Pontiac FIREBIRD 1972 Service Manual page 583

V-8 ENGINE 6-7 1
Valves should be ground on a special bench grinder de-
VALVE KEYS-@
VALVE
ROTATOR
!
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/
I
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-ROCKER
VALVE ARMS
SPRING
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F i g . 6 - 1 1 7 V a l v e C o m p o n e n t s
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307 Engine
Run engine at approximately 1500 RPM. There should
appear to be motion between the body and the collar. The
body will appear to "walk" around the collar. Rotator
action can be either clockwise or counterclockwise. In
some instances, the direction of rotation will change upon
removal and reinstallation. This does not matter so long
as it rotates.
In addition, anytime the valves are removed the tips of the
valve stem should be inspected for improper pattern,
which could indicate valve rotator malfunction (Fig. 6-
118).
VALVES AND SEATS
RECONDITION
1. Reface valves and seats as follows:
PROPER TIP NO ROTATION PARTIAL ROTATION
PATTERN PATTERN TIP PATTERN
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ROTATOR REPLACE ROTATOR REPLACE ROTATOR
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FUNCTIONING AND CHECK ROTATION AND CHECK ROTATION
PROPERLY
signed specifically for this purpose and built by a
reputable manufacturer. Valve seats should be
ground with reputable power grinding equipment
having stones ofthe correct seat angle and a suitable
pilot which pilots in the valve stem guide. To ensure
positive sealing of the valve face to its seat, the grind-
ing stones should be carefully refaced before any
grinding is done. Intake valve seat angle is 30" on all
except 307 engines, 46" on 307 engines and exhaust
valve seat angle is 45" on all cylinder heads. Intake
valve face angle is 29" on all except 307 engine, 45" on
307 valves and exhaust valve face angle is 44" on all
valves except 307, which is 45". This will provide
hairline contact between valve and seat to hovide
positive sealing and reduce build-up of deposits on
seating surfaces (Fig. 6-1 19).
DO NOT USE R E F A ~ I N G EQUIPMENT EXCES-
SIVELY; only enough material should be removed to true
up surfaces and remove pits. The valve head will run
hotter as its thickness is diminished; therefore, if the valve
face cannot be cleaned up without grinding to a point
where the outside diameter of the valve has a sharp edge,
the valve should be replaced. Whenever it is necessary to
replace a valve, the new valve should be of the same stem
diameter as the valve removed (unless the valve guide is
reamed to provide proper fit).
Width of exhaust valve seats should be 1/16" (.048"-
.070"). Intake valve seat should be between 3/64" and
1/16" (.045"-.07 1
").
If seat width is excessive, it should
be
narrowed by grinding with a flat stone (Fig. 6-120). This
is the only method that should be used to narrow the seat.
Lapping of valve seats is not required nor recommended.
2. Concentricity of valve seat and valve guide can be
checked by using a suitable dial indicator or prussian
blue. When using a dial indicator, total runout should
not exceed .002".
When prussian blue is used, a light coat should be
applied to the face of the valve only and the valve
A-SEAT WIDTH
B-FACE ANGLE
C-SEAT ANGLE
A
D-VALVE FACE C
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Fig.
6 - 1
18 Valve Stem
W e a r P a t t e r n s
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307
E n g i n e
F i g . 6 - 1 1 9
Valve
S e a t
and Face
A n g l e s