Remove the cylinder head but before that, turn the flywheel to TDC or 5 degree and try move the timing belt from the cylinder head without turning the flywheel by loosing the tensor. Make sure that you also see the mark on the tappet pulley that inline to mark on the body of the cylinder head or mark with mark ink or center punch inline if not shown on the body of the cylinder head. Once the head remove, then try measure the valve clearance before removing any valve so you can use the clearance unit when you return the valve. Now you can change any damaged valve.
Hope this piece of message can assist you, please advise if any further assist.
