TM 5-3895-346-14
ENGINE OVERHAUL
RUN-IN INSTRUCTIONS
E. FINAL RUN-IN
After all of the tests have been made and the Engine Test Report is completed through Section D, the engine is
ready for final test. This portion of the test and run-in procedure will assure the engine owner that his engine
has been rebuilt to deliver factory-rated performance at the same maximum speed and load which will be
experienced in the installation.
If the engine has been shutdown for one hour or longer, it will be necessary to have a warm-up period of 10
minutes at the same speed and load used for warm-up in the basic run-in. If piston rings, cylinder liners, or
bearings have been replaced as a result of findings in the basic run-in, the entire basic run-in must be repeated
as though the run-in and test procedure were started anew.
All readings observed during the final run-in should fall within the range specified in the Engine Operating
Conditions Specifications and should be taken at full load unless otherwise specified. Following is a brief
discussion of each condition to be observed.
The engine water temperature should be taken during the last portion of the basic run-in at full load. It should
be recorded and should be within the specified range.
The lubricating oil temperature reading must be taken while the engine is operating at full load and after it has
been operating long enough for the temperature to stabilize. This temperature should be recorded and should
be within the specified range.
The lubricating oil pressure should be recorded in psi or kPa after being taken at engine speeds indicated in the
Engine Operating Conditions Specifications.
The fuel oil pressure at the fuel manifold inlet passage should be recorded and should fall within the specified
range. Fuel pressure should be recorded at maximum engine speed during the final run-in.
Check the air box pressure while the engine is operating at maximum speed and load. This check may be
made by attaching a suitable gage (0-15 psi or 0-103 kPa) or manometer (15-0-15) to an air box drain or to a
handhole plate prepared for this purpose. If an air box drain is used as a source for this check, it must be
clean. The air box pressure should be recorded in inches of mercury.
Check the crankcase pressure while the engine is operating at maximum run-in speed. Attach a manometer,
calibrated to read in inches of water, to the oil level dipstick opening. Normally, crankcase pressure should
decrease during the run-in indicating that new rings are beginning to " eat-in".
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Check the air inlet restriction with a water manometer connected to a fitting in the air inlet ducting located 2
inches above the air inlet housing. When practicability prevents the insertion of a fitting at this point, the
manometer may be connected to a fitting installed in the 1/4 inch pipe-tapped hole in the engine air inlet
housing. If a hole is not provided, a stock housing should be drilled, tapped, and kept on hand for future use.
The restriction at this point should be checked at a specific engine speed. Then the air cleaner and ducting
should be removed from the air inlet housing and the engine again operated at the same speed while noting the
manometer reading. On turbocharged engines, take the reading on the inlet side of the turbocharger. The
difference between the two readings, with and without the air cleaner and ducting, is the actual restriction
caused by the air cleaner and ducting.
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