LENGTH OF THE VALVE-ROD.
To prove the correct length of the valve-rod, the rocker-arm is set at right angles to the valve-seat, which is its middle position. The valve must now stand on the middle of the seat, which will be indicated by the tram point reaching the dividing point between a and b. Should the valve not be right when the rocker is in its middle position, the rod must be altered to put it right.