17
N73B60 Engine - Diagnosis
Crankshaft
The N73 uses a forged steel
crankshaft (1 - front).
Each crankshaft throw has two
counterweights for balancing the
moving masses (12 counter-
weights in total).
The crankshaft is supported by
seven main bearings, the seventh
is the thrust bearing.
Crankshaft Thrust Bearing
The thrust bearing halves are multiple pieces that are assem-
bled as one part for the the number seven main bearing at the
rear of the engine.
Piston and Connecting Rod
The iron coated cast aluminum alloy pistons are “domed” with valve reliefs in the crowns
(1). The recess (2) directs the combustible mixture directly under the spark plug and pre-
vents the combustion chamber from being divided into two parts.
Piston rings:
• First piston ring groove = square ring
• Second piston ring groove = taperface ring
• Third piston ring groove = two-part oil control
ring
NNoottee::
Due to the shaping of the piston crown
and the wrist pin offset, the pistons are cylinder
bank specific (crown index arrow always points
to the front of the engine).
The forged steel connecting rod and cap is separated by the familiar “cracked” process.
The large end is angled at 30º allowing sufficient articulation in a very compact space. The
pistons are cooled by oil jets spraying under the exhaust side of the piston crown.
Crankshaft
KT-9635
KT-7676
KT-9634
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