Replacing the crankshaft is usually part of an engine overhaul job. However, unlike many other components you can simply remove from around the engine block, removing, handling and installing the crankshaft requires a special procedure. Since you are replacing or reconditioning the crankshaft, plan on installing a new set of bearings as well. With the engine out of the vehicle and the rest of the components off the block, you are ready to work on the crankshaft.
Mount the engine block on an engine stand for support or set it on a workbench.
Inspect the main bearing caps. They should be numbered consecutively, starting at the front of the engine. Arrows on the caps should point to the front of the engine as well. If necessary, use a stamping die set to identify each cap so you can replace them in their exact location and position.
Rotate alternately each bearing cap bolt a 1/4-turn counterclockwise starting at the centre of the block and working toward the front and rear until you can remove the bolts by hand. Use a breaker bar and a short socket, and keep the bolts organised so you can replace them in their original location during the reassembling process.
Remove the main bearing caps from the block. If necessary, gently tap each cap with the wooden handle of a hammer to dislodge them from the block. Keep each main bearing attached to the inside of the caps when you remove them.
Lift the crankshaft off the engine block with an assistant's help and set the crankshaft in a safe place standing in an upright position. This will prevent the crankshaft weights from weighing down on the unit's centre line.
Replace the bearing caps in their original location on the engine block and install the bolts finger-tight in their respective place.
Take the engine block and crankshaft to a machine shop for cleaning, inspection and, if necessary, reconditioning. Ask them to check for crankshaft end play and provide you with the correct bearings' size. And remember to store the crankshaft in an upright position until you are ready to reassemble it.
Mount the engine block on the engine stand or set it on a workbench.
Install the new bearings on the engine block with the small bearing tab seating properly on the recess provided on the block saddle. Make sure the small oil hole in each bearing aligns with the oil hole in its respective saddle. Remember that the centre bearing is built with flanges on each side to control end play.
Coat with a thin layer of moly-base grease the faces of the new main bearings you installed on the engine. Coat the crankshaft journals as well. The journals are the area on the crankshaft where the bearings will be resting on.
Lay the crankshaft carefully on the engine block with the help of an assistant.
Install the other half of the new bearings on the main bearing caps. Also, align the bearing tabs with the recess provided on the cap saddle and coat the bearing faces with a thin layer of moly-base grease.
Install the bearing caps in their correct places on the engine block. Make sure the numbers on the caps run consecutively from the front to the rear of the engine and the arrows on the caps point to the front of the engine.
Install the bearing-caps mounting bolts finger-tight. Tighten the bolts snugly using the breaker bar and short socket. Finally, torque the bolts alternately in three steps starting at the centre and working your way to the front and rear of the engine. Use a torque wrench and short socket. Consult your particular vehicle service manual for the correct torque to apply to the main bearing caps. Or you may ask the technician in your machine shop for this number.
Tap the crankshaft ends forward and backward 10 times with a brass hammer and retorque the main bearing caps with the torque wrench and short socket.
Install the crankshaft pulley bolt at the front of the crankshaft finger-tight and rotate the crankshaft several times to check for binding. Use the breaker bar and a socket.