Lycoming IO-320-A1A Operator's Manual page 57

SECTION 5
MAINTENANCE PROCEDRUES
AFTER ALL CYLINDER BASE NUTS HAVE BEEN TIGHTENED, REMOVE ANY NICKS IN
THE CYLINDER FINS BY FILING OR BURRING.
5. GENERATOR OR ALTERNATOR DRIVE BELT TENSION.
Inserting a longer push rod will decrease the valve clearance.
LYCOMING OPERATOR'S MANUAL
CAUTION
NOTE
IO-320 SERIES