Figure 12-24 Rear Cylinder Block Oil Gallery Plugs Clean • Sealing material from mating surfaces. • Boil cylinder block in caustic solution. Flush with clean water or steam. • Cylinder bores. • Threaded holes. • Oil galleries and passages. • Scale deposits from coolant passages. • Spray or wipe cylinder bores and machined surfaces with engine oil. Inspect • All expansion plugs for lack of fit or leakage. • Valve lifter bores for deep scratches and deposits. • Cracks in the block. - Cylinder walls. - Coolant jackets. - Engine mount bosses. - Main bearing webs. • Main bearing bores and caps. - All main bearing bores should be rounded and uniform in ID at all of the bearing supports.
- The area were the main bearing inserts contact the main bearing bore should be smooth. - If a main bearing cap is found to be damaged, replace the cap and line-bore the block. • Cylinder head mounting surface for flatness, using a precision straightedge and feeler gage (figure 12-25). - Set the straightedge on the sealing surface to be inspected. - Take the feeler gage and at various locations, check the gap between the straightedge and the sealing surface. Figure 12-25 Measuring Cylinder Block Surface Flatness - If the gap is greater than 0.05 mm (0.002 in.) within 152 mm (6 in.) at any sealing location, the block must be replaced.
- If the gap is found to be less than 0.05 mm (0.002 in.) at any sealing location and a cause for leakage is suspected, then the minor irregularities may be carefully machined from the block. • Oil pan, timing cover, and intake manifold mounting surfaces for nicks. Minor irregularities may be cleaned up with a flat file. Cylinder Bore Inspect • Cylinder bores for scoring or other damage. • Cylinder bore taper and out-of-round. Measuring Cylinder Bore Taper and Out- Of-Round Figure 12-26 Tool Required: J 8087 Cylinder Bore Gage (or equivalent) IMPORTANT:
If one or more cylinder bores are rough, scored or worn beyond limits, it will be necessary to smooth or true up such bores to fit new pistons. No attempt should be made to cut down oversize pistons to fit cylinder bores as this will destroy the surface treatment and affect the weight. The smallest possible oversize pistons should be used and the cylinder bores should be honed to size for proper clearances. G643 (E) Service Manual Chapter 3. Engine Mechanical System 73