Camshaft - GMC 1989 Light Duty Truck Repair Manual

6A4-16 4.8 LITER L6
A. In d ic a to r
B. C h e c k in g F ix tu re
182. C a m sh a ft
Figure 26— Measuring Camshaft Journal Runout
*
A ssem ble (Figure 4)
1
. Gasket (36) to the exhaust manifold (37).
2. Intake manifold (31) and exhaust manifold (37).
3. Nuts (32), bolts (39) and washers (40). Leave the
fasteners hand-tight until the manifold to cylinder
head bolts are torqued. R efer to " Intake and
Exhaust Manifold Installation."

CAMSHAFT

Im portant
• Whenever the camshaft needs to be replaced, a
new set of hydraulic lifters must also be installed.
Inspect (Figures 5, 26, 27, and 28)
— Camshaft (182) lobes and journals for scratches,
pitting, scoring, and wear.
— Timing gear (94) for damaged or missing teeth.
M easure (Figures 26, 27, and 28)
Tool Required:
J-7872 Dial Indicator (or equivalent)
Figure 2 7 — C hecking th e C am shaft Journals
B-04578
Figure 28— Measuring Camshaft Thrust Plate
— C am shaft (182) runout (figure 26). M ount the
camshaft between centers or in V-blocks. Using
J-7872 (or equ iva len t), ch eck the interm e dia te
camshaft journals. If runout exceeds 0.020-inch, the
c a m s h a ft is e xce ss iv e ly b ent and s h ou ld be
replaced, along with the camshaft bearings.
— Camshaft journal out of round. Use a micrometer
(fig u re
1.8677-1.8697-inch.
— Thrust plate (94) to camshaft (182) clearance. This
clearance governs camshaft end play. Use a feeler
g a g e
0.003-0.008-inch. Excessive clearance indicates that
the thrust plate is worn and should be replaced, as
outlined following:
CAMSHAFT GEAR AND
THRUST PLATE REPLACEMENT
❖
D isassem ble (Figures 5 and 29)
1. Camshaft gear (94).
Figure 2 9 — R em oving th e C am shaft G ear
Clearance (Camshaft End Play)
2 7). T h e p ro p e r
(fig u re 28). P ro p e r
d ia m e te r is
c le a ra n c e is