GMC S Series 1994, Repair Manual

Page: 451 / 919

The crankshaft is supported by five precision insert
type bearings, with crankshaft thrust taken at the num­
ber five (rear) bearing.
The connecting rods are forged steel, with precision
insert type crankpin bearings. The piston pins are a
press fit in the connecting rods.
The pistons are cast aluminum alloy. The piston pins
are a floating fit in the pistons.
The gear-type oil pump is driven through an exten­
sion shaft from the distributor driveshaft which is gear
driven from the camshaft. The oil is drawn from the
engine oil pan through a pickup screen and tube. Pres­
surized oil is delivered through internal passages to the
cam shaft and crankshaft to lubricate the bearings.
Lubrication diagrams are shown in figures 1, 2, and 3.
ENGINE IDENTIFICATION
Two basic types of engines, with three different dis­
placements, are covered in this section.
The first type is the “ small block” engine, which is
available in 5.0L (305 CID) and 5.7L (350 CID) dis­
placements.
The second type is the 7.4L (454 CID) engine, which
is sometimes referred to as the “ Mark” engine.
To determine the displacement of the engine, use the
vehicle identification number (VIN) of the vehicle the
engine was removed from. Refer to “ Specifications” at
the end of this section. If the VIN is not available, the
bore and stroke of the engine involved can be mea­
sured and compared against “ Specifications” to deter­
mine the engine model; or, with “ Mark” engines, the
engine displacement (in liters) is cast into each side of
the cylinder block.
Refer to Section 0A in this manual for further engine
identification information. Refer to figures 4 through 11
for engine component identification.