TIMING CHAIN—MEASURING WEAR
NOTE: This procedure must be performed with the
timing chain cover removed.
(1) Remove the timing chain cover. Refer to Timing
Chain Cover in this section for procedure.
(2) To determine if the secondary timing chains
are worn, rotate the engine clockwise until maximum
tensioner piston extension is obtained. Measure the
distance between the secondary timing chain ten-
sioner housing and the step ledge on the piston (Fig.
17). The measurement at point (A) must be less than
15mm (.5906 inches).
(3) If the measurement exceeds the specification
the secondary timing chains are worn and require
replacement. Refer to Timing Chain and Sprockets in
this section for procedure.
PISTONS—FITTING
BORE GAGE METHOD
(1) To correctly select the proper size piston, a cyl-
inder bore gauge, capable of reading in 0.003 mm
(.0001 in.) INCREMENTS is required. If a bore
gauge is not available, do not use an inside microme-
ter.
(2) Measure the inside diameter of the cylinder
bore at a point 49.5 mm (1-15/16 inches) below top of
bore. Start perpendicular (across or at 90 degrees) to
the axis of the crankshaft at point A and then take
an additional bore reading 90 degrees to that at point
B (Fig. 19).
(3) The coated pistons will be serviced with the
piston pin and connecting rod pre-assembled. Tin
coated pistons should not be used as replacements for
coated pistons.
(4) The coating material is applied to the piston
after the final piston machining process. Measuring
the outside diameter of a coated piston will not pro-
vide accurate results (Fig. 18). Therefore measuring
the inside diameter of the cylinder bore with a dial
Bore Gauge is MANDATORY. To correctly select the
proper size piston, a cylinder bore gauge capable of
reading in 0.003 mm (.0001 in.) increments is
required.
(5) Piston installation into the cylinder bore
requires slightly more pressure than that required
for non-coated pistons. The bonded coating on the
piston will give the appearance of a line-to-line fit
with the cylinder bore.
Fig. 14 Camshaft Dowel To Sprocket Alignment
1 – ADJUSTABLE PLIERS
2 – CAMSHAFT DOWEL
Fig. 15 Camshaft Sprocket Installation—Left
Cylinder Head
1 – TORQUE WRENCH
2 – CAMSHAFT SPROCKET
3 – LEFT CYLINDER HEAD
4 – SPECIAL TOOL 6958 SPANNER WITH ADAPTER PINS 8346
9 - 22 4.7L ENGINE DN
SERVICE PROCEDURES (Continued)
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