TM 5-3825-226-24PROCEDURE FOR MEASURING CAMSHAFT LOBESTo find lobe lift (A) of camshaft, use thefollowing procedure:1.Measure lobe height (B) of one exhaust and oneintake lobe.2.Measure base circle (C) of one exhaust and oneintake lobe.3.Subtract base circle (C) dimension (STEP 2)from lobe height (B) dimension (STEP 1). Thedifference 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 betweenactual lobe lift (STEP 3) and specified lobe lift(STEP 4) is .010 in. (0.25 mm).CAMSHAFT LOBEA. Lobe lift. B. Lobe height. C. Base circle.LUBRICATION SYSTEMOne of the problems in the following list willgenerally be an indication of a problem in the lubricationsystem for the engine.TOO MUCH OIL CONSUMPTIONOIL PRESSURE IS LOWOIL PRESSURE IS HIGHTOO MUCH COMPONENT WEARTOO MUCH OIL CONSUMPTIONOil Leakage on Outside of EngineCheck for leakage at the seals at each end ofthe crankshaft. Look for leakage at the oil pan gasketand all lubrication system connections. Check to see ifoil is coming out of the crankcase breather. This can becaused by combustion gas leakage around the pistons.A dirty crankcase breather will cause high pressure inthe crankcase, and this will cause gasket and sealleakage.Oil Leakage Into Combustion Area of CylindersOil leakage into the combustion area of thecylinders can be the cause of blue smoke. There arethree possible ways for oil leakage into the combustionarea of the cylinders:1.Oil leakage between worn valve guides andvalve stems.2.Worn or damaged piston rings or dirty oil returnholes.3.Compression ring not installed correctly.Too much oil consumption can also be the resultof using oil with the wrong viscosity. Oil with a thin (low)viscosity can be caused from dirt or fuel getting in thecrankcase, or by the engine getting too hot.OIL PRESSURE IS LOWAn oil pressure gauge that has a defect maygive an indication of low oil pressure.When the engine is running at rated speed withSAE 30 oil at operating temperature, the oil pressuremeasured at the clean side of the oil filter at the oil filterbase will be 55 to 85 psi (380 to 590 kPa).A minimum low pressure reading of 15 psi (105kPa) is normal at low idle rpm. If there is no oilpressure, stop the engine immediately. An 8M2744Gauge, which is part of 5P6225 Hydraulic Test Box, canbe used for checking pressure in the system.2-67
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