Main Bearing-Fitting
CRANKSHAFT MAIN BEARINGS
Fig. 26
Bearing caps are not interchangeable and should be marked at removal to insure correct assembly (Fig. 26). Upper and lower bearing halves are NOT interchangeable. Lower main bearing halves of 1, 2, 4, 5 and 6 are interchangeable. Upper main bearing halves of 1, 2, 4, 5 and 6 are interchangeable.
CRANKSHAFT MAIN JOURNALS
The crankshaft journals should be checked for excessive wear, taper and scoring. Limits of taper or out-of-round on any crankshaft journals should be held to 0.013 mm (0.0005 inch). Journal grinding should not exceed 0.508 mm (0.020 inch) under the standard journal diameter. DO NOT grind thrust faces of No. 3 main bearing. DO NOT nick crank pin or bearing fillets. After grinding, remove rough edges from crankshaft oil holes and clean out all passages.
CAUTION: With the forged crankshafts it is important that the final paper or cloth polish after any journal regrind be in the same direction as normal rotation in the engine.
Fig. 27
Upper and lower No. 3 bearing halves are flanged to carry the crankshaft thrust loads and are NOT interchangeable with any other bearing halves in the engine (Fig. 27). All bearing cap bolts removed during service procedures are to be cleaned and oiled before installation. Bearing shells are available in standard and the following undersizes: 0.025 mm (0.001 inch), 0.051 mm (0.002 inch), 0.076 mm (0.003 inch), 0.254 mm (0.010 inch), 0.305 mm (0.012 inch) and 0.508 mm (0.020 inch). Never install an undersize bearing that will reduce clearance below specifications.
CRANKSHAFT MAIN BEARINGS - CRANKSHAFT NOT REMOVED
Bearing caps are not interchangeable and should be marked at removal to insure correct assembly. (Fig. 26) Upper and lower bearing halves are NOT interchangeable. Lower main bearing halves of 1, 2, 4, 5 and 6 are interchangeable. Upper main bearing halves of 1, 2, 4, 5 and 6 are interchangeable.
(1) Remove the oil pan and windage tray, identify bearing caps before removal.
Fig. 28
(2) Remove bearing caps one at a time. Remove upper half of bearing by inserting Special Main Bearing Tool C-3059 (Fig. 28) into the oil hole of crankshaft.
(3) Slowly rotate crankshaft clockwise, forcing out upper half of bearing shell.
CAUTION: When cleaning the gasket surfaces use a gasket remover to soften the old gasket material. Also, to avoid damage to the mating surfaces, do not use a metal scraper. Instead use a plastic or wooden scraper.
INSTALLATION
NOTE: Only one main bearing should be selectively fitted while all other main bearing caps are properly tightened.
When installing a new upper bearing shell, slightly chamfer the sharp edges from the plain side.
(1) Start bearing in place, and insert Main Bearing Tool C-3059 into oil hole of crankshaft (Fig. 28).
(2) Slowly rotate crankshaft counterclockwise sliding the bearing into position. Remove Special Main Bearing Tool C-3059.
(3) Install each main cap and tighten all bolts finger tight.
(4) Tighten main cap bolts in the following torque sequence:
Fig. 29
(5) Step 1 Tighten only the center main caps bolts in the sequence order shown in (Fig. 29) to 20 Nm (15 ft. lbs.). This will seat the bearing caps onto the engine block.
(6) Step 2 To ensure correct thrust bearing alignment the following procedure must be done:
(7) Move crankshaft all the way to the rear of its travel.
(8) Then, move crankshaft all the way to the front of its travel.
(9) Wedge an appropriate tool between the rear of the cylinder block and rear crankshaft counterweight. This will hold the crankshaft in it's most forward position.
(10) Step A1 Tighten the A1 bolts to 61 Nm (45 ft. lbs.) in the sequence order shown in (Fig. 29).
(11) Step A2 Tighten the A2 bolts to 115 Nm (85 ft. lbs.) in the sequence order shown in (Fig. 29).
(12) Step A3 Tighten the A3 Bolts to 54 Nm (40 ft. lbs.) in the sequence order shown in (Fig. 29).
(13) Remove the holding tool.
CRANKSHAFT OIL CLEARANCE
Fig. 30
(1) Measure the journal outside diameter as shown in (Fig. 30). Refer to Engine, Specifications for crankshaft specifications.
PLASTIGAGE (OIL CLEARANCE) MEASUREMENT
(1) Remove oil from journal and bearing shell.
(2) Install crankshaft.
Fig. 31
(3) Cut Plastigage to same length as width of the bearing and place it in parallel with the journal axis (Fig 31)
(4) Install the main bearing cap carefully and tighten the bolts to specified torque.
CAUTION: Do not rotate crankshaft or the Plastigage will be smeared.
(5) Carefully remove the bearing cap and measure the width of the Plastigage at the widest part using the scale on the Plastigage package (Fig. 31). For proper clearances, refer to Specification in Crankshaft, Engine. If the clearance exceeds the specified limits, replace the main bearing(s) and if necessary, have the crankshaft machined to next undersize. Also refer to Measuring Main and Connecting Rod Bearing Clearance in Service Procedures.
CAUTION: Do not rotate crankshaft or the Plastigage may be smeared.