Alternator Drive Belt Tension - Lycoming O-320 76 Series Operator's Manual

LYCOMING SERIES OPERATORS MANUAL
O-320
(5) Install cylinder base hold-down nuts and tighten as directed in the following steps.
At any time a cylinder is replaced, it is necessary to retorque the thru-studs on the cylinder
on the opposite side of the engine.
(a) Tighten ½ inch hold-down nuts to 300 in.-lbs. (25 ft.-lbs.) torque, using the sequence
beginning with the top right nut and proceeding clockwise.
(b) Using the same sequence tighten hold-down nuts to 600 in.-lbs. (50 ft-lbs.) torque.
(c) Tighten 3/8 inch hold-down nut to 300 in.-lbs. (25 ft.-lbs.) torque. Sequence of tightening is
optional.
(d) As a final check, hold the torque wrench on each nut for about five seconds. If the nut does not
turn, it may be presumed to be tightening to correct torque.
AFTER ALL CYLINDER BASE NUTS HAVE BEEN TIGHTENED, REMOVE ANY SMALL
NICKS IN THE CYLINDER FINS BY FILING OR BURRING.
(6) Install a new should tube seal on the crankcase end of each shroud tube and fit a new shroud tube
seal in the groove provided in the rocker box end of each shroud tube. Install each shroud tube
through rocker box and seat the end firmly in the crankcase. Place a spring, a lockplate and nut
over the stud provided in the rocker box and secure both shroud tubes in place. Bend the tang of
the lockplate to prevent the nut and spring from loosening.
(7) Assemble each push rod in its respective shroud tube, and assemble each fulcrum and rocker arm
on its respective stud. Install a plain 5/16-24 nut to hold rocker in place. Before installing exhaust
valve rocker, place rotator cap over end of exhaust valve stem.
(8) Be sure that the piston is at top center of compression stroke and that both valves are closed.
Check clearance between the valve stem tip and the valve rocker. In order to check this clearance,
place the thumb of one hand on the valve rocker directly over the end of the push rod and push
down so as to compress the hydraulic tappet spring. While holding the spring compressed, the
valve clearance should be between .028 and .080 inch. If clearance does not come within these
limits, add or subtract shim under fulcrum, as required to correct clearance. After clearance is set,
remove plain 5/16-24 nut and install 5/16-24 self-locking nut on fulcrum stud. Tighten to the
specified torque of 150 in.-lbs.
(9) Install inter-cylinder baffles, rocker box covers, intake pipes, rocker box drain tubes and exhaust
manifold.
6. ALTERANTOR DRIVE BELT TENSION.
Check the tension of a new belt 25 hours after installation. Refer to the latest revision of Service
Instruction No. 1129 for method of checking alternator drive belt tension.
MAINTENANCE PROCEDURES
NOTE
CAUTION
SECTION 5
5-9