Processing of valve seats in the cylinder head

Valve seats with increased wear and burnout can be machined on all engines as long as the correction angles and seat widths can be maintained. A swivel tool is used to process valve seats. It is better to entrust these works to the service station.



Valves with reduced height H of the valve edge must be replaced. Minimum edge thickness on a 520i model prior to April 1990 (M20), 535i/535i:

• Exhaust valve: H = 2.0 mm;
• Inlet valve: H=1.3mm.

When machining the valve seat, ensure the specified width of the valve seat by machining the correction angle (See table 1 on the next page).