Tappet clearance is a space between the top of the valve stem and the rocker arm. ... Its purpose is to allow for some mechanical expansion and lengthening of the valve stem and push rods as the engine warms up.

Why is tappet clearance important?

Why tappet clearance is necessary

It accommodates the thermal expansion of the valve's axis (spindle) that is caused by the heat of the ship's engine when in operation. It ensures the closing of the ship's valve regardless of temperatures and working conditions.

What will happen if tappet clearance is less?

So less air for combustion. Power will be reduced. Fuel consumption will increase, engine may become unbalanced, exhaust temp. will be very high. In worst condition, valve may remain open, resulting in loss of compression pressure, burning of exhaust valve, T/C fouling will increase.