Connecting Rod Bearing Service

NOTE: Following procedures are with oil pan and cylinder heads removed. Main and rod bearing size is indicated by letter stamped into bearing tang or actual bearing size stamped opposite of tang. Bearing marks are as follows: A = .0005", B = .0010", and C = .0015". During production, .009" undersize bearings may have been installed for close tolerances on some journals.

Remove connecting rod bearing caps and 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.
Measure outside diameter of rod bearing journals to determine if out-of-round or tapered. Standard journal out-of-round is .0005" (.013 mm) and must not exceed .0010" (.025 mm). Standard journal taper is .0005" (.013 mm) and must not exceed .0010" (.025 mm). If journals are more than .0010" (.025 mm) out-of-round or tapered, crankshaft must be reconditioned or replaced.
When checking connecting rod clearances, do not support crankshaft. Instead, turn crankshaft until rod to be checked starts moving up, thus unloading lower bearing.
Cut Plastigage to same length as width of rod bearing. Place in bearing cap, parallel with crankshaft (not over oil hole or groove). Install rod bearings and cap and tighten. Always install caps with markings in original positions.
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 exceeds specifications, replace bearing.
NOTE: If clearance cannot be brought within specifications with service bearings, grind crankshaft to next undersize. If already ground to maximum undersize, replace crankshaft.
Selective fitting is required on each connecting rod. Service bearings are available in standard size, .001" and .002" undersize for new or used standard size crankshaft. Bearings of .010" and .020" undersize are for use with reconditioned crankshafts. After inspection and/or replacement, coat bearing surfaces with oil. Tighten connecting rod bearing caps in two steps.
NOTE: Connecting rod bearing cap and rod identification numbers must remain on same side. Always replace the bearings in pairs. Never use new bearing in combination with used bearing. Never file or grind connecting rods or caps when fitting bearings.
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.
Check connecting rod side clearance with dial gauge indicator resting against rod cap. Pull cap toward front of engine and zero gauge. Push cap toward rear of engine and compare readings. If excessive, replace rod and cap.
Standard connecting rod side clearance is .006-.014" (.15-.36 mm). 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.
During assembly, ensure oil hole in bearing aligns with oil hole in connecting rod. Check bearing tangs are seated in appropriate slots in rod and cap. Ensure rod bolt heads are properly seated in rod.