Lower Crankcase (Oil Manifold)

Main Bearings:

Shell type main bearings of steel backed aluminum are used at all positions. The lower bearing halves are all interchangeable. as are all of the upper halves except for the bearings in the # 3 position as this is the thrust bearing. Maximum crank shaft end play is 0.5 mm (0.019 in.).

Separating Crankcase Halves:

REMOVE OR DISCONNECT
1. With engine on engine stand remove the following components:
^ Engine oil pan.
^ Oil pump pickup.
^ Oil scraper I baffle.
^ Main bearing bolts.
^ Oil manifold bolts.
^ Oil manifold.
^ Upper / lower crankcase bolts.
2. Working on either side of crankcase separate crankcase halves by alternately prying in grooves provided until lower crankcase is free of dowel pin.

NOTICE: Use a plastic pry tool when prying case halves apart to prevent damage to the Lower Crankcase surface. Do not keep pushing your pry tool in the crankcase as the Upper and Lower Crankcase halves separate. This may damage the sealing surface.

3. Lower crankcase.

Note: Upper-to-lower crankcase seal may be reused unless it is damaged or comes out of its groove in the upper crankcase.

4. Rear main seal and discard.
5. Lower main bearing from lower crankcase.

MEASURE
^ With the engine in the condition described above main bearing clearance can be measured with the aid of plastic gauging material. Use gauging material with a working range of 0.025 mm to 0.070 mm (0.001 to 0.003").

1. Wipe oil from crankshaft journal(s) and bearing insert(s).
2. Place a length of plastic gauging material all the way across the journal(s) to be measured.

IMPORTANT
^ When using plastic gaging material, plastic material and part being measured must both be at room temperature. If parts are excessively warm, an incorrect reading may result. Fresh plastic gaging material is recommended for greatest accuracy.

3. Reinstall lower crankcase and oil manifold.

Fig. 19 Main Bearing Cap Bolt Tightening Sequence:

4. Install 20 main bearing bolts and torque bolts to 20 Nm + 65°(15 lb. ft. + 65°)in sequence, bolts 1 through 20.
5. Determine clearance by comparing width of flattened plastic gauging material at its widest point with graduation on gaging material container.

Note: If bearing clearance is greater than 0.070 mm (0.003") and new bearings do not reduce the clearance to 0.015 to 0.055 mm (0.0005" to 0.002") a new crankshaft will be required. Undersized bearings are not available and no crankshaft grinding is allowed.

INSTALL OR CONNECT
1. Clean lower crankcase crank bore. Be sure to clean all oil from behind the bearing. Install lower crankcase main bearings - identified by NO groves or holes - into position in lower crankcase. The bearing must fit flush with lower crankcase.
2. Clean the upper main bearing crank bore. Install the upper main bearing into position. Be sure the upper bearing insert contains the oil transfer hole and groove. Roll bearing into position so that lock engages crank slot. The bearing must fit flush with the upper crankcase.
3. Apply a liberal amount of GM Prelube, part number 1052367 or engine oil to upper and lower bearing surfaces.

Crankcase Half Seals:

4. Inspect upper crankcase seal to assure that it is in position in crankcase. Seal must not be torn. nicked or out of groove over its entire length on both sides of crankcase. To replace seal proceed as follows:
A. Clean block groove.
B. Start seal at both ends and work seal into groove towards center.
5. Lower crankcase over dowels. Wiggle into installed position.
6. Oil manifold.

Main Bearing Bolts:

7. Twenty main bearing bolts. Inboard bolts have stud head.
8. Ten oil manifold bolts.
9. Eight upper-to-lower crankcase bolts.

TIGHTEN
^ Main bearing bolts to 20 Nm + 65° (15 lb. ft. + 65°) in sequence.
^ Oil manifold bolts to 10 Nm (7 lb. ft.).
^ Upper-to-lower crankcase bolts to 30 Nm (22 lb. ft.).

MEASURE
^ Crankshaft end play. Gently force crankshaft to extreme front and rear position. Monitor movement of dial indicator on nose of crankshaft. End play should not exceed 0.50 mm (0.019").

Oil Scraper / Baffle:

10. Oil scraper baffle and ten nuts. Tighten nuts to 25 Nm (18 lb. ft.).
11. Oil pump pickup using new 0-ring. Tighten bolts to 10 Nm (7 lb. ft.).
12. Engine oil pan.
13. Rear main seal.
14. Primary cam drive chain.