Discovery I (LJ) V8-4.0L (1996)
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3. Measure and record piston diameter at 90 ° to gudgeon pin axis and 10 mm (0.4 in) from bottom of skirt.
4. Check gudgeon pin bore in piston for signs of wear and overheating.
NOTE: Pistons fitted on production are graded 'A' or 'B', the grade letter is stamped on the piston crown.
Production piston diameter:
Grade A = 93.970 to 93.985 mm (3.700 to 3.7002 in)
Grade B = 93.986 to 94.00 mm (3.7003 to 3.701 in)
Grade B pistons are supplied as service replacements. Worn cylinder liners fitted with grade 'A' pistons may be honed to accept grade 'B' pistons
provided that specified cylinder bore and ovality limits are maintained.
CAUTION: Ensure replacement pistons are correct for the compression ratio of the engine. The compression ratio will be found on the
cylinder block above the engine serial number. Ensure that replacement connecting rods are correct length for engine being overhauled.
Connecting rod length between centres:
4.0 litre = 155.12 to 155.22 mm (6.10 to 6.11 in)
4.6 litre = 149.68 to 149.78 mm (5.89 to 5.91 in)
Gudgeon pins - inspection
NOTE: Gudgeon pins are only supplied as an assembly with replacement pistons.
1. Check gudgeon pins for signs of wear and overheating.
2. Check clearance of gudgeon pin in piston.
Gudgeon pin to piston clearance = 0.006 to 0.015 mm (0.0002 to 0.0006 in).
3. Check overall dimensions of gudgeon pin.
Overall length = 60.00 to 60.50 mm (2.35 to 2.4 in).
Diameter - measured at each end and centre of pin = 23.995 to 24.00 mm (0.94 to 0.95 in).
Cylinder liner bore - inspection
1. Measure cylinder liner bore wear and ovality in two axis 40 to 50 mm (1.5 to 1.9 in) from top of bore.
Cylinder liner bore:
Grade A piston fitted = 94.00 to 94.015 mm (3.700 to 3.701 in)
Grade B piston fitted = 94.016 to 94.030 mm (3.7014 to 3.702 in)
Maximum ovality = 0.013 mm (0.0005 in)
Cylinder liners having grade 'A' pistons fitted may be honed to accept grade 'B' pistons provided specified wear and ovality limits are maintained.
CAUTION: The temperature of piston and cylinder block must be the same to ensure accurate measurement.
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. Ensure all traces of grit
are removed after above operation.
