What will happen if Tappet Clearance is less or more?

Consequences of less tappet clearance:

1. Valve will open early & close late
2. Air induced through inlet valve may leak out. So less air for combustion.
3. Power will be reduced.
4. Fuel consumption will increase, engine may become unbalanced, exhaust temp. will be very high.
5. In worst condition, valve may remain open, resulting in loss of compression pressure, burning of exhaust valve, T/C fouling will increase.

Consequences of more tappet clearance:

1. Valve will open late & close early.
2. Lesser heat energy to T/C, so reduction in scavenge air & hence power.
3. No proper removal of gases.
4. Hammering of valve stem-may cause damage to valve stem.