GM 6.5L V8 – Cylinder Case and Crankshaft Passages

Oil leaving the filter travels through the cylinder case in several directions (refer to Figure 3-8). It flows to the #5 crankshaft main bearing and moves up a vertical passage at the rear of the cylinder case.

At the top of the vertical passage, oil flow moves to the oil pressure switch or gauge sending unit. During service, oil pressure is checked at the switch/sending unit fitting. Oil also travels to the left bank of hydraulic roller lifters, where it then travels to the camshaft bearings.

At camshaft bearing #5, oil travels in a circular passage around the bearing insert to a passage connected to the right bank of hydraulic roller lifters (see Figure 3-9). At the front end of this passage in the cylinder case, a fitting and special hose provide supply oil to the turbocharger. Due to the design of the turbocharger oil passages, engine operation does not require a cool-down idling procedure before shut-down to prevent coking.

At camshaft bearings #4, #3, #2 and #1, oil travels in circular passages around the bearing inserts to passages connected to the crankshaft main bearings.

During operation of the hydraulic roller lifters, some of the oil is squirted upward through the hollow push rods to the rocker arms. Some of the oil flow at the crankshaft #1 main bearing and camshaft #1 bearing splashes on the timing chain and sprockets, as well as the injection pump drive and driven gears.

Some of the lubricating oil flow at the crankshaft main bearings travels through passages connected with the crankpin journals (see Figure 3-10). During crankshaft rotation, some of the oil that exits from the sides of the connecting rod bearings is thrown upward to lubricate the piston pins and cool the undersides of the piston faces.

Once the oil from the pump reaches all its destinations, it drains back to the sump in the oil pan through open areas in the cylinder heads, cylinder case and front cover. The turbocharger has a special drain pipe/hose that connects to a metal flange on the lower right side of the cylinder case (see Figure 3-11).

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