The engine is a 6-cylinder in-line unit with an overhead valve mechanism (OHV), a cross-flow cylinder head made of aluminum alloy and a cast iron crankcase.
The crankshaft is installed in seven main bearings, the sixth of which is a thrust bearing, responsible for the amount of axial play of the shaft.
The pistons are equipped with upper and lower compression rings and a 3-section oil scraper ring.
The piston pins have a floating fit in the connecting rod heads and are tension-fitted into the pistons. The pins are secured with retaining rings.
The camshaft rotates in seven bearings and is equipped with a built-in distributor drive gear. The camshaft drive sprocket is mounted on its front end. The camshaft is driven from the crankshaft by means of a chain transmission (with roller chain). The rotation speed is half that of the crankshaft.
The second chain drives the oil pump from the crankshaft.
Lubrication of the timing gears and chains is carried out through a special nozzle installed in the front part of the cylinder block.
The valves are driven by solid pushrods, pushrods and cast rockers. The rockers are mounted on a common axle and lubricated through holes in its pedestals.
Replaceable valve guide bushings are pressed into the cylinder head and equipped with oil deflector caps that prevent the supply of excess oil compared to the required amount.
The rotary type oil pump is installed in the front part of the cylinder block. The cam located in the rear part of the oil pump drives the fuel pump. The oil pressure is maintained at a given level by means of a spring-loaded pressure reducing valve located inside the oil pump housing.
The engine crankcase is hermetically sealed with the clutch/rotation converter dome, which helps extend the life of the starter and clutch (on models with manual transmission). A plug is provided in the lower part of the clutch dome, which allows periodic drainage of moisture/oil accumulating in the crankcase.
[Data copied from web resource nissanbook.ru]