GMC 12646457 Piston Kit

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Prior to removing the piston/connecting rod assemblies, check for ridges formed at the upper limit of ring travel and remove them if necessary. Turn the engine so the crankshaft is facing up. Check the connecting rod endplay with feeler gauges and consult an automotive machine shop if necessary. Mark the connecting rods and caps for identification. Remove the connecting rod cap bolts and the number one connecting rod cap and bearing insert. Push the connecting rod/piston assembly out through the top of the engine. Repeat this procedure for the remaining cylinders. Reassemble the connecting rod caps and bearing inserts and install the cap bolts finger tight. Check the piston ring end gaps and adjust if necessary. Install the rings on the pistons, starting with the oil control ring. Check that the upper and lower side rails can rotate smoothly. Install the number two and number one rings. Repeat this procedure for the remaining pistons and rings. Clean the cylinder walls, chamfer the top edge of each cylinder bore, and ensure the crankshaft is in place. Clean the bearing surfaces of the connecting rod and cap. Lubricate the piston and rings and use a piston ring compressor to compress the rings. Rotate the crankshaft and apply oil to the cylinder walls. Insert the piston/connecting rod assembly into the cylinder bore. Check the connecting rod bearing oil clearance using Plastigage. Clean the bearing faces and apply grease or engine assembly lube. Slide the connecting rod back into place, install the rod cap, and tighten the bolts. Repeat this procedure for the remaining pistons/connecting rods. Rotate the crankshaft to check for any binding and check the connecting rod endplay.

12646457 PISTON KIT, ENG