- Drain the engine oil and remove the engine from the car. Mount the engine on a work stand in a suitable working area. Invert the engine, so the oil pan is facing up.
- Remove the engine front (timing) cover.
- Remove the timing chain/belt and gears/pulleys.
- Remove the oil pan.
- Remove the oil pump.
- Stamp the cylinder number on the machined surfaces of the bolt bosses of the connecting rods and caps for identification when reinstalling. If the pistons are to be removed eventually from the connecting rod, mark the cylinder number on the pistons with silver paint or felt-tip pen for proper cylinder identification and cap-to-rod location.
- Remove the connecting rod caps. Install lengths of rubber hose on each of the connecting rod bolts, to protect the crank journals when the crank is removed.
- Mark the main bearing caps with a punch (preferably a number punch) so that they can be reinstalled in their original positions.
- Remove all main bearing caps.
- Note the position of the keyway in the crankshaft so it can be installed in the same position.
To keep the connecting rods from banging against the side of the cylinders while removing the crankshaft, screw four oil pan bolts loosely into the block, then stretch a rubber band between a connecting rod bolt and an oil pan bolt for each of the pistons
- Carefully lift the crankshaft out of the block. The rods will pivot to the center of the engine when the crank is removed.
MAIN BEARING INSPECTION
Like connecting rod big-end bearings, the crankshaft main bearings are shell-type inserts that do not utilize shims and cannot be adjusted. The bearings are available in various standard and oversizes; if main bearing clearance is found to be too sloppy, a new bearing (both upper and lower halves) is required.
Generally, the lower half of the bearing shell (except No. 1 bearing) shows greater wear and fatigue. If the lower half only shows the effects of normal wear (no heavy scoring or discoloration), it can usually be assumed that the upper half is also in good shape. Conversely, if the lower half is heavily worn or damaged, both halves should be replaced. Never replace one bearing half without replacing the other.
See Figures 1 and 2
Main bearing clearance can be checked both with the engine in the car and with the engine out of the car. If the engine block is still in the car, the crankshaft should be supported both front and rear (by the damper in front and flywheel at the rear in order to remove clearance from the upper bearing). Total clearance can then be measured between the lower bearing and journal. If the block has been removed from the car, and is inverted, the crank will rest on the upper bearings (taking up clearance) and the total clearance can be measured between the lower bearing and journal. Clearance is checked in the same manner as the connecting rod bearings, with Plastigage® or an equivalent gauging material.
Crankshaft bearing caps and bearing shells should NEVER be filed flush with the cap-to-block mating surface to adjust for wear in the old bearings. Always install new bearings
- If the crankshaft has been removed, install it (block removed from car). If the block is still in the car, remove the oil pan and oil pump, then be sure the crankshaft is supported to remove upper clearance. Starting with the rear bearing cap and working on one cap at a time, moving towards the front, remove the cap and wipe all oil from the crank journal and bearing.
- Place a strip of Plastigage® the full width of the bearing, (parallel to the crankshaft), on the journal.
- Install the bearing cap and evenly torque the cap bolts to specification.
- Remove the bearing cap. The flattened Plastigage® will stick to either the bearing or the crankshaft journal.
- Use the graduated scale on the Plastigage® envelope to measure the material at its widest point.
If the flattened Plastigage® tapers toward the middle or ends, there is a difference in clearance indicating the bearing or journal has a taper, low spot, or other irregularity. If this is indicated, measure the crank journal with a micrometer
- If bearing clearance is within specifications and no scoring or damage is visible, the bearing insert is in good shape. Replace the insert if the clearance is not within specifications. Always replace both upper and lower inserts as a unit.
- Standard, 0.001 in. (0.025mm) or 0.002 in. (0.051mm) undersize bearings should produce the proper clearance. If these sizes still produce too sloppy a fit, the crankshaft must be reground for use with the next undersize bearing. Recheck all clearances after installing new bearings.
- Replace the rest of the bearings in the same manner. After all bearings have been checked, rotate the crankshaft to make sure there is no excessive drag.
MAIN BEARING REPLACEMENT
Engine Out of Car
- Remove and inspect the crankshaft.
- Remove the main bearings from the bearing saddles in the cylinder block and main bearing caps.
- Coat the bearing surfaces of the new, correct size main bearings with clean engine oil and install them in the bearing saddles in the block and in the main bearing caps.
- Install the crankshaft. For details, please refer to crankshaft Installation.
See Figures 3 through 7
- With the oil pan, oil pump or pickup and spark plugs removed, remove the cap from the main bearing needing replacement and remove the bearing from the cap.
- Make a bearing roll-out pin, (using a bent cotter pin) as shown in the illustration. Insert the end of the pin in the oil hole in the crankshaft journal.
- Rotate the crankshaft clockwise as viewed from the front of the engine. This will roll the upper bearing out of the block.
- Lube the new upper bearing with clean engine oil and insert the plain (un-notched) end between the crankshaft and the indented or notched side of the block. Roll the bearing into place, making sure that the oil holes are aligned. Remove the roll pin from the oil pin.
- Lube the new lower bearing and install the main bearing cap. Making sure it is positioned in the proper direction with the matchmarks in alignment.
- Torque the main bearing cap bolts to the proper specification.
Please refer to crankshaft installation for thrust bearing alignment
CRANKSHAFT END-PLAY AND INSTALLATION
See Figures 8 through 13
When main bearing clearance has been checked, bearings examined and/or replaced, the crankshaft can be installed. Thoroughly clean the upper and lower bearing surfaces, and lube them with clean engine oil. Install the crankshaft and main bearing caps.
Dip all main bearing cap bolts in clean oil, and torque all main bearing caps, excluding the thrust bearing cap, to specifications (please refer to the charts located in this section to determine specifications and which bearing is the thrust bearing). Finger-tighten the thrust bearing bolts. To align the thrust bearing, pry the crankshaft the extent of its axial travel several times, holding the last movement toward the front of the engine. Add thrust washers, if required for proper alignment. Torque the thrust bearing cap to specifications.
To check crankshaft end-play, pry the crankshaft to the extreme rear of its axial travel, then to the extreme front of its travel. Using a feeler gauge or a dial indicator, measure the end-play at the front of the rear main bearing. End-play may also be measured at the thrust bearing.
Install a new rear main bearing oil seal in the cylinder block and main bearing cap. Continue to reassemble the engine.