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(5) Install the shroud tube spring and
washer over the inner ends of each
shroud tube where the detent notches
in the spring are 90 removed from
the tangs on the shroud tubes as
shown in Figure 32.
(6) Install each shroud tube through the
shroud tube seal in the crankcase.
(7) Hold both shroud tubes with the
detent at the inner end at the unlocked
position and insert the outer end of
the tubes in the rocker box of the
cylinder head.
(8) Make sure that all shroud tube seals
are installed squarely.
(9) Turn each shroud tube 90 and use
either a shroud tube wrench, ST-142
(Figure 33) or an internal pipe
wrench to engage the tangs with the
detents in the springs to lock each
shroud tube in position.
(10) As necessary, gently tap the shroud
tube springs with a rubber mallet to
correctly and securely seat these
springs (Figure 34).
N. Push Rod Installation
(1) Make sure that the valves on the applicable cylinder are closed on the top dead center of
the compression stroke.
(2) Install the valve stem cap over the exhaust valve stem (Figure 23).
(3) Install the push rods into the full length of the shroud tube.
(4) Press the push rods tightly from the outer end of the shroud tube to test the spring tension
and free travel of the unloaded or dry hydraulic tappet plungers. Make sure the springs
compress and return.
CAUTION
O. Install the rockers with the cupped end on the push rod.
P. Align each valve rocker assembly (including the washer and bushing) with the rocker shaft.
Q. Slide the rocker shafts through each valve rocker assembly (Figure 23) to seat the valve
rocker in place for both the intake and exhaust valves.
R. Make sure the valve rocker assemblies are in the correct position on the intake and exhaust
valves.
72-30
Page 224
EXHAUST AND INTAKE ROCKER ASSEMBLIES ARE
DIFFERENT. MAKE SURE THAT THE ROCKERS ARE
CORRECTLY ASSEMBLED AND INSTALLED ON THE CORRECT
SIDE (INTAKE OR EXHAUST) OF THE CYLINDER.
IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
Figure 32
Shroud Tube with Springs and Washer
Figure 33
Shroud Tube Wrench ST-142
Figure 34
Correctly Aligned Shroud Tube Springs
© 2020 Avco Corporation. All Rights Reserved
March 2020
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