TM 5-3805-260-24
PROCEDURE FOR MEASURING
CAMSHAFT LOBES
To find lobe lift (A) of camshaft, use the following
procedure:
1.
Measure lobe height (B) of one exhaust and one
intake lobe.
2.
Measure base circle (C) of one exhaust and one
intake lobe.
3.
Subtract base circle (C) dimension (STEP 2)
from lobe height (B) dimension (STEP 1). The
difference is actual lobe lift (A).
4.
The specified (new) lobe lift (A) is: -
(a) Exhaust lobe ......
.3071 in. (7.800 mm
(b) Intake lobe ........
.3077 in. (7.816 mm
5.
The maximum permissible difference
between actual lobe lift (STEIP 3) and specified lobe lif’t
(STEP 4) is .010 in. (0.25 mm).
LUBRICATION SYSTEM
One of the problems in the following list will generally
be an indication of a problem in the lubrication system for
the engine.
TOO MUCH OIL CONSUMPTION
OIL PRESSURE IS LOW
OIL PRESSURE IS HIGH
TOO MUCH COMPONENT WEAR
TOO MUCH OIL CONSUMPTION
Oil Leakage on Outside of Engine
Check for leakage at the seals at each end of the
crankshaft. Look for leakage at the oil pan gasket an all
lubrication system connections. Check to see if oil is
coming out of the crankcase breather. This can be
caused by combustion gas leakage around the pistons.
A dirty crankcase breather will cause high pressure is the
crankcase, and this will cause gasket and sea leakage.
Oil Leakage Into Combustion Area of Cylinders of
Cylinders
Oil leakage into the combustion area of the cylinders
can be the cause of blue smoke. There are three
possible ways for oil leakage into the combustion area of
the cylinders:
1.
Oil leakage between worn valve guides and
valve stems.
2.
Worn or damaged piston rings or dirty oil return
holes.
3.
Compression ring not installed correctly.
Too much oil consumption can also be the result of
using oil with the wrong viscosity. Oil with a thin (low
viscosity can be caused from dirt or fuel getting in the
crankcase, or by the engine getting too hot.
OIL PRESSURE IS LOW
An oil pressure gauge that has a defect may give an
indication of low oil pressure.
When the engine is running at rated speed with SAE
30 oil at operating temperature, the oil pressure
measured at the clean side of the oil filter at the oil filter
base will be 55 to 85 psi (380 to 590 kPa).
A minimum low pressure reading of 15 psi (105 Kpa)
is normal at low idle rpm. If there is no oil pressure, stop
the engine immediately. An 8M2744 Gauge, which is
part of 5P6225 Hydraulic Test Box, can be used for
checking pressure in the system.
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