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VALVE
SEATS
CAUTION: The 5.2L engine cylinder head combus-
tion chambers have been modified by valve shroud-
ing. DO NOT UNSHROUD VALVES DURING VALVE
SEAT REFACING (Fig. 15).
REFACING STONE f
MUST NOT CUT
VALVE SHROUD
Fig. 15 Refacing 5.2L Engine Valve Seats
(1) When refacing valve seats, i t is i m p o r t a n t t h a t
t h e correct size valve guide p i l o t be used for reseat-
i n g stones. A true and complete surface m u s t be ob-
t a i n e d .
(2) Measure the concentricity of valve seat using
d i a l indicator No. 13725. Total r u n o u t should not ex-
ceed 0.051 m m (0.002 inch) (total indicator reading).
(3) Inspect the valve seat w i t h Prussian blue to de-
t e r m i n e where the valve contacts t h e seat. To do
t h i s , coat valve seat L I G H T L Y w i t h Prussian blue
t h e n set valve i n place. Rotate t h e valve w i t h l i g h t
pressure. I f the blue is transferred to t h e center of
valve face, contact is satisfactory. I f the blue is trans-
ferred to top edge of valve face, lower valve seat w i t h
a 15° stone. I f the blue is transferred to bottom edge
of valve face raise valve seat w i t h a 60° stone.
(4) When seat is properly positioned t h e w i d t h of
i n t a k e seats should be 1.587 to 2.381 m m (1/16 to 3/
32 inches). The w i d t h of the exhaust seats should be
2.0 t o 2.5 m m (5/64 to 3/32 inches).
TESTING
VALVE
SPRINGS
(1) Whenever valves have been removed for inspec-
t i o n , reconditioning or replacement, valve springs
should be tested. As a n example t h e compression
l e n g t h of the spring to be tested is 1-5/16 inches.
T u r n table of Tool C-647 (Fig. 16) u n t i l surface is i n
l i n e w i t h the 1-5/16 i n c h m a r k o n the threaded stud
and t h e zero m a r k to t h e front. Place s p r i n g over
stud on t h e table and l i f t compressing lever to set
tone device. P u l l on torque wrench u n t i l p i n g is
heard. Take reading on torque wrench a t t h i s i n -
stant. M u l t i p l y this reading by two. This w i l l give
t h e spring load at test length. F r a c t i o n a l measure-
ments are indicated o n t h e table for f i n e r adjust-
ments. Refer t o specifications
t o o b t a i n
specified
h e i g h t a n d allowable tensions. Discard t h e springs
t h a t do not meet specifications.
RF259
Fig. 16 Testing Valve Spring with Tool C-647
(2) Inspect each valve s p r i n g for squareness w i t h a
steel square and surface plate, test springs f r o m both
ends (Fig. 17).
(3) I f the s p r i n g is more t h a n 1.984 m m (5/16 inch)
out o f square, i n s t a l l a new spring.
~
VALVE SPRING
SQUARE
RF180
Fig. 17 Checking
Valve Spring for
Squareness
INSTALLATION
I n s t a l l i n g t h e w r o n g e x h a u s t v a l v e s p r i n g i n
engines w i t h positive rotors c a n c a u s e severe e n -
gine damage. R e f e r to specifications for p r o p e r
identification.
(1) Coat valve stems w i t h l u b r i c a t i o n o i l and insert
t h e m i n cylinder head.
(2) I f valves or seats are reground, check valve
stem height w i t h Tool C-3968 (Fig. 18). I f valve is
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