Tappet Clearance and it's importance in engine. How to check for correct tappet clearence.

Tappet clearance is taken to ensure positive closing of the valve & for thermal expansion of the valve.

Taking all safety precautions.

Make sure the piston is on TDC.

i. From the marking on the flywheel.

ii. From the fuel cam.

iii. Push rod should be free.

Make sure the engine has cooled down.

Loosen the lock nut of the rocker arm.

Now adjust the tappet clearance between the rocker arm & valve stem by tightening or loosing the nut below the lock nut.

If tappet clearance is less:

i. Valve will open early & close late

ii. Air induced through inlet valve may leak out. So, less air for combustion.

iii. Power will be reduced.

iv. Fuel consumption will increase, engine may become unbalanced, exhaust temp. will be very high.

v. In worst condition, valve may remain open, resulting in loss of compression pressure, burning of exhaust valve, T/C fouling will increase.

If tappet clearance is more:

i. Valve will open late & close early.

ii. Lesser heat energy to T/C, so reduction in scavenge air & hence power.

iii. No proper removal of gases.

iv. Hammering of valve stem-may cause damage to valve stem.