Table of Contents
Advertisement
74
Maintenance Section
Overhaul (Top End)
• Chargecooler
• Camshafts
• Camshaft bearings
• Camshaft followers
• Connecting rods
• Crankshaft
• Gear train and bearings
• Governor
• Inlet air piping
• Oil cooler
• Pistons
• Ignition coils
• Valve train that includes the rocker gear
Overhaul (Top End)
Scheduling a Top End Overhaul
Top end overhauls can be scheduled between 12000
and 16000 hours depending on valve recession.
Record the valve depth at each service and then
calculate the valve recession. This measurement
provides an accurate indication of the rate of valve
wear. This measurement can be used to predict
when a cylinder head must be replaced.
Note: Generally, cylinder heads wear out at different
rates. Sometimes, servicing the cylinder heads at
different times may be the most economic decision.
The decision depends on the valve recession of the
individual cylinders. However, this decision must
include the costs of extra downtime that is caused by
this procedure. Perform an economic analysis to
determine if cylinder heads should be serviced as a
group or divided into smaller groups.
The generator or the driven equipment may also
require service when the engine overhaul is
performed.
Top End Overhaul Information
A top end overhaul involves servicing the cylinder
heads. During a top end overhaul, one piston should
be removed. Inspect the piston, piston rings, and the
cylinder liner. The condition of these components will
determine the period of the major overhaul.
Contact your Perkins distributor or Perkins dealer for
more information.
Monitoring Valve Seat Wear
At the required service interval, record the valve lash.
1. Remove the rocker covers.
2. Refer to Operation and Maintenance Manual,
"Engine Valve Lash and Bridge - Adjust".
3. On all engine cylinders, record the clearance
before any adjustments are made.
4. Set the valve bridges.
5. Adjust the valve lash to 0.4 mm (0.016 inch).
Note: After the engine valve lash is recorded,
Perkins recommends that the valve depth is
measured and recorded.
The valve depth is to be measured at every service.
The valve recession can then be calculated. The
values can be used to schedule a top end overhaul.
i09157681
Note: Perkins recommends that the valve depth is to
be measured before the installation of new cylinder
heads or during the commissioning of the engine to
obtain a baseline measurement.
The valve recession tool has been designed to give
service personnel a good indication of the cylinder
head valve recession or cylinder head valve seat
wear without the need to remove the cylinder heads.
For more information contact Perkins distributor.
Note: For earlier engines, the maximum permitted
inlet valve seat wear is 2.00 mm (0.07874 inch).
Note: For earlier engines, the maximum permitted
exhaust valve seat wear is 1.00 mm (0.040 inch).
Note: For later engines, the maximum permitted inlet
and exhaust valve seat wear is 3 mm (0.11811 inch).
Do not allow the recession of the valves to exceed
these limits.
Overhaul Considerations
Overhaul Information
An overhaul is replacing the major worn components
of the engine. An overhaul is a maintenance interval
that is planned. The engine is rebuilt with certain
rebuilt parts or new parts that replace the worn parts.
An overhaul also includes the following maintenance:
SEBU8430-02
i02896454
Advertisement
Table of Contents
