PISTONS, CONNECTING RODS, PISTON RINGS AND CYLINDER BORES

Pistons and connecting rods - remove

1. Remove cylinder head(s).
2. Remove big-end bearings.
3. Remove carbon ridge from top of each cylinder bore.
4. Suitably identify each piston to its respective cylinder bore.
5. Push connecting rod and piston assembly to top of cylinder bore and withdraw assembly.
6. Remove plastic tubing from connecting rod bolts.
7. Repeat above procedure for remaining pistons.

Piston rings - remove

1. Using a suitable piston ring expander, remove piston rings.
2. Remove carbon from piston ring grooves.

NOTE: Use an old broken piston ring with a squared off end.
CAUTION: Do not use a wire brush.

Piston rings - inspection

1. Temporarily fit new compression rings to piston.

NOTE: The ring marked ’TOP’ must be fitted, with marking uppermost, into second groove. The chrome ring fits into top groove and can be fitted either way round.

2. Check compression ring to groove clearance:
Top compression ring A = 0.05 to 0.10 mm.
2nd compression ring B = 0.05 to 0.10 mm.
3. Insert new piston ring into relevant cylinder, held square to bore with piston, and check ring gaps.
Top compression ring = 0.44 to 0.57 mm.
2nd compression ring = 0.44 to 0.57 mm.
Oil control ring rails = 0.38 to 1.40 mm.
4. Use a fine-cut flat file to increase gap if required. Select a new piston ring if gap exceeds limit.

Pistons - remove

1. Clamp hexagon body of LRT-12-013 in vice.
2. Screw large nut back until flush with end of centre screw.
3. Push centre screw forward until nut contacts thrust race.
4. Locate piston adapter LRT-12-014 with its long spigot inside bore of hexagon body.
5. Fit parallel sleeve, grooved end first, onto centre screw and smear outside diameter with engine oil.
6. Locate piston and connecting rod assembly on centre screw and up to adapter LRT-12-014.
7. Fit remover/replacer bush of LRT-12-014 on centre screw with flanged end away from gudgeon pin.

8. Screw stop nut onto centre screw leaving clearance A, between nut and remover/replacer bush. Clearance A = 3 mm.
9. Lock the stop nut securely with lockscrew.
10. Push connecting rod to right to locate end of gudgeon pin in adapter LRT-12-014.
11. Ensure remover/replacer is located in gudgeon pin bore of piston.
12. Screw large nut up to thrust race.
13. Hold lockscrew and turn large nut until gudgeon pin is withdrawn from piston.
14. Dismantle tool and remove piston, connecting rod and gudgeon pin.
15. Repeat above operation for remaining pistons.

Pistons - inspection

1. Clean carbon from pistons
2. Inspect pistons for distortion and cracks.
3. Measure piston diameter at 90° to gudgeon pin axis and 8 mm from bottom of skirt. The piston must be 0.018 mm to 0.033 mm smaller than
cylinder bore.

 

Cylinder bore - inspection

1. Measure cylinder bore wear in two axis 40 to 50 mm from top of bore.
Piston to cylinder bore clearance = 0.018 to 0.033 mm.

NOTE: Pistons are available in service standard size and 0.508 mm oversize. Service standard size pistons are supplied 0.0254 mm oversize. When fitting new service standard size pistons, check for correct piston to bore clearance, hone bore if necessary.

CAUTION: The temperature of piston and cylinder block must be the same to ensure accurate measurement. When reboring cylinder block, the crankshaft main bearing caps must be fitted and bolts tighten to correct torque.

2. If only new piston rings are to be fitted, break cylinder bore glazing using a fine grit, to produce a 60° cross-hatch finish.

CAUTION: Ensure all traces of grit are removed after above operation.

Connecting rod - inspection

1. Check alignment of connecting rod.

Pistons - refit

CAUTION: On later 4.2L engines the piston has a 0.5 mm offset gudgeon pin which can be identified by an arrow mark on the piston crown. This arrow MUST always point to the front of the engine.

1. 4.2L engine only: Assemble pistons to connecting rods with arrow on piston pointing towards domed shaped boss on connecting rod for RH bank of cylinders, and arrow pointing away from dome shaped boss for LH bank of cylinders.

2. Clamp hexagon body of LRT-12-013 in vice.
3. Remove large nut and pull the centre screw 50 mm out of hexagon body.
4. Locate piston adapter LRT-12-014 with its long spigot inside bore of hexagon body.
5. Fit parallel sleeve, grooved end last, up to shoulder on centre screw.
6. Lubricate gudgeon pin and bores of connecting rod and piston with graphited oil.
7. Locate connecting rod and piston to centre screw with connecting rod entered on sleeve up to groove.

8. Fit gudgeon pin onto centre screw and into piston bore up to connecting rod.
9. Fit remover/replacer bush with flanged end towards gudgeon pin.
10. Screw the stop nut onto centre screw and position piston against face of adaptor LRT-12-014.
11. Lubricate centre screw threads and thrust race with graphited oil, fit, and screw large nut up to thrust race.
12. Adjust stop nut leaving clearance B, between nut and remover/replacer bush. Clearance B = 0.8 mm.
13. Lock the stop nut securely with lockscrew.
14. Set torque wrench to 16 Nm, and using socket on large nut, pull gudgeon pin in until flange of remover/replacer bush is distance C from face of piston.
Distance C = 4 mm.

CAUTION: Flange of remover/replacer must not be allowed to contact piston. If torque figure is not achieved during above operation, fit of gudgeon pin to connecting rod is not acceptable and necessitates renewal of components. The centre screw and thrust race must be kept well lubricated throughout operation.

15. Dismantle tool, remove piston, check no damage has occurred during pressing and piston moves freely on gudgeon pin.
16. Repeat above operation for remaining pistons.

Pistons and connecting rods - refit

1. Fit oil control ring rails and expander, ensuring ends butt and not overlap.
2. Fit ring marked ’TOP’ with marking uppermost into second groove.
3. Fit top compression ring into groove either way round.
4. Position oil control expander ring joint and ring rail gaps all at one side, between gudgeon pin and piston thrust face. Space gaps in ring rails approximately 25 mm each side of expander ring joint.
5. Position compression rings with ring gaps on opposite sides of piston between gudgeon pin and piston thrust face.
6. Fit big-end bearing shell to connecting rod.
7. Lubricate big-end bearing shell, piston rings and gudgeon pin with engine oil.
8. Lubricate cylinder bores and crankshaft big-end journals with engine oil.

 

Fit ring clamp to piston and compress piston rings.
10. Fit plastic tubing to connecting rod bolts.
11. Insert connecting rod and piston assembly into respective cylinder bore ensuring domed shaped boss on connecting rod faces towards
front of engine on RH bank of cylinders, and towards rear on LH bank of cylinders.

NOTE: When both connecting rods are fitted to each journal, bosses will face towards each other.

12. Pull connecting rod on to crankshaft journal.

CAUTION: Take care not to scratch crankshaft journals.

13. Fit big-end bearing caps and bearing shells.
14. Fit cylinder head(s).

FLYWHEEL

Flywheel- remove

1. Restrain crankshaft and remove 6 bolts securing flywheel.
2. Remove flywheel.

Inspect

1. Inspect flywheel face for cracks, scores and overheating. The flywheel can be refaced providing thickness does not go below minimum.
Flywheel minimum thickness A = 39.93 mm

2. Inspect ring gear for worn, chipped and broken teeth.

3. Renew ring gear if necessary.