Replacing valve guides
If one of the valve guides is heavily worn (see wear limits in subsection «Detailed Specifications») replace it.
With a cold engine, press out the guide bushing with drift 609 by moving the bushing from the top of the cylinder head to the combustion chamber.
Check the dimensions of the guide sleeve seat in the cylinder head. If the hole diameter is larger than the specified (cm. «Detailed Specifications»), bore out the socket to one of the larger sizes and install the sleeve of the appropriate repair size.
Heat the cylinder head evenly to about 200°C (no more), lubricate the valve bushing with grease and press it with drift 610 in the direction from the top of the cylinder head to the combustion chamber until the drift stops against the cylinder head. Using a 610 mandrel ensures proper protrusion «A» valve sleeve relative to the plane of the cylinder head, which should be within 15±0.5 mm (see photo).
After the cylinder head has completely cooled down, ream the bore in the guide bushing to ensure that it is exactly the correct size.
Ensure that the new guide bushing and valve seat are fully aligned. Sand the valve seat if necessary.
From model year 1978 on BMW «525», «528» And «528i» replacement of valve guides is carried out taking into account the following:
- press out the guide sleeve with drift 111100;
- the length of the guide bushings has been changed. The length of the old bushings is 52 mm. New bushings can be installed in place of the old ones.
- press the guide sleeve into the heated cylinder head in the direction from the camshaft to the combustion chamber;
- hole in arbor 111120 ensures the correct insertion depth (performance «A» bushings);
- for variable valve sleeve protrusion «A» equals 13.5±0.5 mm. Insert a 1.5 mm thick washer into the hole in the mandrel.
Valve seat replacement
Valve seat replacement must be carried out at a service station.
Drill out the valve seat to be replaced, paying attention to the exact centering of the drill and avoiding 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 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 chamfer of the valves. In case of minor damage, it can be ground, maintaining the proper chamfer 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 kerosene, after screwing in the spark plugs.