Valves
Valves with slight signs of wear should be sanded in a car service, and then lapped. Before lapping, make sure that the cylinder head, valve seats and bushings are in satisfactory condition and do not require repair or replacement. The valve is lapped with a suction cup to make contact with the valve head. Lapping is carried out manually on a finely dispersed lapping composition until a polished belt appears on the chamfer of the valve head and seat. After lapping, remove any remaining compound and mark the valve so that it can be installed in place during assembly.
Valve train parts
Springs, plates and crackers cannot be repaired; if severe damage is found, replace these parts.
Cylinder head
Cylinder head restoration work (grinding, replacement of seats and bushings) carried out in a car service.
Valve guides
Attention! If the bushings have been changed or repaired, the valve seats must be reground.
Replaceable bushings mounted on aluminum alloy heads (which are supplied as spare parts), on heads cast from cast iron, cast-in bushings are used. There are 4 types of repair of valve guide bushings: knurling, installation of inserts, deployment of bushings and replacement.
The first of the methods is the cheapest, but the knurled sleeve can withstand a relatively small mileage. When repairing by installing inserts, the sleeve is drilled under the bronze insert (spiral type, under which a thread is cut in the drilled sleeve) or under a thin sleeve. The insert is then deployed to fit the stem diameter of the new valve. When repairing by reaming bushings, an oversize valve will be required (spare parts are supplied with valves with a stem diameter increased by 0.076 - 0.762 mm, the most commonly used repair valves with a stem diameter increased by 0.381 mm). To repair the cast-iron head, it is necessary to drill out the cast-in bushings and expand the holes for the new ones, which are pressed in. Here you will need special equipment that ensures the centering of the sleeve hole with the valve seat, otherwise the valve seat will not be able to be reground. Repair sleeves are pressed in with a hammer and a stepped mandrel from the outside of the cylinder head. If the new bushing is to seal the coolant passage, the bushing must be pressed in with the recommended sealant.
Valve seats
Regrinding of saddles is carried out in a car service. If the seats are in satisfactory condition, then you can proceed to grinding the valves and further assembly.
Attention! The valve guides must be repaired before regrinding the seats (if it is required).
Cylinder head
If the split plane of the head is severely deformed, replace the head. Sometimes the plane of the head with a slight deformation can be restored by grinding.
Attention! After grinding the plane of the cylinder head of the overhead valve (HE IS WITH) engines should be checked and the camshaft beds centered. Otherwise, serious damage to engine parts is possible due to the collision of valve heads with piston crowns.
External mechanical damage to the cylinder head
Cracks are eliminated on both aluminum alloy and cast iron heads by installing threaded cone inserts along the crack. On aluminum alloy heads, repair by welding is also recommended.