Discovery II (LT) V8-4.6L (2003)
/v8-4.6l/Page-360002.png)
1. Clean carbon from piston. Inspect piston for distortion, cracks and burning.
2. Remove piston rings from piston,
3. Measure and record piston diameter at 90° to gudgeon pin axis and 10 mm (0.4 in) from bottom of the skirt. The piston must be 0.02 to 0.045 mm
(0.001 to 0.002 in) smaller than the cylinder bore.
4. Check gudgeon pin bore in piston for signs of wear and overheating.
5. Pistons fitted on production are graded 'A' or 'B', the grade letter is stamped on the piston crown.
^
Piston diameter: Grade 'A' = 93.970 to 93.985 mm (3.6996 to 3.7002 in).
^
Piston diameter: Grade 'B' = 93.986 to 94.00 mm (3.7002 to 3.7007 in).
6. Worn cylinders fitted with grade 'A' pistons may be honed to accept the grade 'B' piston provided that specified cylinder bore and ovality limits are
maintained. Grade 'B' pistons are supplied as service replacements. Do not attempt to de-glaze cylinder bores.
7. Check gudgeon pins for signs of wear and overheating.
8. Check clearance of gudgeon pin in piston.0 Gudgeon pin to piston clearance = 0.006 to 0.015 mm (0.0002 to 0.0006 in).
9. Check overall dimensions of gudgeon pin. Gudgeon pins are only supplied as an assembly with replacement pistons.
^
Gudgeon pin length = 60.00 to 60.50 mm (2.362 to 2.382 in).
^
Gudgeon pin diameter = 23.995 to 24.00 mm (0.9446 to 0.9448 in).
10. Measure cylinder bore wear and ovality in two axis 40 to 50 mm (11.6 to 2 in) from top of bore. The temperature of piston and cylinder block
must be the same to ensure accurate measurement. Do not attempt to de-glaze cylinder bores.
^
Grade 'A' pistons: Cylinder bore = 94.00 to94.015 mm (3.7007 to 3.7013 in).
^
Grade 'B' pistons: Cylinder bore= 94.016 to 94.030 mm (3.7014 to 3.7019 in).
^
Maximum ovality= 0.013 mm (0.0005 in).
11. Check alignment of connecting rods.
Reassembly
1. Pistons have a 5 mm (0.2 in) offset gudgeon pin which can be identified by an arrow mark on the piston crown. This arrow must always point
towards the front of the engine.
