REMOVAL & INSTALLATION
See Figures 1, 2, 3 and 4
This procedure requires the removal of the engine from the vehicle and placement on an engine stand. It cannot be done with the motor in the car.
- Follow the procedures under piston and connecting rod removal in this section.
- Remove the pressure plate and clutch disc or, if automatic transmission, the flexplate. Loosen the bolts diagonally, a few turns at a time, to prevent warping. It will be necessary to lock the flywheel (or flexplate) in position while loosening its retaining bolts. Matchmark the flywheel and crankshaft before disassembly so that the parts may be reconnected in the same relationship.
- Remove the rear sealing flange and the front cover plate from the block.
- Check the main bearing caps for identification numbers and, if necessary, number them.
- Unbolt and remove the main bearing caps and lift the crankshaft out of the block. You are reminded that the crankshaft is a heavy component.
Do not interchange bearing shells and caps.
- Remove the bearings from the main caps and the block.
Installation is the reverse of the removal procedures taking note of the following:
- Make sure that matched bearing pairs are installed together.
- The holes in the bearing shells must coincide with the oilways in the engine block.
- Check the bearing clearances with Plastigage.
- Lubricate the bearing shells and bearing surfaces on the crankshaft.
- Tighten the main bearing caps to specification and check the crankshaft end play.
CRANKSHAFT CLEANING AND INSPECTION
See Figures 5, 6 and 7
- Clean the oilways in the crankshaft with a piece of wire and blow them out with compressed air. Also check and clean the sealing surfaces on the crankshaft.
- Measure out-of roundness and taper of crank pins (journals). Use a micrometer and take measurements at several different positions. Maximum out-of-round is 0.0003 in. (0.008mm) and the maximum taper is 0.0004 in. (0.01mm). Crank pins can be ground to a smaller size. Regrinding should be perfomed by a competent machine shop.
- If a warped crankshaft is suspected, it should be checked with a dial indicator. Support the crankshaft by the two outer main bearing journals on V-blocks. Rotate the crankshaft one turn and measure the out-of-true for the two center crankpins. Maximum warpage is 0.02mm (0.0008 in.).
CHECKING BEARING CLEARANCE
See Figures 8 and 9
Invert the engine on its stand and remove the cap from the bearing to be checked. Using a clean dry rag, thoroughly clean all oil from crankshaft journal and bearing insert.
Plastigage® is soluble in oil; any oil on the journal or bearing could result in erroneous readings.
Place a piece of Plastigage® along the full length of journal, reinstall cap, and tighten to the specifications given in the chart earlier in this section.
Remove bearing cap, and determine bearing clearance by comparing the width of Plastigage® to the scale on Plastigage® envelope. Journal taper is determined by comparing width of the Plastigage® strip near its ends. Rotate crankshaft 90° and retest, to determine journal eccentricity.
Do not rotate crankshaft with Plastigage® installed.
If bearing insert and journal appear intact and are within tolerances, no further main bearing service is required. If bearing or journal appear defective, cause of failure should be determined and repaired before replacement and reassembly.