GMC 1989 Light Duty Truck, Repair Manual, Page: 506 / 998

6A5-16 V8 ENGINE
Figure 28— Checking Alignment of Manifold Flanges
(Typical)
Im portant
E a ch c o n n e c tin g rod a n d b e a rin g ca p
should be m arked, beginning at the fron t of
the engine. C ylinders 1, 3, 5 and 7 are the
left bank and 2, 4, 6, and 8 are the right
bank. The num bers on the co nn ectin g rod
and bearing cap m ust be on the sam e side
w hen installed in the cylind er bore. If a
co nn ectin g rod is ever transposed from one
block or cylind er to another, new co nnecting
rod b e a rin g s s h o u ld be fitte d a n d th e
c o n n e c tin g rod s h o u ld be n u m b e re d to
co rresp on d w ith the new cylind er number.
M easure
• Ring end gap and ring clearance.
I f
Inspect
• Ring fit.
INTAKE AND EXHAUST
MANIFOLD
a y
Clean
— Old pieces of gasket from the gasket surfaces.
— E x c e s s iv e c a rb o n b u ild - u p in th e e x h a u s t
passages of the intake m anifold.
— Scale and deposits from the coolant passages of
the intake m anifold.
— EG R p a s s a g e (if used) o f e xc e s s iv e ca rb o n
deposits.
I f Inspect (Fig ure 28)
— M anifolds for cracks, broken flanges, and gasket
surface dam age.
— A lign m en t of exhaust m anifold flanges. Use a
straig ht edge and feeler gage (figure 28). If the
fla ng es do not align, the m anifold is w arped and
should be replaced.
Figure 29— Measuring Camshaft Run-Out
— AIR in je c tio n tu b e s fo r d a m a g e . R e p la ce as
needed.
CAMSHAFT
Im portant
• W henever th e ca m sh aft needs to be replaced, a
new set of valve lifters m ust also be installed.
I?
Inspect
C a m s h a ft lo b e s and jo u rn a ls fo r s c ra tc h e s ,
p itting, scoring, and wear.
M easure (Figures 29 and 30)
Tool R equired:
J 7872 Dial Indicator (or equivalent)
Camshaft runout (figure 29). Mount the camshaft in
V-blocks or between centers. Using J 7872, check
the intermediate camshaft journal. If runout exceeds
(0.0015-inch), the camshaft is excessively bent and
s h o u ld be rep la ce d a lo ng w ith th e c a m s h a ft
bearings.
Camshaft journal out-of-round. Use a micrometer
(figure 30). If the journals are more than 0.001-inch
out-of-round, replace the camshaft.