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9-34
ENGlN ES-8-CYLINDER
Bc(
INTAKE
VALVE
\
FACE'
*------
STEM
-
VALVE SPRING RETAINER
HAUST
ALVE
t
I
-.
K
H330C
w
Fig. 75-Intake
and Exhaust Valve Faces
take valves and .018 inch on exhaust valves for 273,
318,361,383, and 426 Cubic Inch Engines.
(6) If the tolerance is excessive, ream guides and
install valve with oversize stems. Reamer Tool C-3433
will ream guides for .005 inch oversize valve stems.
Tool C-3430 for .015 inch oversize, Tool (2-3427 for
.030 inch oversize. Turn reamer by hand, and clean
guides thoroughly when finished. Use .005 inch ream-
er first and,
if
necessary, the .015 inch, then the .030
inch so the guides remain true in relation to the seat.
Refacing Valves and Valve Seats
The intake and exhaust valve faces have a 45"
angle. Always inspect the remaining margin after the
valves are refaced (Fig. 75). Valves with less than
:{IG4
inch margin should be replaced.
(1) The angle of both valve and seat should be iden-
tical. When refacing the valve seats it is important
that the correct size valve guide pilot be used for the
reseating stones. A true and complete surface must be
obtained.
(2) Measure the concentricity of the valve seat us-
ing dial indicator No. 13725. The total runout should
not exceed .003 inch (total indicator reading).
(3) Inspect the valve seat with Prussian Blue to de-
termine where the valve contacts the seat. To do this,
coat the valve seat
lightly
with Prussian Blue then set
the valve in place. Rotate the valve with light pres-
sure. If the blue is transferred to the center of the
valve face, the contact is satisfactory.
If
the blue
is
transferred to the top edge of the valve face, lower the
valve seat with a 30" stone. If the blue
is
transferred
to the bottom edge of the valve face raise the valve
seat with a 60" stone.
(4) When the seat is properly positioned the width
of the intake seats should be
to
inch. The width
of the exhaust seats should be
3/ln4
to
*Il6
inch.
VALVE
TOOL
Fig. 76-Measuring Valve Stem length ITypicalJ
(5) When the valves and seats are reground, the
position of the valve in the cylinder head is changed,
the valve stems will extend farther out of the cylin-
der heads. This increased dimension will decrease
valve spring compression, and for 361, 383, and 426
cubic inch engines only
it
will shorten the operating
length of the hydraulic tappet. This means that the
plunger is operating closer to its bottomed position,
with less clearance available for thermal expansion
of the valve mechanism during high speed driving.
(6) The design of the valve mechanism includes a
safety factor to allow for a limited amount of wear,
and the refacing of valves and seats.
(7) To insure that the limits have not been
ex-
ceeded, the dimension from valve spring seat in head
to
valve tip should be measured with gauge Tool
C-3968 for 273 Cubic Inch Engine and gauge Tool
C-3927 for 318 Cubic Inch Engine and gauge Tool
C-3648 for 361, 383 and 426 Cubic Inch Engines, as
shown in Figure 76.
If the valve stem extends above the gauge, grind
the end of the stem to fall between the maximum
and the minimum.
Testing Valve Springs
(1) Whenever the valves have been removed for in-
spection, reconditioning or replacement, the valve
springs should be tested. To test a spring, determine
the length at which the spring is to be tested. As an
example, the compressed length of the spring to be
tested is ll.?/:<?
inches. Turn the table of Tool C-647
until surface is in line with the 115/lja inch mark on the
threaded stud and the zero mark to the front. Place
spring over the stud on the table and lift the compress-
ing lever to set the tone device. Pull on torque wrench
until a ping is heard. Take the reading on torque
wrench at this instant. Multiply this reading by two.
This will give the spring load at the test length.
Fractional measurements are indicated on the table
for finer adjustments. The valve springs should
test
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