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IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
(11) Install the Torque Hold-Down Plate (ST-
222, Figure 87) or equivalent on the
cylinder pads over the thru-studs.
(12) Attach the plates with washers and nuts on
the thru-studs. Tighten the nuts only finger
tight at this time.
(13) Make sure that the plates remain parallel
with the cylinder decks of the crankcase.
NOTICE: Before tightening the thru-studs,
make sure that they extend equally
for both sides of the crankcase.
CAUTION
(14) Install a nut (and spacer as required) on each thru-stud at the mating flanges on the
crankcase halves in the sequence shown in Figure 88 to attach the crankcase halves
securely.
NOTICE: To ensure uniform loading on the main bearings, immediately torque the nuts on
the anchored thru-studs and the free thru-studs in sequence (Figure 88),
beginning at the center of the crankcase and then progressing alternately to the
rear and front of the engine.
© 2020 Avco Corporation. All Rights Reserved
March 2020
TO ENSURE CORRECT ASSEMBLY OF THE CRANKCASE
HALVES, TO MINIMIZE THE POSSIBILITY OF THE SUBSEQUENT
LOOSENING OF CYLINDER BASE NUTS, AND TO ENSURE A
UNIFORM LOAD ON THE MAIN BEARINGS IN THE CRANKCASE,
FOLLOW THE STEPS IN THE TORQUE SEQUENCE IN THE
ORDER GIVEN IN FIGURE 88.
Figure 88
Crankcase Tightening Sequence
Figure 87
Torque Hold-Down Plates (ST-222)
72-20
Page 177
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