Engine Overhaul Manual v8 4.0 4.6
ENGINE
OVERHAUL
33
Piston rings - inspection
1. Temporarily fit new compression rings to
piston.
NOTE: If replacement pistons are to be
fitted, ensure rings are correct for piston.
The 2nd compression ring marked ’TOP’ must be
fitted, with marking uppermost, into second
groove. The 1st compression ring fits into top
groove and can be fitted either way round.
2. Check compression ring to groove clearance:
1st compression ring A = 0.05 to 0.10 mm
(0.002 to 0.004 in).
2nd compression ring B = 0.05 to 0.10 mm
(0.002 to 0.004 in).
3. Insert piston ring into its relevant cylinder bore,
held square to bore with piston and check ring
gaps.
1st compression ring = 0.30 to 0.50 mm (0.012
to 0.02 in)
2nd compression ring = 0.40 to 0.65 mm
(0.016 to 0.03 in)
Oil control ring rails = 0.38 to 1.40 mm (0.014
to 0.05 in)
4. Retain rings with their respective pistons.
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 remover/replacer adapter
LRT-12-126/2 with its long spigot inside bore
of hexagon body.
5. Locate piston and connecting rod assembly on
centre screw and up to adapter LRT-12-126/2
ensuring that prongs of adapter are positioned
on piston either side of gudgeon pin.
6. Fit remover/replacer bush LRT-12-126/1 on
centre screw with flanged end away from
gudgeon pin.
7. Screw stop nut on to centre screw.
CAUTION: Ensure that LRT-12-126/1 is
correctly located in gudgeon pin bore of
piston.
8. Lock the stop nut securely with the lockscrew.
9. Push connecting rod to right to locate end of
gudgeon pin in adapter LRT-12-126/2.
10. Ensure that LRT-12-126/1 is still located in
gudgeon pin bore of piston.
11. Screw large nut up to LRT-12-013 .
12. Hold lockscrew and turn large nut until
gudgeon pin is withdrawn from piston.
CAUTION: Ensure that prongs of adapter
LRT-12-126/2 remain in contact with piston
and do not contact gudgeon pin.