SECTION 5 LYCOMING OPERATOR’S MANUAL
MAINTENANCE PROCEDURES O-320 SERIES
(6) Install a new shroud tube oil seal on the crankcase end of each shroud tube and fit a new annular
ring in the groove provided in the rocker box and of each shroud tube. Install each shroud tube
through rocker box and seat the end firmly in the crankcase. Place a spacer, two springs, a lock
plate and nut over the stud provided in the rocker box and secure both shroud tubes in place.
Bend the tang of the lock plate to prevent the nut and spring from loosening.
(7) Assemble each push rod in its respective shroud tube, and assemble each rocker in its respective
position by placing rocker between bosses and sliding valve rocker shaft in place to retain rocker.
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, remove the push rod and insert a longer or shorter push rod, as required, to correct
clearance.
NOTE
Inserting a longer push rod will decrease the valve clearance.
(9) Install intercylinder baffles, rocker box covers, intake pipes, rocker box drain tubes and exhaust
manifold.
5. GENERATOR OR ALTERNATOR DRIVE BELT TENSION.
Check the tension of a new belt 25 hours after installation. Refer to latest revision of Service Instruction
No. 1129 for methods of checking generator or alternator drive belt tension.
5-10
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