The clearance upon fitting must be: maximum detected value - minimum detected value = 0.03÷0.045 mm.
The maximum permissible wear limit is 0.08 mm.
Change the valve guides when the ovality exceeds permissible limit or the valve stem clearance is outside the tolerance range.
When you change the valve guide, you must also change the valve.
Valve guides as spare parts are available with outside diameter oversized by 0.03, 0.06 and 0.09 mm.
Change the valve guides as follows: