Connecting Rod Bearing Clearance Installation and Inspection

GENERAL INFORMATION

WARNING: This description applies only to standard-size connecting rod bearings. Replacement connecting rod bearing shells are not divided into size groups.

New connecting rod bearings are selected using the size group codes stamped on the crankshaft. The size group codes are marked either on the crankshaft web next to the No. 1 cylinder journal (timing chain side), or on the web next to the No. 4 cylinder journal (flywheel or driveplate side). A four-digit code indicates the size groups of the crankshaft connecting rod journals; the first digit refers to the No. 1 cylinder journal and the fourth digit to the No. 4 cylinder journal. A five-digit code refers to the size groups of the crankshaft main journals (see subsection 3.2.2.8.2).

To select connecting rod bearing shells, determine the size group of the crankshaft connecting rod journal for the given cylinder, then use the supplied table to determine the required shell by the color code, which is marked as a dot on the side surface of the shell.

Crankshaft code / Color code of bearing shell size group: 0 - black; 1 - brown; 2 - green. Checking connecting rod bearing clearance

PROCEDURE

1. Clean the outer surface of the connecting rod bearing inserts and the bores for the inserts in the connecting rods and rod caps.

2. Press the bearing shells into place, installing the upper and lower shells. Make sure the tabs on the bearing shells engage the recesses in the connecting rod and the connecting rod cap (indicated by arrows).

3. When installing the shells, do not touch the working surfaces of the bearing shells with your fingers. Make sure the lubrication hole in the upper connecting rod bearing shell aligns exactly with the hole in the connecting rod. If the clearance check is performed with the old shells, make sure the shells are installed in their original positions.

4. The connecting rod bearing clearance can be checked in two ways. For the first method, assemble the caps with the connecting rods and bearing shells, observing the correct orientation of these parts. Tighten the connecting rod cap nuts to the specified torque and measure the inside diameter of each assembled pair of shells with a dial bore gauge or inside micrometer. The bearing clearance is determined as the difference between the inside diameter of the assembled connecting rod bearings and the diameter of the corresponding crankshaft connecting rod journal.

5. The second method (more accurate) uses Plastigage, round-section plastic gauge wire, laid on the carefully cleaned surfaces of the connecting rod journals.

6. Install the connecting rod bearings, orienting them correctly. Place a length of gauge wire on each crankshaft connecting rod journal.

7. Clean the surfaces of the connecting rod bearing shells and install the connecting rods onto the corresponding crankshaft journals. Install the connecting rod bearing caps, aligning them using the marks present or the marks made during disassembly.

8. Tighten the cap nuts (see below). When tightening, do not allow the wire to shift, and do not rotate the crankshaft.

9. Remove the connecting rod caps without rotating the crankshaft or displacing the gauge wire. Compare the width of the flattened wire with the scale on the packaging and determine the main bearing clearance.

10. If the clearance differs from the specification, the cause may be incorrect selection of connecting rod bearing shells (or excessive wear if used shells were checked). Before concluding that the shells must be replaced, make sure there was no dirt or oil between the cap or rod surfaces and the shell during measurement. If the flattened wire is wider at one edge, this indicates taper of the connecting rod journal.

11. If the clearance differs from the specification when measured with the old bearings, repeat the measurements with new bearings. If the clearance still exceeds the specification with new bearings, contact the dealer service department or a specialist familiar with this engine for advice on further action. It may be necessary to regrind the crankshaft connecting rod journals and install undersize bearings.

12. If necessary, purchase bearings of the correct size group and repeat the connecting rod bearing clearance measurement procedure.

13. Upon completion, scrape off the remaining Plastigage with a fingernail or a wooden stick from the crankshaft main journals, taking care not to damage their surface.

Installation of Piston and Connecting Rod Assemblies. The following description assumes that the assembly is performed after the crankshaft assembly has been installed with all main bearings and caps (with the cap frame).

PROCEDURE

1. Make sure the connecting rod bearings are installed correctly (see steps 4 and 5). If new bearings are being installed, carefully remove the preservative oil by washing them in kerosene. Wipe the connecting rods and bearings dry with lint-free cloth.

2. Make sure the piston ring end gaps are correctly positioned and compress the rings using a special ring compressor.

3. Lubricate the cylinders, pistons and rings, then lay out the piston and connecting rod assemblies in the same sequence in which they will be installed in the engine.

4. Begin assembly with cylinder No. 1. Make sure the piston ring end gaps are correctly positioned (see subsection 3.2.2.12) and compress the rings using a special ring compressor.

5. Insert the piston and connecting rod assembly into cylinder No. 1. Orient the piston so that the mark on the piston crown (arrow or line) faces the timing chain cover side. Gently tap the piston with the handle of a hammer or a wooden block until the piston enters the cylinder and the piston crown is flush with the cylinder block deck surface.

6. Make sure the connecting rod bearings are installed correctly and apply plenty of oil to the bearings and the crankshaft connecting rod journal. Carefully pull the connecting rod onto the crankshaft journal, taking care not to damage the cylinder surface. Install the connecting rod cap with bearing and hand-tighten the nuts. Note that the marks on the connecting rod and the connecting rod cap must align (this means the bearing locating tabs are opposite each other).

7. Tighten the connecting rod cap nuts to Stage 1 torque using a torque wrench and socket (photo left). Then turn the nuts through the Stage 2 angle, or if no angle gauge wrench is available, tighten to Stage 2 torque (photo right).

8. Turn the crankshaft and check that it rotates freely. If new parts are installed, a noticeable constant resistance to rotation should be felt, but the crankshaft must turn smoothly without binding.

9. Install the remaining pistons and connecting rods in the same manner.

10. Install the cylinder head, the camshaft drive chain (or chains) and the oil pan.