are illustrated throughout this
section, and listed at its end. These tools (or their
equivalents) are specially designed to quickly and
safely accomplish the operations for which they are
intended. The use of these tools will also minimize
possible damage to engine components.
Some precision measuring tools are required for
inspection of certain critical components. Torque
wrenches are necessary for the correct assembly of
various parts.
ACCESSORY REMOVAL
This section assumes that the engine accessories
have been removed. These accessories may include
one or more of the following:
• Power steering pump.
• Generator.
• A/C compressor.
It is beyond the scope of this section to detail the
many different accessory installations. Refer to the
appropriate
service manual section for this
information.
Diagrams of emission and vacuum hose routings,
wiring harness routings, accessory drive belt layout,
etc., should be made before removing accessories.
CLEANING
Remove the engine accessories before cleaning to
provide better access to engine exterior surfaces.
Cover the openings with tape to prevent the entry of
coolant, solvent and dirt.
Methods used to clean the engine will depend of
the equipment available. Steam cleaning, pressure
washing or solvent cleaning are some acceptable
methods. Allow the engine to dry before beginning the
work.
It is important that the engine be as clean as
possible to prevent dirt from entering critical areas
during disassembly.'
DRAINING THE ENGINE
[»->[ Remove or Disconnect
1. Oil pan drain bolt, and allow oil to drain from the
oil pan.
2. Oil filter.
3. Coolant drain plugs from block and allow to
drain.
Install or Connect
NOTICE:
Refer to “ Notice” on page 6A2-1.
1. Oil pan drain bolt.