GM 10224877 Engine Crankshaft

Do not overlook the bearings for use when a new crankshaft is being installed or when the crankshaft is being reground. First of all, install the rear main bearing oil seal on the top part of the cylinder block seat and on the bottom of the rear main bearing cap, the lips should facing the front of the engine; if the oil seal has two lips the helix should also face the front. For the seal halves use a protector installation tool and lubricate the seal lips with engine oil only. Subsequently, use the main bearings into the cylinder block and the main bearing caps and apply engine oil on the bearing surfaces. Take your time to ease the crankshaft into place in order not to mar the bearing surfaces. In order not to have the sealer obstruct the crankshaft or seal, paint a thin layer of brush on sealer selectively on the block mating surface and the corresponding surface of the bearing cap. Screw in the main bearing caps to the crankshaft and over the cylinder block so that arrow points to the front of the engine. All the attaching bolts of main bearing caps should be tightened to the indicated values but the rear bearing cap should tightened in the range of 10 to 12 ft.lbs initially. From the end of the crankshaft strike by the lead hammer both at the rear and at the front to center the rear bearing, and then re-tighten all bearing cap bolts as required. To determine crankshaft end play push the crankshaft as far forward as you possibly can and use a feeler gauge to determine the clearance between the front of the rear main bearing and the crankshaft thrust surface. Last, tighten the flywheel that will help in rotating the engine when reassembling.

Remove the bolts and lift off the main bearing caps, keeping them in order. Compare the width of the crushed Plastigage to determine the main bearing oil clearance, ensuring it meets specifications.

If a dial indicator is unavailable, feeler gauges can be used by prying the crankshaft to the front and measuring the clearance between the crankshaft and the thrust main bearing.

Finally, examine the main and rod bearing inserts.

If the crankshaft journals are damaged, tapered, out-of-round, or worn beyond specified limits, have the crankshaft reground by an automotive machine shop, ensuring the use of the correct size bearing inserts if reconditioned.

Gently tap the caps with a soft-faced hammer to separate them from the engine block, using the bolts as levers if necessary, and take care not to drop the bearing insert if it comes out with the cap.

Take the measurement at each end of the journal, near the crank throws, to determine if the journal is tapered.

To check the endplay of the crankshaft, mount a dial indicator with the stem in-line with the crankshaft and touching one of the crank throws. The crankshaft should be pushed all the way to the rear, and the dial indicator should be zeroed. Then, the crankshaft should be pried to the front as far as possible, and the reading on the dial indicator should be checked. The distance it moves is the endplay.

If the old bearing inserts are still in place, remove them from both the block and the main bearing caps.

Measure the connecting rod side-clearance with a feeler gauge between the connecting rod caps, and if the side clearance is outside the specified tolerance, replace the rod assembly.

Position the engine with the bottom facing up.

After unbolting the main bearing caps, each cap along with its corresponding bearing should be lifted off the crankshaft and placed on a workspace numbered to match their positions in the engine block.

Apply a thin, even layer of clean moly-base grease or engine assembly lube to the bearing surfaces in the block.

The bearing inserts should not be dropped if they come out with the caps.

Take the measurement at each end of the journal, near the crank throws, to determine if the journal is tapered.

Check the main and connecting rod bearing journals for uneven wear, scoring, pits, and cracks. Inspect the rest of the crankshaft for cracks and other damage, which should be magnafluxed by an automotive machine shop to reveal hidden issues.

For V6 engines, tighten the bolts starting from the center main and working outward, seating the thrust bearings before torquing the rear main cap.

Loosen the main bearing cap bolts a quarter turn at a time until they can be removed by hand, checking for markings on the caps to identify their locations, usually numbered from the front to the rear. If unmarked, use stamping dies or a center-punch to label them.

Check the main and connecting rod bearing journals for uneven wear, scoring, pits, and cracks. Inspect the rest of the crankshaft for cracks and other damage, which should be magnafluxed by an automotive machine shop to reveal hidden issues.

Most caps have a cast-in arrow indicating the front of the engine.

Loosen the main bearing cap bolts a quarter turn at a time until they can be removed by hand, checking for markings on the caps to identify their locations, usually numbered from the front to the rear. If unmarked, use stamping dies or a center-punch to label them.

Clean the bearing faces in the caps and install them in their respective positions with arrows pointing forward, tightening the main bearing cap bolts in three steps without rotating the crankshaft.

Remove the old bearing inserts and clean the main bearing surfaces with a lint-free cloth.

Examine the main and rod bearing inserts for further assessment.