Connecting Rod Bearings

Replace connecting rod bearings on a 1966 Corvette 327ci V8, requiring engine disassembly from below, crankshaft inspection, bearing installation, and torque-to-yield rod bolt replacement.

Warnings

Tools required

Parts

• Connecting rod bearing set (8 rods, standard or oversized as measured) × 1 — Use OEM specification or Perfect Circle/Clevite CB-743P (standard)
• Connecting rod bolts (if reusing bolts, inspect for stretch) × 16 — Use OEM specification
• Oil pan gasket × 1 — Use OEM specification or Fel-Pro OS30093R
• Oil pump pickup tube O-ring × 1 — Use OEM specification
• Timing cover gasket × 1 — Use OEM specification
• Harmonic balancer seal × 1 — Use OEM specification
• Oil filter × 1 — Use OEM specification or AC PF-25
• Oil pan drain plug gasket × 1 — Use OEM specification
• RTV silicone sealant (timing cover) × 1 — Permatex Ultra Black 82180

Fluids

• 5W-30 Conventional Engine Oil — 5 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Disconnect negative battery cable
3. Allow engine to cool completely (minimum 4 hours)
4. Drain engine oil completely into appropriate container
5. Remove oil filter
6. Remove distributor cap and mark distributor rotor position for reinstallation
7. Remove spark plugs to ease crankshaft rotation
8. Raise vehicle and support securely on 4 jack stands at frame rails
9. Remove exhaust headers or manifolds (both sides)
10. Place wooden blocks or support under transmission pan to support engine weight

Procedure

1. 1

   Remove oil pan
   Unbolt and remove the oil pan. Remove the 18 oil pan bolts using a 7/16-inch socket. The front 2 bolts secure the timing cover to the oil pan. Gently pry pan loose if stuck, being careful not to damage sealing surfaces. Remove oil pan gasket and scrape all old gasket material from block and pan surfaces using a plastic scraper.
2. 2

   Inspect oil pump and remove pickup
   Remove the 2 oil pump pickup tube mounting bolts using a 9/16-inch socket. Remove the pickup tube and screen assembly. Inspect screen for debris or metal particles indicating bearing failure extent. Clean screen thoroughly and set aside for reinstallation.
3. 3

   Remove timing cover (partial)
   Remove the harmonic balancer using a puller tool. Remove the timing cover bolts (except the 2 lower bolts that mate with oil pan). Pull timing cover forward approximately 1 inch to provide clearance for piston removal if needed. This allows rod/piston assemblies to clear the crankshaft counterweights during removal.
4. 4

   Mark and identify connecting rods
   Rotate crankshaft to bring cylinder 1 to bottom dead center. Using a permanent marker or stamping set, clearly mark each connecting rod and cap with cylinder number (1-8) and orientation (mark facing front or camshaft side). The factory often stamps rods, but marks may be worn. Verify marks are visible and unambiguous. Cylinder 1 is front driver side, numbering goes 1-3-5-7 on driver side, 2-4-6-8 on passenger side.
5. 5

   Remove connecting rod caps
   Using a 9/16-inch socket and breaker bar, remove both rod cap bolts from cylinder 1. Tap the rod cap gently with a rubber mallet to break it free. Remove cap and bearing insert, keeping them together and labeled. Repeat for all 8 cylinders, keeping each rod cap and bearing set together and clearly labeled.
6. 6

   Remove ridge at top of cylinder (if present)
   Check cylinder 1 for a carbon/wear ridge at the top of the bore. If present (common on engines with significant mileage), use a ridge reamer to carefully remove the ridge. This prevents piston ring damage during removal. Repeat for any cylinder showing a ridge. Clean any cutting debris thoroughly before proceeding.
7. 7

   Push pistons up and remove rod bearings
   Using a wooden hammer handle or plastic rod, gently push the rod/piston assembly for cylinder 1 upward into the cylinder bore, just far enough to access the rod bearing. Remove the upper bearing shell from the rod. Cover the rod bolts with rubber hose or tape to prevent crankshaft journal damage. Repeat for all 8 cylinders, keeping bearings labeled by cylinder number.
8. 8

   Inspect and measure crankshaft journals
   Clean all 4 rod journals on the crankshaft with solvent and lint-free cloth. Inspect each journal carefully for scoring, discoloration, or roughness. Using a micrometer, measure each journal diameter in at least 2 positions (90 degrees apart) to check for out-of-round. Standard 327 rod journal diameter is 2.300 inches. Maximum out-of-round tolerance is 0.001 inch. Maximum taper tolerance is 0.001 inch. If journals are scored or exceed tolerance, crankshaft must be removed and reground to the next undersize (0.010, 0.020, or 0.030 inch undersize).
9. 9

   Polish crankshaft journals (if acceptable)
   If journals pass inspection with only minor glazing or light surface imperfections, polish each journal using crocus cloth wrapped around the journal. Rotate crankshaft while moving cloth back and forth to achieve a uniform crosshatch pattern. Clean journals thoroughly with solvent after polishing to remove all abrasive residue. Journals should feel glass-smooth to fingernail test.
10. 10

    Measure connecting rod bearing clearances
    Install new bearing shells (dry, no lubricant) into connecting rod and cap for cylinder 1, ensuring bearing tang locks into rod and cap notches. Place a strip of Plastigage across the full width of the crankshaft journal. Install the rod cap with bearings in correct orientation and torque rod bolts to 45 ft-lb. Do not rotate crankshaft with Plastigage installed. Remove cap carefully and measure the flattened Plastigage width using the gauge on the Plastigage package. Standard bearing clearance for the 327 is 0.0007-0.0027 inch. If clearance exceeds 0.004 inch, use next undersize bearing or machine crankshaft. Repeat for all 8 rods.
11. 11

    Clean all components thoroughly
    Remove all Plastigage residue from bearings and journals using solvent. Clean connecting rods, caps, bolts, and crankshaft journals with brake cleaner and lint-free shop towels. Inspect rod bolts for necking, stretching, or thread damage. Replace bolts if any deformation is visible or if they have been torqued previously (many 327 rod bolts are torque-to-yield design).
12. 12

    Install new bearing shells with assembly lube
    Install new bearing shells into each connecting rod and cap, ensuring tangs are properly seated in notches. Apply a thin coat of engine assembly lube to the inside surface of each bearing. Do not over-lubricate. Push each piston/rod assembly back down until the rod bearing seats on the crankshaft journal. Ensure rod bolt protectors remain in place.
13. 13

    Install connecting rod caps and torque bolts
    Install connecting rod cap for cylinder 1 in the correct orientation (match marks made earlier). Install both rod bolts and hand-tighten. Using a torque wrench, torque both bolts to 45 ft-lb in two stages: first to 20 ft-lb, then to final 45 ft-lb. After torquing, check that the rod can move slightly side-to-side on the journal (0.006-0.014 inch side clearance is normal). Repeat for all 8 cylinders in sequence. After all rods are torqued, rotate crankshaft by hand through 2 complete rotations to verify smooth operation with no binding or tight spots.
14. 14

    Reinstall oil pump pickup and timing cover
    Reinstall the oil pump pickup tube with new O-ring, torquing the 2 mounting bolts to 25 ft-lb. Push timing cover back into position and install all timing cover bolts except lower 2. Apply thin bead of RTV sealant where timing cover meets block at the oil pan surface. Install new front seal into timing cover if removed. Reinstall harmonic balancer, torquing center bolt to 60 ft-lb.
15. 15

    Install oil pan with new gasket
    Position new oil pan gasket on block, aligning all bolt holes. Apply small dabs of RTV sealant at the front corners where timing cover meets block and at rear main cap corners. Lift oil pan into position, starting all 18 bolts by hand. Torque oil pan bolts in a spiral pattern from center outward to 12 ft-lb. Do not overtighten, as this can distort the pan and cause leaks.

Reassembly

1. Reinstall exhaust headers or manifolds with new gaskets
2. Reinstall spark plugs, torquing to 25 ft-lb
3. Reinstall distributor, aligning rotor to original marked position
4. Reinstall distributor cap and plug wires in correct firing order (1-8-4-3-6-5-7-2)
5. Lower vehicle from jack stands
6. Install new oil filter
7. Reconnect negative battery cable
8. Fill engine with 5 quarts of 5W-30 conventional motor oil
9. Prime oil system by cranking engine with ignition disabled (remove coil wire) until oil pressure gauge shows pressure or oil light goes out
10. Start engine and check for oil leaks at pan gasket and timing cover
11. Allow engine to idle for 5 minutes, monitoring oil pressure (should be 35-40 psi at idle when warm)
12. Shut off engine, wait 5 minutes, and recheck oil level; add oil if needed

Verification

• Check for oil leaks around oil pan, timing cover, and all gasket surfaces after initial startup
• Verify oil pressure reads 35-40 psi at hot idle and 50-60 psi at 2000 RPM
• Listen for any abnormal knocking, ticking, or rattling noises from lower engine during idle and light acceleration
• After 50-100 miles of operation, recheck oil level and inspect for leaks
• Monitor oil pressure gauge during first 500 miles; pressure should remain stable and consistent

More procedures for this vehicle