TM 5-3825-226-24
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 (STEP 3) and specified lobe lift
(STEP 4) is .010 in. (0.25 mm).
CAMSHAFT LOBE
A. Lobe lift. B. Lobe height. C. Base circle.
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
and 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 in
the crankcase, and this will cause gasket and seal
leakage.
Oil Leakage Into Combustion Area 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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