IO-390-D Series Engine Maintenance Manual
© 2020 Avco Corporation. All Rights Reserved
72-20
March 2020
Page 177
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.
Figure 87
Torque Hold-Down Plates (ST-222)
CAUTION
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
(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.
