Inspecting Pistons in Engine Overhaul Manual v8 40 46
ENGINE
34
OVERHAUL
13. Dismantle tool LRT-12-013 and remove piston,
connecting rod and gudgeon pin.
NOTE: Keep each piston and gudgeon pin
with their respective connecting rod.
14. Repeat above operations for remaining
pistons.
Pistons - inspection
1. Clean carbon from pistons.
2. Inspect pistons for distortion, cracks and
burning.
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: DO NOT attempt to de-glaze
cylinder bores.
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)