GMC 1982 Light Duty Truck, Руководство по обслуживанию

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M ARK IV 6A5-11
V A LV E M E C H A N IS M
Removal
1. Remove rocker arm covers as previously outlined.
2. Remove rocker arm nuts, rocker arm balls, rocker arms
and push rods. Place rocker arms, rocker arm balls and
push rods in a rack so they may be reinstalled in the
same locations.
In s ta lla tio n a n d A d ju s tm e n t
Whenever new rocker arms an d /o r rocker arm balls are
being installed, coat bearing surfaces of rocker arm s and
rocker arm balls with " Molykote " or its equivalent.
1. Install push rods. Be sure push rods seat in lifter socket.
2. Install rocker arms, rocker arm balls and rocker arm
nuts. T ighten rocker a rm nuts until all lash is
eliminated.
3. Adjust valves when lifter is on base circle of camshaft
lobe as follows:
a. C rank engine until m ark on torsional dam per lines
up with center or " O " m ark on the timing tab
fastened to the crankcase front cover and the engine
is in the # 1 firing position. This may be determined
by placing fingers on the # 1 valve as the m ark on the
dam per comes near the " O " m ark on the crankcase
front cover. If the valves are not moving, the engine is
in the # 1 firing position. If the valves move as the
m ark comes up to the timing tab, the engine is in # 6
firing position and should be turned over one more
time to reach the # 1 position.
b. W ith the engine in the # 1 firing position as deter­
mined above, the following valves may be adjusted.
- Exhaust--1, 3,4, 8
-- Intake--1,2, 5, 7
c. Back out adjusting nut until lash is felt at the push
rod then turn in a d ju stin g nut until all lash is
removed. This can be determined by rotating push
rod while turning adjusting nut (fig. 6 A 5 - 11). When
play has been removed, turn adjusting nut in one full
additional turn (to center lifter plunger),
d. C rank the engine one revolution until the po in ter"o "
m a rk and torsional d a m p e r m a rk are again in
alignm ent. This is # 6 firing position. W ith the
engine in this position the following valves may be
adjusted.
— E x h a u s t- 2 , 5, 6, 7
— I n t a k e - 3 , 4, 6, 8
4. Install rocker arm covers as previously outlined.
5. S tart engine and adjust carburetor idle speed.
V A L V E STEM OIL SEAL a n d /o r V A LV E SPRING
Removal
1. Remove rocker arm cover as previously outlined.
2. Remove spark plug, rocker arm and push rod on the
cylinder(s) to be serviced.
3. Install air line adapter Tool J-23590 to spark plug port
and apply compressed air to hold the valves in place.
4. Using Tool J-5892 to compress the valve spring, remove
the valve locks, valve cap and valve spring and dam per
(fig. 6A5-12).
5. Remove the valve stem oil seal.
In sta lla tio n
1. Install new valve stem oil seal (coated with oil) in
position over valve guide (fig. 6A5-13). Seal installa­
tion instructions are supplied with each service kit.
Install seal following procedures outlined on the sup­
plied instruction sheet.
Fig. 6 A 5 -1 1--Valve Adjustm ent Fig. 6A5-12--Com pressing Valve Spring
2 3 5 9 0
W * ' ¥
J -5 8 9 2