Mandrel A.60308 is a cylindrical rod with a diameter and length of the working part, respectively, 21 and 80 mm. The diameter of the centering shank that fits into the piston pin bore is (14,9±0,05) mm.
If some parts of the connecting rod and piston group are not damaged and slightly worn, then they can be reused. Therefore, when disassembling, they mark them in order to later assemble a group with the same parts and install them in the same engine cylinder.
Before assembly, pick up a finger to the piston. For proper mating, it is necessary that the piston pin, lubricated with engine oil, enter the piston bore by simply pressing the thumb and not fall out of it if you hold the piston with the piston pin in a vertical position. The drop-down finger is replaced by another, of the following category (see sect. «Device Features»). If the piston had a third category pin, then replace the piston with a piston pin.
Since the pin is inserted into the top end of the connecting rod with an interference fit, it is necessary to heat the connecting rod to expand the top end. To do this, the connecting rods are placed for 15 minutes in an electric furnace heated to 240°C. For better heating, the connecting rods are placed with their upper heads inside the furnace.
The finger is prepared in advance for assembly by putting it on roller 1 (pic. 44) fixture A.60325 and installing between the finger and the handle a distance ring 4 mm thick, with an outer diameter of 22 mm and an inner diameter of 15 mm. A guide 2 is installed at the end of the device and fixed with a screw 3. The screw is loosely tightened so that jamming does not occur when the finger expands from contact with the heated connecting rod.
To properly connect the pin to the connecting rod, press-fitting must be carried out as soon as possible, since the connecting rod cools quickly and after cooling it will not be possible to change the position of the pin. The piston with connecting rod must be assembled so that the arrow on the piston crown points towards the outlet of the oil hole on the bottom head of the connecting rod (see fig. 5).
The connecting rod removed from the furnace is quickly clamped in a vice. Put the piston on the connecting rod, making sure that the hole for the pin coincides with the hole in the upper head of the connecting rod. The piston pin fixed on the fixture is pushed into the piston bore and into the upper head of the connecting rod (pic. 45) until the stop of the shoulder of the tool in the piston. During this operation, the piston must be pressed by the boss against the upper head of the connecting rod in the direction of pressing the pin (shown by the arrow in Fig. 45). Then the finger will take the correct position.
After cooling the connecting rod, lubricate the finger with engine oil through the holes in the piston bosses. Lubricate the grooves on the piston and piston rings with engine oil and install the rings on the piston. Orient the piston rings so that the top compression ring lock is approximately 45°to the piston pin axis, the lower compression ring lock is approximately 180°to the top compression ring lock axis, and the small ring lock is approximately 90°to the piston pin axis. top compression ring.
The lower compression ring is installed with the groove down. If the ring is marked «Top» or «TOR», then the ring is set with the mark up (to the bottom of the piston). Before installing the oil scraper ring, it is checked that the joint of the spring expander is located on the side opposite to the ring lock.