Points for piston assembly during engine overhaul

In the operation of engine overhaul, the assembly quality of each component directly affects the performance of the engine after repair, and the assembly of the piston set is the most important one. If the assembly is improper, it may cause serious consequences such as component damage. The assembly points of the piston set will be described below.

Assembly of pistons and connecting rods

Assembly operation: Apply engine oil to the piston pin, piston pin seat hole, and connecting rod small head bushing. Put the connecting rod small head into the piston and align the pin hole with the piston pin. Pass the piston pin through the connecting rod small head hole. Pass and install it in place, and install limit springs at both ends of the piston pin seat hole.

Assembly points: There will be direction marks on the connecting rod and piston, usually bumps or arrows. These marks should generally face the timing system. That is, the markings on the top of the connecting rod and piston should be on the same side. Be careful not to install them incorrectly .

Installation of piston rings

Assembly operation: Generally there are 3 piston rings, 2 air rings and 1 oil ring from top to bottom. Each ring has a direction mark, such as the letter "TOP", and the side with the direction mark faces the top of the piston.

Assembly points: The staggered position of the piston ring is the key factor that determines the sealing effect of the piston ring. The opening of the first air ring should face the side of the cylinder wall with less pressure on the receiving side, which can reduce wear. If it is an integral oil ring, the openings of the three piston rings should be staggered 120 ° from each other; if the oil ring is composed of two oil scrapers, the two air rings are staggered 180 º, and the two oil rings of the combined oil ring The blades are staggered 180 º, and the upper wiper blades of the second air ring and the combined oil ring are staggered 90 º.

Assembly of the piston into the cylinder

Assembly operation: Taking a 4-cylinder engine as an example, the order of assembling the piston rod into the cylinder is 1-cylinder, 4-cylinder, 2-cylinder, and 3-cylinder. Rotate the crankshaft so that the connecting rod journals of cylinders 1 and 4 are at the lowest point. Put a special tool on the outer circle of the piston ring to compress the piston ring to be flush with the outer circle of the piston. 

Assembly points: When the piston connecting rod is installed in the cylinder, the correct orientation needs to be selected according to the marks on the piston and the connecting rod. During the process of pushing into the piston, the big end of the connecting rod should always face the connecting rod journal on the crankshaft to avoid misalignment or damage to the connecting rod bolts.