GM 14020567 PIISTON

In most cases of high mileage engines, original pistons need replacement due to the requirement of boring the cylinders to a larger size for normal wear compensation; however, if the cylinder walls only need slight finish honing, old pistons may be reused if they are in good condition. Clean connecting rods and pistons using a cleaning solvent and dry them with compressed air if available, avoiding wire brushes or abrasive tools on any piston part. Use a groove cleaner tool to clean the ring grooves of the piston, ensuring that oil ring holes and slots are also clean. Inspect the rods for twisting, bending, nicks, or cracks, as any issues found necessitate replacement with new rods. Check the piston for cracked ring lands, skirts, or pin bosses, and look for worn or wavy ring lands, scuffed or damaged skirts, and eroded areas at the top; any damaged pistons or those showing excessive wear should be replaced. Examine the ring grooves for nicks that could cause the rings to hang up. While the piston is still connected to the connecting rod, swivel the rod back and forth to assess the degree of difficulty, comparing all piston/rod assemblies; if the rods appear loose on the piston pins and move with little or no drag, the piston pins are worn and need replacement. If the cylinder block requires any machine work, including finish honing, the machinist will likely want the pistons available to check piston-to-bore clearance as the cylinder walls are cut, making this measurement critical and best left to the machine shop.