IO-390-D Series Engine Maintenance Manual
© 2020 Avco Corporation. All Rights Reserved
72-30
March 2020
Page 223
IO-390-D Series Engine Maintenance Manual
I.
Use the same sequence shown in Figure 29, complete a torque check to 50 ft.-lb. (68 Nm) for
all 1/2-in. nuts on the cylinder base studs.
J.
Tighten both ends of the free thru-studs at the same time at all locations. Make sure all thru-
studs have at least 1-1/2 threads above attaching nuts at both ends.
K.
Make sure all cylinder base hold-down nuts are torqued. Complete a torque check of all nuts
on the cylinder base using the torque wrench to apply the appropriate torque on each nut for 5
seconds. If the nut does not turn, it is correctly torqued.
L.
Apply torque seal to all cylinder hold-down nuts.
CAUTION
MAKE SURE ALL CYLINDER FASTENERS ON THE CRANKCASE
ARE TORQUED CORRECTLY AND NONE ARE LOOSE.
M.
Shroud Tube Installation
CAUTION
BE SURE THERE IS NO OIL INSIDE THE TAPPET BODIES AND THAT
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 ABSOLUTELY DRY FOR THE TAPPET
CLEARANCE CHECK.
NOTICE:
Install the upper and lower shroud tube seals (Figure 23) 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
corresponding cylinder.
(1)
For each of the two shroud tubes,
install the plunger assembly and
hydraulic socket in the tappet body in
the crankcase (Figure 30).
(2)
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.
(3)
Install new upper and lower shroud
tube seals into the cups in the tappet
bores of the crankcase (Figure 31)
and cylinder head.
(4)
On each shroud tube, assemble the
other shroud tube seal and sleeve
over the outer end of the shroud tube
(Figure 15).
Figure 30
Tappet Plunger and Socket
Figure 31
Shroud Tube Oil Seals in Crankcase
