Note: Petrol engine valves and diesel exhaust valves are not milled, only lapping is allowed.
When milling diesel intake valves, size d = min 0.5 mm.
With properly machined valve seats and new valves, lapping the seats is not necessary.
Valves can be lapped only with lapping paste. To do this, use a rubber suction cup placed on the valve plate. To prevent grooves and marks from forming on the lapped surfaces, it is necessary to periodically separate the lapped parts from each other during the lapping process by raising and lowering the valve.
Note: After lapping, carefully remove any remaining lapping paste.
The quality of the grinding is checked by the contact patch and filling the valve with fuel. To do this, loosely seat the valve and pour fuel into the combustion chamber. Fuel should not flow out of the valve guide. Otherwise, repeat the grinding.
(This article was previously published on the resource: AUDImanual.ru)