TM 5-3895-346-14
RUN-IN INSTRUCTIONS
ENGINE OVERHAUL
ENGINE RUN-IN INSTRUCTIONS
Following a complete overhaul or any major repair job involving the installation of piston rings, pistons, cylinder
liners, or bearings, the engine should be run-in on a dynamometer prior to release for service.
The dynamometer is a device for applying specific loads to an engine. It permits the serviceman to physically
and visually inspect and check the engine while it is operating. It is an excellent method of detecting improper
tuneup, misfiring injectors, low compression, and other malfunctions, and may save an engine from damage at
a later date.
The operating temperature within the engine affects the operating clearances between the various moving parts
of the engine and determines to a degree how the parts will wear. Normal coolant temperature (160-185 or
F
71-85 ) should be maintained throughout the run-in.
C
The rate of water circulation through the engine on a dynamometer should be sufficient to avoid having the
engine outlet water temperature more than 10 or 6 higher than the water inlet temperature. Though a 10
F
C
F
or 6 rise across an engine is recommended, it has been found that a 15 or 8 temperature rise maximum
C
F
C
can be permitted.
Thermostats are used in the engine to control the coolant flow. Therefore, be sure they are in place and fully
operative or the engine will overheat during the run-in. However, if the dynamometer has a water standpipe
with a temperature control regulator, such
BASIC ENGINE RUN-IN SCHEDULE
ENGINE BRAKE HORSEPOWER
4-Valve Cylinder Head
Time Minutes
Speed RPM
Injector Size
4-53
NA
10
600
All
0
10
1500
All
20
5A50
5A55
10
Rated
5A60
Speed
N-65
5N65*
5A50
5A55
10
Rated
5A60
Speed
N-65
5N65*
120
2000
All
30
2200
All
87
120
2200
All
30
2800
All
115
Power
Rated
All
Final BHP to be within
Check
Speed
5% of rated
After run-in DO NOT run continuous full load during first 10 hours or 500 miles.
" "BHP indicates running at no-load for specified time and speed.
O
390
