TRUCK SERVICE MANUAL
ENGINE
[0.005 mm] above worn replacement limit listed in Table
Service Tools (Or Equivalent) Required
4-1. Use as a "No-Go" gauge in bore to check wear
ST-195
Plug Gauge
beyond replacement limits Check for out-of-round holes.
ST-249
Mandrel and Block
New dimensions on injector cam rollers are 0.503 to
3T-970
Plug Driving Mandrel
0.504 inch [12.78 to 12.80 mm]. Worn replacement limit
ST-1053
Plug Driving Mandrel
is 0.505 inch [12.83 mm]. On valve cam rollers new
dimensions are 0.5005 to 0.5015 inch [12.713 to 12.738
Standard Tools Obtain Locally
mm]. Worn replacement is 0.503 inch [12.78 mm]. If
Small Bore Gauge
rollers do not meet these specifications, mark for
Micrometer (o to 1 inch)
replacement.
Micrometer (1 to 2 inch)
Feeler Gauge (0.006 inch
[0.15 mm])
CAM FOLLOWERS
DISASSEMBLY AND INSPECTION
1. Remove lockscrews holding shafts in housing
and cup plug by using a sharp pointed chisel. Using
proper mandrel press both shafts out opposite end
forcing remaining cup plug out of hole. Mark or tag cam
follower levers for position before removal.
1. Bushing
4. Roller Pin
2. Lever
5. Roll Pin
2. Remove cam follower levers from housing.
3. Insert
6. Roller
Clean other parts in solvent.
Fig. 4-2 (N10412) Cam follower exploded view
3. Measure outside diameter of shafts with
micrometers. If worn smaller than 0.748 inch [19.0 mm]
11. Use micrometers to check outside diameter of
mark for replacement.
rollers. Injector cam roller new dimensions are 1.249 to
1.251 inch [31.72 to 31.78 mm]. Valve cam roller new
4. Check cam follower shafts around lockscrew
dimensions are 1.249 to 1.250 inch [31.72 to 31.75 mm].
end to make sure grooves are clean, inspect cam
Worn replacement limit for all rollers is 1.247 inch [31.67
follower housing for cracks or mating surface
mm].
imperfections. Discard unserviceable parts.
12. On all rollers the inside diameter must be
5. Check cam follower bushings for scratches,
concentric with the outside diameter within 0.002 inch
pitting or scoring. Check bushing inside diameter with
[0.05 mm]. Sides must be square to bore and parallel to
micrometers. If worn larger than 0.7515 inch [19.088
each other within 0.004 inch [0.10 mm]. Check cam
mm] mark for replacement.
roller pins. New dimensions are 0.4995 to 0.500 inch
6. Check for surface imperfections by magnetic
[12.69 to 12.70 mm]. If worn smaller than 0.497 inch
inspection. Apply coil magnetization, amperage at 300 to
[12.62 mm] mark for replacement. If rollers were scored
500 with residual Magnaglo.
or galled, make careful inspection of camshaft lobes for
damage.
7. Inspect edges of cup plug holes in cam follower
housing for sharp edges or nicks. If damaged, chamfer
entrance of hole to form a slight radius and break sharp
BUSHING INSTALLATION
edges to aid installation of cup plug.
1. If cam follower bushing is worn beyond limits,
remove bushing with ST-249 Mandrel and Block. Blow
8. Cam follower levers have a removable insert (3,
out oil passages with compressed air.
Fig. 4-2). These must be replaced if scored or extremely
worn. Check with a new push tube ball or 0.625 inch
2. Install new cam follower bushings using ST-249
[15.88 mm] checking ball and Prussian Blue. This area
Mandrel. Either one-piece or two-piece bushings may be
must "blue in" 80% blue or insert must be replaced.
used. When installing one-piece bushings, care must be
taken to align oil holes in bushing with holes in cam
9. Remove cam roll pins (5), roller pins (4) and
follower.
rollers (6) from cam follower levers (2).
10. Inspect cam rollers.
Set small bore gauge
Note: Do not use a two-piece bushing with levers that
0.0002 inch
are not welded closed at rear or loss of oil pressure will
occur.
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