Lycoming O-290 Operator's Manual page 68

SECTION 5
MAINTENANCE PROCEDURES
(2) Assemble piston so that the cylinder number stamped on the piston pin boss is toward the front
end of the engine. The piston pin should be a push fit. If difficulty is experienced in inserting the
piston pin, it is probably caused by carbon or burrs in the piston pin hole. During assembly,
always use a generous amount of oil, both in the piston pin hole and on the piston pin.
(3) Assemble one piston pin plug at each end of the piston pin and place a new cylinder base oil seal
ring around the cylinder skirt. Coat piston, rings and the inside of the cylinder generously with oil.
(4) Using a piston ring compressor, assemble the cylinder over the piston so that the intake and
exhaust ports are toward the bottom of the engine.
(5) Push the cylinder down onto the cylinder mounting studs.
(6) Insert a new shroud tube oil seal over each end of shroud tube.
(7) Pull the cylinder back far enough to insert one end of each shroud tube into position in the
cylinder head, and hold shroud tube so that rubber seals will enter the seats in the crankcase. Push
the cylinder all the way down.
Before installing cylinder base hold-down nuts, lubricate the crankcase thru-stud threads
with any one of the following lubricants.
1. 90% SAE 50W engine oil and 10% STP.
2. Parker Thread Lube.
3. 60% SAE 30W engine oil and 40% Parker Thread Lube.
(8) Assemble the cylinder base hold-down nuts and tighten as directed in the following steps.
At anytime a cylinder is replaced, it is necessary to retorque the thru-studs on the cylinder on
the opposite side of the engine.
(a) Tighten the ½ inch or 7/16 inch hold-down nuts to 300 in.-lbs. (25 ft.-lbs.) torque in the
following sequence: Begin with the upper right hand nut and proceed in a clockwise direction.
(b) Repeat the above steps and tighten the ½ inch hold-down nuts to 600 in.-lbs. (50 ft.-lbs.) or
7/16 inch hold down nuts to 420 in.-lbs. (35 ft.-lbs.) torque using the exact sequence.
(c) Tighten the 3/8 inch hold-down nuts to 300 in.-lbs. (25 ft.-lbs.) torque; sequence of tightening
is optional.
Some O-235 series engines employ only 3/8 inch hold-down nuts. Tighten these nuts to 300
in.-lbs. (25 ft.-lbs.) torque using the tightening sequence stated in step (a).
(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 tightened to the correct torque.
5-8
LYCOMING OPERATOR'S MANUAL
NOTE
NOTE
NOTE
O-235 AND O-290 SERIES