The oil pumps primary purpose is to circulate engine oil under pressure to the bearings, pistons and the camshaft. This lubricates these systems, allows the use of higher-capacity fluid bearings and also assists in engine cooling.
This is a main big end for the Isuzu FVM and FTR model truck. A big end is the end of a connecting rod that engages with a crankshaft. The top end of the connecting rod is called the small end, and the bottom end is called the big end. He crawled under the engine every 15 miles or so to examine the big end for overheating.