Pontiac Fiero 1988 Service Manual page 281

6 A 4 GENERAL ENGINE MECHANICAL
n®1 Inspect
Valve stem tip for wear. The valve stem tip may
be reconditioned by grinding. If the valve has
rotators and the stem tip wear pattern indicates
rotator failure, or if the rotators bind or stick,
they must be replaced.
Proper Tip
Pattern
Rotator
Functioning
Properly
No Rotation
Pattern
Replace Rotator
and check rotation
Partial Rotation
Tip Pattern
Replace Rotator
and check rotation
G34171-6A-BG
Figure 5 Valve Stem Tip Wear
• Follow the grinder manufacturer's instructions.
Make sure the new surface is perpendicular to the
valve stem.
• Valve lock (keeper) and oil seal grooves for
chipped or worn lands. Replace the valve if
chipped or worn.
m Valve face for burning or cracking. If pieces are
broken off, inspect the corresponding piston and
cylinder head area for damage.
• Valve stem for burrs and scratches. Burrs and
m i n o r
scratches may be removed with an oil
stone.
• Valve stem for straightness and valve head for
bending or distortion. Use "V" blocks. Bent or
distorted valves must be replaced.
• Valve face for grooving. If the groove is so deep
that refacing would result in a knife edge
(destroying the margin), the valve must be
replaced.
• The valve face may be reground to specifications,
if it is otherwise in good condition. If the valve
face cannot be ground within the limits given, it
must be replaced.
• Measure valve margin after grinding valves. If the
margin is less than the minimum recommended
margin, replace the valve.
N O T I C E :
New valves must not be lapped.
Lapping destroys the protective coating on the
valve face.
V A L V E SPRINGS
]9
Inspect
m Valve springs
Expanded height
Spring ends. If they are not parallel, the
spring is bent and must be replaced.
m
NEW V A L V E
WORN V A L V E
1 — V A L V E TIP
2— KEEPER GROOVE
3 — STEM-LEAST WORN
SECTION
4-STEM-MOST WORN
SECTION
i—FACE
6—MARGIN
G20007-6A
Figure 6 Valve Wear
Valve spring seating surface of the valve rotators,
or spring retainers, for wear or gouging. Replace
as required.
NOT MORE THAN 1/16
1
VARIANCE WHIlf
ROTATING SPRING
G34161-6A-BG
Figure 7 Checking Valve Springs
V A L V E S E A L S
Important
If seals are the
U m b r e l l a t y p e ,
push them
down as far as they will go. If oversized
valves have been installed, oversized valve
stem seals must be used. Intake and exhaust
valve stem seals may be different.