Replacing valve guides
If the valve guides are excessively worn (limiting dimensions for wear, see subsection «Detailed Specifications»), replace the valve stems.
Press out the valve bushing on a cold engine with drift 111100, pushing the bushing away from the top of the cylinder head towards the combustion chamber.
Check the dimensions of the valve guide seat to the combustion chamber.
Check the dimensions of the valve guide seat in the cylinder head. If the valve stem seat diameter is larger than the allowable (see subsection «Detailed Specifications»), bore out the seat to the nearest oversize and press in the valve bushing of the appropriate oversize.
Heat the cylinder head evenly to a temperature not exceeding 200°C, lubricate the valve bushing with grease and press it in with drift 111120, acting in the direction from the top of the cylinder head to the combustion chamber, until the drift stops against the cylinder head. The use of mandrel 111120 ensures proper protrusion of the valve sleeve relative to the plane of the cylinder head, which should be within 15±0.5 mm (see photo).
After the final cooling of the cylinder head, ream the hole in the guide bush.
Make sure the new valve guide and valve seat are fully concentric. Sand the valve seat if necessary.
Valve seat replacement
Valve seat replacement must be carried out at a service station.
Drill out the valve seat to be replaced; in this case, it is necessary to pay attention to the centering of the drill and avoid removing metal from the valve seat seat.
Bore the valve seat seat, maintaining the predetermined amount of valve seat interference into the cylinder head seat (see subsection «Detailed Specifications»).
Heat the cylinder head evenly to 200°C and cool the oversize valve seat to minus 70°C by immersing it in liquid nitrogen.
Press the valve seat into the bottom of the cylinder head seat until it stops.
Grind the working face of the valve seat.
Grinding valve seats and valves
Check the condition of the working chamfer of the valves. In case of minor damage, it can be sanded, maintaining the proper bevel angle.
Grind the working bevels of the valve seats by hand or with a grinder.
Lap the valves to the seats and check the tightness of the valves to the seats.
After grinding and lapping the seats and valves, thoroughly wash the seats, valves and cylinder head passages, blow them with compressed air.
Check the tightness of the valves to the seats by filling the combustion chambers with gasoline, after screwing in the spark plugs.