REPAIR INSTRUCTIONS, PART 1
Page 263
Inspection
A. Perform a general inspection of all
components of the rocker arm shaft and
bracket assembly for evidence of damage or
wear. Replace components as necessary.
B. If loose or broken rocker arm shaft mounting
bolts are encountered at disassembly, or if
the rocker shaft is bent, contingent damage
must be inspected for and repaired as
follows:
앫 Inspect the bottom surfaces of the
rocker shaft mounting brackets for
signs of fretting damage. Mounting
brackets can be reused if only slight
signs of fretting and/or polishing are
evident, as long as there are no other
types of damage which could render
the rocker shaft assembly unusable.
Replace the mounting brackets if
fretting damage is severe enough that a
wear step of approximately 0.002"
(0.508 mm) is seen. A 0.002"
(0.508 mm) wear step can be felt by
dragging your fingernail across the
step.
292
Figure 292 — Rocker Shaft Mounting Bracket Showing
Signs of Fretting Damage
On engines where the rocker shaft mounting
bolts have come loose or have broken on one
cylinder head only, the rocker shaft on the other
cylinder head must also be removed, and the
mounting brackets and the mating surfaces on
the cylinder head inspected for fretting damage.
Replace the brackets and cylinder head as
required.
앫 Inspect the mating surface on the
cylinder head at the locations where
fretting damage was found on the
corresponding rocker shaft mounting
bracket. If fretting damage on the
cylinder head is severe (where the
machined surface is severely pitted and
a step of approximately 0.002"
[0.508 mm] is evident), the cylinder
head must be replaced.
293
Figure 293 — Severe Fretting Damage on Cylinder Head
Rocker Arm Bracket Mounting Surface
A wear step of 0.002" (0.508 mm) on
the cylinder head mating surface can
be determined by laying a straightedge
across the rocker shaft mounting
bracket mating surface. If a 0.002"
(0.508 mm) thickness gauge can be
slid under the straightedge, or if light
can be seen under the straightedge in
the area of the fretting damage, the
damage is severe enough to warrant
replacement of the head.
1. Severe Fretting
2. Wear Step
3. Machined Surface
1. Wear Step 2. Severe Fretting
5-111.bk Page 263 Monday, July 10, 2006 2:26 PM
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