Contents: Valves ⇊ Valve Mechanism Parts ⇊ Cylinder head ⇊ Valve guide bushings ⇊ Valve seats ⇊ Cylinder head ⇊ External mechanical damage to the…⇊
Valves
Valves with minor signs of wear should be ground at a car service center, 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 using a suction cup device that ensures contact with the valve head. Lapping is carried out manually using a finely dispersed lapping compound 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 Mechanism Parts
Springs, plates and crackers cannot be repaired; if severe damage is detected, replace these parts.
Cylinder head
Cylinder head restoration work (grinding, replacement of seats and bushings) are performed in a car service center.
Valve guide bushings
Attention! If the bushings have been replaced or repaired, the valve seats should be reground.
Replaceable bushings are installed on aluminum alloy heads (which are supplied as spare parts), cast iron heads use cast-in bushings. There are 4 types of valve guide bushing repair: knurling, insert installation, bushing reaming and replacement.
The first method is the cheapest, but the rolled bushing can withstand relatively little mileage. When repairing by installing inserts, the bushing is drilled to accept the bronze insert (spiral type, for which a thread is cut in a drilled sleeve) or under a thin sleeve. The insert is then reamed to fit the stem diameter of the new valve. When repairing by reaming bushings, a valve of a repair size will be required (valves with a stem diameter increased by 0.076-0.762 mm are supplied as spare parts; repair valves with a stem diameter increased by 0.381 mm are most often used). To repair a cast iron head, you need to drill out the cast-in bushings and ream out the holes for new ones that are pressed in. Here you will need a special tool that ensures the centering of the bushing hole with the valve seat, otherwise it will be impossible to regrind the valve seat. The repair bushings 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 should be pressed in using the recommended sealant.
Valve seats
Regrinding of the seats is performed in a car service center. If the seats are in satisfactory condition, then you can begin grinding the valves and further assembly.
Caution! Before regrinding the seats, the valve guides must be repaired (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 slight deformation can be restored by grinding.
Attention! After grinding the cylinder head plane of overhead valve (OHV) engines, the camshaft beds should be checked and 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 heads made of both aluminum alloy and cast iron heads by installing threaded conical inserts along the crack. On aluminum alloy heads, welding repair is also recommended.