Fitting Crankshaft Main Bearings

Fitting Crankshaft Main Bearings

This article is only for Chevy Old Models 

After the three upper halves of the bearings have been fitted Install the crankshaft

Smear a thin coat of Prussian Blue on each bearing surface of the crankshaft.

Place the thin metal shims between the upper and lower bearing caps.

Replace all three bearings and tighten the bearing caps. Place a bar between the flywheel bolts, Turn the crankshaft several times.

Remove bearing caps and examine bearings for blue spots.

If the bearing does not touch or fit snugly on the shaft it may be necessary to remove equal number of shims from each side. Scrape out the blue spots.

Repeat the operations until the bearing surface is smooth and touches the crankshaft at all points.

After the bearing surfaces conform to those of the crank shaft, remove all Prussian blue from the shaft, lubricate the bearings well and install the bearing caps.Adjust each bearing separately to get the proper tension.Then tighten the caps down permanently and insert the cotter pins in the castle nuts.


Fitting Crankshaft Main Bearings With an Aligning Reamer

A very satisfactory method of fitting crankshaft main bearings is with the use of a reaming tool.

The upper and lower halves of the bearings are tightened in place.

The reaming fixture is adjusted to the case and the bearings are reamed to the exact size of the crankshaft.

The crankshaft gear is placed on the reamer bar and meshes with the cam shaft gear when the reamer is being adjusted to insure a proper mesh of the gears.

After the bearings have been reamed, each bearing cap should be drawn down separately and sufficient shims used to get the proper tension.


End Play in Crankshaft

The end play in the crankshaft is governed by the bronze flange on the center crank shaft bearing, and when installing new bearings or refitting an old bearing care should be taken to see that about .006 of an inch clearance is allowed at this point.

To determine the clearance move the crank shaft backward and forward with a screwdriver or bar.Too much end play will often cause a pound or knock when the motor is running idle.


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Fitting Crankshaft Main Bearings article Source – This article courtesy should goes to : Chevrolet Repair Guide of 1923 by Chevrolet Motor Company.