Cylinder Block: Connecting Rod Bearings

NOTE: Following procedures are with oil pan and cylinder head removed. Selective fit bearings are used in this engine. DO NOT scrape gum or varnish deposits from bearing shells. Clean inserts and caps thoroughly in solvent. DO NOT file or lap bearing caps or use bearing shims to obtain proper bearing clearance.

1. Remove connecting rod bearing caps. Mark rods and caps for proper installation. Inspect each bearing for peeling, melting, seizure or improper contact. Replace defective bearings. Use Plastigage method for bearing clearance check.
2. Measure outside diameter of crankshaft connecting rod bearing journals to determine if out-of-round or tapered. Journal out-of-round must not exceed .0006" (.015 mm) per inch. Journal taper must not exceed .0006" (.015 mm).
   CAUTION: If bearing is fitted to out-of-round crankpin, be sure to fit to maximum diameter of crankpin. If bearing is fitted to minimum diameter, interference between bearing and crankpin will result causing rapid bearing failure.
3. When checking connecting rod clearances, crankshaft does not have to be supported. Instead, turn crankshaft until connecting rod to be checked starts moving toward top of engine, thus unloading lower bearing.
4. Cut Plastigage (D81L-6002-B) to width of rod bearing. Place Plastigage about .25" (6.35 mm) off-center (not over oil hole or groove). Place in bearing cap, parallel with crankshaft. Install rod bearing and cap. Tightening in two steps to specifications. Always install cap with markings in original position.
5. Do not turn crankshaft with Plastigage installed. Remove rod bearing cap from crankshaft and measure Plastigage at its widest part (using scale on Plastigage package). If clearance is found to be excessive, new bearing will be required. See Fig 1 .
6. Service bearings are available in standard size and .0005" and .0010" undersize for use with new and used standard size crankshafts. After inspection and/or replacement, coat bearing surfaces with heavy engine oil.
   NOTE: Connecting rod bearing cap and rod identification numbers must remain on same side. Always replace bearings in pairs. Never combine new and used bearings.
7. Check for shiny surface on either side of piston pin boss, indicating bent connecting rod. Twisted rods will not create identifiable wear patterns, but will disturb the action of entire crankshaft assembly and may cause excessive oil consumption.
8. Check connecting rod side clearance with dial indicator contact point resting against rod cap. Pull cap toward front of engine and zero dial indicator. Push cap toward rear of engine and compare reading to specification. If excessive, replace connecting rod and cap.
9. If side clearance is less than specification, remove rod and cap. Check for scratches, burrs, nicks or dirt between crankshaft and rod. Dress minor imperfections with oil stone.
10. During assembly, ensure oil hole in bearing aligns with oil hole in connecting rod. Ensure bearing tangs are seated in appropriate slots in rod and cap. Ensure connecting rod bolt heads are properly seated in connecting rod. Tighten connecting rod bolts in two steps.

Fig 1: Using Plastigage to Check Bearing Clearance DO NOT turn crankshaft or Plastigage will smear.