B-2
IO-240 Series Engine Installation & Operation Manual
31 October 2011
Torque Specifications
•
If a nut slot cannot be aligned with a cotter pin hole within the specified limits,
substitute another serviceable nut to attain alignment.
•
If the cotter pin hole in a stud lies beyond the nut slots, when the nut has been torqued
properly, check the stud for proper installation or for backing out.
•
Check studs for necking.
•
Check the part for reduced thickness resulting from wear or incorrect part.
B-2. Cylinder Torque Procedure
Proper cylinder installation requires the bolts be torqued in multiple stages. Cylinder base
stud threads, through bolt threads and nuts must be lubricated with clean 50-weight
aviation oil. Through bolt nuts at cadmium plated washers require a lower torque value to
achieve the same through-bolt pre-load since the lubricity of the cadmium plating reduces
joint friction.
1. Torque cylinder base nuts to ½ of the specified torque value for the fastener.
2. Torque the cylinder through bolt nuts and cylinder base nuts to the specified value for
the cylinder base stud nuts. Through bolt nuts must be torqued on both sides of the
engine, even if only one cylinder is being installed.
WARNING
Failure to torque through bolt nuts on both sides of the engine
can result in a loss of main bearing crush with main bearing
shift and subsequent engine failure.
NOTE: Through-bolt nuts P/N 634505 and 649496 have been superseded
by P/N 652541.
Nut P/N 634505 is a flanged six-point (hex) nut requiring a torque value
of 690-710 inch-pounds. Nut P/N 649496 is a flanged six-point (hex) nut
requiring a torque value of 790-810 inch-pounds. At engine overhaul, all
P/N 634505 and P/N 649496 flanged through bolt nuts must be replaced
with 652541 flanged twelve-point nuts. If replacing P/N 634505 and P/N
649496 with 652541 in less than a complete set prior to engine overhaul,
torque the 652541 twelve-point nuts to the torque value of the original
fastener (P/N 634505 or P/N 649496).
3. Torque through-bolt nuts on both sides of the engine to the specified torque value.
4. For engines which incorporate the seventh cylinder deck stud, install the seventh stud
cylinder bracket and conical stud nut. Torque the stud nut to the value specified for
the fastener.
Summary of Contents for IO-240-A
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