SECTION LLubricating SystemThe importance of correct and clean lubricationcannot be stressed too highly and all references toengine oil should be taken to mean lubricating oil whichfalls within the specification given in the appendix. Careshould be taken that the oil chosen is that specified forthe climatic conditions under which the engine isoperated.The sump should be filled with a suitable grade oflubricant to the correct level but do not overfill above thefull mark.DescriptionThe lubrication is of the forced feed type, the oilbeing circulated, under pressure, by a lobed rotor typeoil pump which is mounted on the front main bearing capand driven through an idler gear by the crankshaft gear.The oil is drawn through a sump strainer and a suctionpipe before entering the pump itself. Oil is then pumpedvia a pipe to the relief valve housing and then through aninternal drilling in the cylinder block to an externallymounted adaptor onto which is fitted the full flow typelubricating oil filter. This adaptor channels the oil first toand from the oil cooler section of the heat exchanger, bymeans of flexible pipes, then through this full flowlubricating oil filter back into the cylinder block. The oilpasses via drillings within the cylinder block to thepressure rail (main oil gallery).With lowline engines, the oil cooler and lubricatingoil filter are an integral component fitted on the starboardside of the engine.From the pressure rail the oil is fed through oilwaysin the crankcase webs to the five main bearings andthen from these through oilways drilled in the crankshaftwebs the oil passes to the big ends. An oil seal preventsoil leaking along the crankshaft at the rear end and oilthrown from this seal returns to the sump.The three camshaft bearings are lubricated throughoilways in the crankcase webs from numbers one, threeand five main bearings.The camshaft centre bearing supplies a controlledfeed of oil through an oilway, in the cylinder block andcylinder head, to the rocker shaft assembly. Thiscontrolled feed is achieved by allowing oil underpressure to be forced to the rocker shaft only when theoilways in the camshaft journal and camshaft centrebearing are in line, this occurring once per camshaftrevolution. Oil from the rocker shaft escapes through asmall bleed hole in each rocker lever and lubricates thevalves and guides by splash, the surplus oil beingreturned to the sump by gravity.The idler gear and hub are pressure lubricated directfrom the pressure rail. Oil enters the rear of the hub andpasses through drillings in the hub to lubricate the idlergear bush and gear retaining plate. Timing gear teethare splash lubricated by surplus oil from the frontcamshaft bearing idler gear hub and fuel pump hub.Pistons, cylinder liners and connecting rod small endbearings are lubricated by splash and oil mist, also thecams and tappets of the valve mechanism.THE OIL PUMPThe oil pump is secured to the front main bearingcap by three setscrews, a protrusion of the idler gearshaft locating in a hole in the bearing cap to give positivelocation.The bushed idler gear which is free to rotate on itsshaft transmits the drive from the crankshaft gear to theoil pump gear.The oil pump drive gear is pressed and keyed on tothe pump driven shaft on the other end of which ispressed and pinned a three lobed rotor. This rotormeshes with a four lobed driven rotor, which is free torotate in the cast iron pump body.
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