12-14 To fit valve seat inserts

To fit valve seat inserts 12-14

1 Remove the valve guide and clean the bore into which the guide is to be fitted. 2 Fit new partially finished valve guides, see operation 12-11. 3 With the bore of the new partially finished valve guide used as a pilot, machine the recess in the cylinder head to the dimensions shown in data and dimensions at the end of this section, or machine out the old insert. Remove all debris and clean the insert recess. 4 If the bottom face of the cylinder head has been machined, the insert will have to be surface ground on the back face to ensure that there is no protrusion of the insert above the bottom face of the cylinder head. After the back of the insert has been ground, ensure that the outer edge of the back face has a 0,9/1,3 mm (0.035/0.051 in) chamfer at 30° to the vertical. 5 With the bore of the new, partially finished, valve guide used as a pilot, and with the rear face of the insert towards the cylinder head, press in the insert with the valve seat insert tool, see data and dimensions. Do not use a hammer on the insert and do not use lubrication. Use a hydraulic press or a hand press in one continuous movement. Ensure that the bottom of the insert is in contact with the bottom of the recess. 6 Ream the valve guide and cut the valve seat at an included angle of 88° for 46° valve seats or 118° for 31° valve seats, see operation 12-13. Ensure that the depth of the valve head below the face of the cylinder head is within the production limits, see data and dimensions. Work as near as possible to the minimum figure to allow for future wear on the valve seat.