Cylinder head repair (Chevrolet Aveo T200)

Disassembly

1. Remove the cylinder head together with the intake and exhaust manifold.

2. Remove the coolant temperature sensor.

3. Remove the exhaust manifold heat shield.

4. Remove the exhaust manifold.

5. Remove the exhaust manifold gasket.

6. Remove the exhaust manifold mounting studs.



7. Remove the spark plugs.

8. Remove the intake manifold.

9. Remove the intake manifold gasket.

10. Remove the intake manifold studs.



11. Unscrew the thermostat housing screws.

12. Remove the thermostat housing.





13. Remove the thermostat gasket and thermostat.

14. Using a valve spring compressor, compress the valve springs.

15. Remove the crackers and remove the upper valve spring plates.



16. Remove the valve springs.

17. Remove the oil seals.

18. Remove the valves.

20. Remove the camshaft housing centering bushings.

Repair of parts

For the engines described, the manufacturer provides for the restoration of the "guide bushing - valve stem" pair using valves with repair stem sizes. In this case, the worn bushing is restored by reaming to repair sizes. Work of such complexity should only be entrusted to a qualified mechanic.

Camshaft
Lifting the intake cams		6.12 mm
Lifting the exhaust cams		6.12mm
End runout		0.09-0.21 mm
Camshaft journal outer diameter	№1	39,445 mm
	№2	39,700 mm
	№3	39.945 mm
	№4	40,200 mm
	№5	40.445 mm
Bearing outer diameter	№1	39,500 mm
	№2	39,750 mm
	№3	40,000 mm
	№4	40,250 mm
	№5	40,500 mm

Inspection of the cylinder head

1. Clean the surface where the head gasket meets.

2. Check the cylinder head gasket and the mating surfaces of the head and cylinder block for cavities, leaks, corrosion and gas breakthrough into the cooling jacket.

3. Check the cylinder head for cracks.

5. Using a set of feeler gauges and a straight edge, determine the deviation from flatness of the head plane mating with the gasket, which should not exceed 0.025 mm.



6. Measure the height of the cylinder head. The height of the cylinder head should be between 94.70-95.65 mm. If the height of the cylinder head is less than 94.7 mm, it should be replaced.





7. Check all threaded holes for damage or contamination.

8. Inspect the valve seats for excessive wear and burnout.

Valve mechanism
Method of regulating valve drive		Hydraulic valve clearance compensator
The cone angle of the valve working surface (between the generatrix and plane of the head)		45°
Cone angle of the valve seat working surface		45°
Reference runout(max,all)		0.03 mm
End runout (max, all)		0.03 mm
Width of the working surface of the saddle	Intake port	1.3-1.5 mm
	Outlet	1.6-1.8 mm
Valve guide bushing inner diameter		7,030-7,050 mm
Valve stem diameter		7 mm
Valve plate diameter	Inlet	38.0 mm
	Outlet	31.0 mm
Valve spring length under load	Open valve 625 +25 N	21.5 mm
	Closed valve 275 + 15N	31.5 mm

Restoring the functionality of the valve guide bushing

1. Determine the actual wear in the "bushing - valve stem" pair. If the gap exceeds 0.1 mm, this friction pair needs to be replaced. This diagnostic operation should only be performed by a qualified mechanic.

2. The repair size code is applied to the valve guide bushing and the end of the valve stem. The table shows the standard and repair sizes, the designation of the reamer used by authorized service stations, and the content of the codes applied to the bushings and valves. There are two types of codes: the code applied during assembly of a new engine, and the code applied to the bushing during repair.

Size	Scan	Code applied to parts of a new engine	Code applied to engine parts during repair
Standard	-	-	TO
0,075	KM-253	1	K1
0,150	Km-254	2	K2
0,250	KM-255	-	A

Ream the guide bushing hole. Reaming direction is from the top side of the cylinder head. After reaming, cross out the code on the bushing and apply a new code.



Restoration of valve seats

1. Treat the working surface of the valve seats.

The valve seat sealing surface is restored using three conical cutters:

• milling cutter for processing the working surface of the saddle: 45°;
• milling cutter for processing the upper correction angle: 30°;
• milling cutter for processing the lower correction angle: 60°;

Width of the working surface of the valve seat:

• inlet: 1.3-1.5 mm;
• outlet: 1.6-1.8 mm.

2. Check the position of the valve stem end after installing the valve (without special gauges, this work must be performed by a qualified mechanic).



3. If the end of the rod is located higher (closer to the camshaft axis), the valves should be replaced with new ones and then the position of the stem end should be checked again.

4. If the valve stem end is still higher despite replacing the valves, replace the cylinder head.

Inspection of the valve

1. Inspect the valve for wear and tear, or for crushing of the upper end of the stem.

2. Inspect the valve cracker grooves and oil seal for wear.

3. Inspect the valve heads for burnouts and cracks.

4. Inspect the valve stems for wear, scoring and scratches.

5. Inspect the valve stem - it should not be bent.

6. Inspect the valve closing cone. If the wear of the contact cone is so great that resurfacing will produce a sharp edge at the junction of the conical and flat surfaces of the valve head, the valve should be replaced.



7. Inspect the valve spring. If the ends of the valve spring are not parallel, replace the valve spring.

8. Measure the valve spring height. If the valve spring height is not within specifications, replace the valve spring.

9. Inspect the valve spring seating surfaces for wear or grooving. Replace if necessary.

Valve grinding

1. Make sure there are no burnouts on the valve head cone.

2. The valve can be reground only twice. Do not ground the end of the valve stem.

3. The angle between the valve cone generatrix and the head plane is 46°.

Lapping valves

If the wear of the valve seat cone is not too great, the valve should be lapped onto a reconditioned valve seat cone (as a rule, when the valve is operating, the locking surface of the connecting rod bearings becomes wider: up to 4-5 mm). If there is no deep groove on the cone, then it is possible to grind the valve to the restored seat without grinding the cone.

The valve is ground in using special corundum-based grinding pastes.

In this case, the valve installed in the guide bushing performs reciprocating movements with simultaneous right-left rotation, alternately. Such movements are necessary to form oblique lapping lines located crosswise. During the lapping process, the valve should be periodically rotated in the seat to ensure uniform lapping. The lapping can be considered complete when a uniform matte-gray annular contact strip equal in width to the seat lapping surface is formed on the valve locking surface.

Assembly

1. Install the camshaft housing centering bushings.

2. Lubricate the valve stems with engine oil.

3. Install the valves.

4. Install the oil seals.

5. Install the valve springs.

6. Compress the valve springs and install the crackers.

7. Install the valve cover.

8. Install the thermostat.

9. Install the thermostat housing

10. Install the thermostat housing screws and tighten them to 20 Nm.

11. Install the intake manifold studs.

12. Install the intake manifold gasket.

13. Install the intake manifold and tighten the nuts to 25 Nm.

14. Install the spark plugs and tighten to 40 Nm.

15. Install the exhaust manifold studs.

16. Install the exhaust manifold gasket.

17. Install the exhaust manifold and tighten the nuts to 25 Nm.

18. Install the exhaust manifold heat shield and tighten the screws to 15 Nm.

19. Install the coolant temperature sensor and tighten to 20 Nm.

20. Install the cylinder head together with the intake manifold and exhaust manifold.

[The text of the article was obtained from the website CHEVYMAN]