Pontiac Fiero 1988 Service Manual page 279

6A-2 GENERAL ENGINE MECHANICAL
I f| Important
# Any bolts that are suspected to be damaged
must be replaced.
2. Cylinder head for cracks, especially between
valve seats, and in the exhaust ports
3. Cylinder head deck for corrosion, sand inclusions
and blow holes.
• Do not attempt to weld the cylinder head,
replace it.
4. Cylinder head deck, intake and exhaust manifold
mating surfaces for flatness (Figure 2). These
surfaces may be reconditioned by parallel
grinding. If more than .39 mm (.010") V6, or .152
mm (.006") V8 must be removed, replace the
head.
1—FEELER GAGE 2-STRAIGHT EDGE
• o r ?
%
Q
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1
G20005-6A
Figure 2 Checking Cylinder Head Flatness
5. All threaded holes for damage. Threads may be
reconditioned with thread inserts (refer to Thread
Repair).
6. Seating surfaces
• Water jacket plugs
7. Valve guides for wear.
• Since the valve guide serves to support and
center the valve grinder, the valve guide
must be serviced before reconditioning the
valve seats. The valve guide must be cleaned
properly before any measuring or servicing
takes place. If the valve guide requires
reaming, this must be done first.
8. Valve seats for excessive wear and burned spots.
• Valve seats may be reconditioned by
grinding. An oscillating type valve seat
grinder is preferred. Follow the grinder
manufacturer's instructions. Refer to
Figure 3 for seat angles. If, after grinding,
the new seat is too wide, it may be narrowed
by using a 20° or 70° stone. The 20° stone will
lower the seat and the 70° stone will raise the
seat. If the seats are reconditioned, the
valves also must be reconditioned or
replaced.
1.
Assemble
Tool Required:
J 22677 Installer
Oil gallery and cooling jacket plugs. Coat plugs
with GM 1050026 sealer, or equivalent.
2. Spark plugs.
3. Valve and spring mechanism (refer to specific
engine section).
N O T I C E :
To avoid damage, install spark plugs
after cylinder head has been reinstalled.
V A L V E D I S A S S E M B L Y
Disassemble
® Valve and spring mechanism (refer to Specific
Engine Section)
Important
Be sure that valve train components are
kept together and identified so that they can
be reinstalled in their original location and
with the same mating surfaces as when
removed.
9
N O T I C E :
Avoid breaking the valve guide. If the
valve stem has mushroomed due to rocker arm
wear, remove burrs by chamfering the valve stem
with an oil stone or file. Do not remove the valve
from the guide using a hammer and drift punch.
Clean
Valves of carbon, oil and varnish. Carbon can be
removed with a wire brush, varnish by soaking in
carburetor cleaning fluid.
C A U T I O N : S a f e t y g l a s s e s m u s t b e
w o r n w h e n u s i n g a p o w e r w i r e b r u s h .
A v o i d i n h a l i n g of f u m e s a n d e x p o s u r e
o f s k i n t o c a r b u r e t o r c l e a n i n g f l u i d ,
a s
b o d i l y i n j u r y m a y r e s u l t .
m Do not scratch the valve stem with the wire
brush.
V A L V E GUIDES
Measure
Valve guide clearance
Insert the valve into its guide. Lift it 3mm
(1/8") off the seat and move it side to side,
measuring the amount of movement with a
dial indicator, or
With a hole gage, measure the valve guide
I.D. and measure the valve stem with a
micrometer and compare the clearance.
Refer to specific engine section for allowable
clearances.
The valve guides may be reamed oversize and an
oversized valve installed (Figure 4).
Reaming Valve Guides