A) EFFECT OF EXCESSIVE TAPPET CLEARANCE :-
- CAUSE THE VALVE TO OPEN LATE AND CLOSE EARLY IN THE CYCLE.
- REDUCE THE MAXIMUM LIFT OF THE VALVE.
- CAUSE NOISE, AND EVENTUALLY DAMAGE, FROM THE IMPACT OF WORKING SURFACE.
B) EFFECT OF INSUFFICIENT TAPPET CLEARANCE :-
- CAUSE THE VALVE TO OPEN EARLY AND CLOSE LATE WITH INCREASED MAXIMUM LIFT.
- IN EXTREME CASES, IT MAY PREVENT THE VALVE FROM CLOSING COMPLETELY AS IT EXPANDS OR BED IN. THIS , IN TURN, WILL CAUSE HOT GASES TO BLOW PAST VALVE FACES, CAUSING BURNING OF VALVE, LOW COMPRESSION, ETC.