Lycoming YO-233-B2A Maintenance Manual page 157

YO-233-B2A Engine Maintenance Manual
TEO-540-A1A Engine Maintenance Manual
H. Shroud Tube Installation
CAUTION BE SURE THERE IS NO OIL INSIDE THE TAPPET BODIES AND THAT
NOTICE: Install the lower shroud tube seals (Figure 15) in the crankcase first.
One shroud tube installs on the exhaust port of the cylinder and another shroud tube
installs on the intake port.
The tappet plunger must be the one for the applicable tappet socket on the applicable
cylinder.
(1) For each of the two shroud tubes, install the
plunger assembly and hydraulic socket in the
tappet bore in the crankcase (Figure 41).
(2) Rotate the crankshaft to move both installed
plunger assemblies and hydraulic sockets to
their lowest position in the tappet bores in the
crankcase.
(3) Apply engine oil mixture (15% pre-lubricant
(STP or equivalent) and 85% SAE No. 50
mineral base aviation grade lubricating oil) to
all four of the shroud tube seals, two for each
shroud tube.
(4) Install one shroud tube seal and the washer
into the cups in the tappet bores of the
crankcase (Figures 42 and 43).
(5) On each shroud tube, assemble the other
shroud tube seal over the outer end of the
shroud tube (Figure 43).
(6) Insert each shroud tube through the hole in
the rocker box and seat the end firmly into the
crankcase.
(7) Install the shroud tube spring, new lockplate,
and nut (Figure 44). Torque the nut to 96 in.-
lb. (11 Nm).
NOTICE: If necessary, turn the nut up to one
additional hex to align the flat on the nut with the
tab on the lockplate. Lockplate tabs must not be
bent up on the corner of the nut.
(8) Ensure the flat on the nut aligns with the
lockplate tab and bend the tab up.
© 2021 Avco Corporation. All Rights Reserved
February 2021
THE PLUNGER ASSEMBLY AND CYLINDER ASSEMBLY ARE
THOROUGHLY CLEAN AND DRY. WASH ANY LUBRICATING OR
PRESERVATIVE OIL (MINERAL SPIRITS, STODDARD SOLUTION, OR
EQUIVALENT) FROM THESE PARTS, SINCE PLUNGER ASSEMBLIES
MUST BE COMPLETELY DRY FOR THE TAPPET CLEARANCE CHECK.
Figure 41
Tappet Plunger and Socket
Figure 42
Shroud Tube Oil Seals in Crankcase
Figure 43
Insert the Shroud Tube
Figure 44
Shroud Tube Spring, Lockplate, and Nut
72-30
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