GMC 12514101 Piston Kit,(W/Pinion & Rings)(Std)

Prior to removing the piston and connecting rod assemblies, position the engine upright. Use a ridge reamer to completely eliminate the ridge at the top of each cylinder, following the manufacturer's instructions, as failure to do so may result in piston breakage. Once all cylinder wear ridges are removed, turn the engine upside-down. Before removing the connecting rods, check the endplay by mounting a dial indicator aligned with the crankshaft and touching the side of the number one cylinder connecting rod cap. Push the connecting rod forward to zero the dial indicator, then push it to the rear and note the reading; if the endplay exceeds the service limit, a new connecting rod is necessary. Alternatively, feeler gauges can be used to measure the endplay by inserting them between the connecting rod and crankshaft throw until the play is eliminated. Check for identification marks on the connecting rods and caps, and if absent, use a small punch to mark them. Loosen each connecting rod cap nut about half a turn, remove the number one connecting rod cap and bearing insert without dropping the insert, and protect the crankshaft journal and cylinder wall by slipping a short length of plastic or rubber hose over each connecting rod cap bolt before pushing the connecting rod/piston assembly out through the top of the engine with a wooden tool. If resistance is encountered, ensure all ridge material has been removed. Repeat this process for the remaining cylinders, and after removal, reassemble the connecting rod caps and bearing inserts in their respective rods, installing the cap nuts finger tight to prevent accidental damage to the bearing surfaces.

Each piston should be carefully inspected for cracks, scoring, scuffing, holes, and burned areas, as these can indicate overheating, abnormal combustion, or spark knock.

After clearing the cylinder ridges, turn the engine upside-down with the crankshaft facing up.

Check the connecting rod bearing oil clearance before permanently bolting the rod cap in place.

Remove the rod cap carefully to avoid disturbing the Plastigage, then compare the width of the crushed Plastigage to the scale on the container to obtain the oil clearance, ensuring it meets specifications.

Take them to a machine shop for inspection of bend and twist, and avoid disassembly unless necessary.

By scraping and using a hand-held wire brush or fine emery cloth. It is important not to use an electric drill with a wire brush as it can erode the soft piston material.

A ridge reamer should be used, following the manufacturer's instructions.

Finally, rotate the crankshaft by hand to check for any obvious binding.

Before removing the connecting rods, check the endplay with feeler gauges by sliding them between the first connecting rod and the crankshaft throw until the play is removed. The endplay is equal to the thickness of the feeler gauge(s).

The cylinder bores should be perfectly clean, which can be achieved by wiping the cylinder walls several times with light engine oil and a clean, lint-free cloth.

Before installing the piston rings, measure the ring end gap for each ring by arranging them into sets that include a rap ring, a 2nd ring, and a three-piece oil control ring.

Remove the nuts on the connecting rod stud in sequence and lift the cap off the crankshaft.

If the cylinder block requires any machine work, including finish honing, it is advisable to have the pistons available for checking piston-to-bore clearance, which is a critical measurement best left to the machine shop.

If the endplay exceeds the service limit, new connecting rods will be required.

Piston ring side clearance, piston-to-bore clearance, and piston-to-rod clearance should be measured to ensure proper matching.

Repeat this process for all remaining pistons/connecting rods.

If the pistons are undamaged and the engine block is not rebored, new pistons may not be necessary, although new piston rings should always be used during a rebuild.

Carefully tap the top of the piston with a wooden hammer handle while guiding the connecting rod into place on the crankshaft journal, maintaining downward pressure on the ring compressor to prevent the piston rings from popping out.

Position the engine upright.

Clean the back side of the other bearing insert and install it in the rod cap, again ensuring the tab fits into the recess without applying lubricant.

Check the connecting rod bearing oil clearance by laying a piece of Plastigage on the number one connecting rod journal.

Temporarily remove rod caps to inspect connecting rods for cracks and damage, checking bearing surfaces for nicks and scratches. Then replace old bearings and secure the caps.

With the notch on top of the piston facing the front of the engine, gently place the piston and connecting rod assembly into the number one cylinder bore, resting the bottom edge of the ring compressor on the engine block, and tap the top edge to ensure contact.

A piston ring groove-cleaning tool should be used to remove carbon deposits from the ring grooves. Alternatively, a piece of broken old ring can be used, taking care not to remove any metal or damage the grooves.

Turn the engine upside-down.

If pistons need to be removed from the connecting rods for new installations or if the piston pins have excessive play, take them to an automotive machine shop for inspection of bend and twist.

Position the engine upright.