GM 25198520 Piston,Engine

Before the piston and connecting rod assemblies can be taken out, the cylinder head and oil pan have to be first detached. You should also run your fingernail across the top end of ring travel; any ridge that is formed must be trimmed by the use of a reamer since failure to do so is likely to cause a breakage of the piston. Then, retract all the ridges then rotate the engine in such a manner that the crankshaft will be at the uppermost position. Measure the amount of end play of connecting rod with the help of feeler gauges and check that the amount should lie within the boundary line: if there is cross then new connecting rods are required. It is possible to mark some of the connecting rods and caps for identification and then loosen the connecting rod cap bolts together with the cap itself, being extremely careful not to drop the bearing insert. Withdraw the connecting rod and piston assembly through the top of the engine if necessary using a wooden dowel for piston expulsion and do the same for the remaining cylinders. Once removed screw back the caps and inserts in order to avoid further damage during examination. If you are going to put new piston rings, ensure that the ring end gaps are correct and also the side clearance of the piston ring. Place the pistons with the rings in the cylinder block beginning by the oil control ring then the second and third ring. At final assembly, the cylinder walls should be clean, the edges of the cylinder should be chamfered and the crankshaft should be fitted. Do not lubricate the bearing inserts during the cleaning and replacement process as well as alignment of the piston ring gaps, and additionally for the lubrication of the piston and rings use only a piston ring compressor for the installation. Verify the oil clearance of the connecting rod bearing using Plastigage obtaining the right size and condition of the bearing inserts. Once the clearance is confirmed apply the grease to the bearing faces; fit the rod cap with new bolts and tighten to the desired torque figure. The same must be done for all the assemblies, always cleaning them and checking their orientation during the entire course of the activity. Last but not the least, turn the crankshaft and look for binding and at the same time inspect and adjust for connecting rod endplay.