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Bearing Lubrication
Every bearing receives lubrication through holes drilled into the crankshaft. Main bearings receive oil first from the oil pump and the main oil gallery. The oil enters the main bearing journal and drilled passages connecting to the rod bearing journals Figure 87. Most main bearing journals are cross-drilled through the journal centerline so that the oil hole aligns with a single annular groove in the top bearing shell twice for every crankshaft revolution. Without the annular groove, oil supply is otherwise cut off, so many main bearings have an annular groove down the center of both halves of the main bearing that allows oil to flow around the main bearing journal. An oil clearance around the bearing is calculated by subtracting the diameter of the bearing bore from the shaft diameter.
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FIGURE 08-87: Lubrication oil travels from the main bearing journals to the rod journals through cross-drilled oil passageways in the crankshaft.
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