For 1990-2009 cars

### Valve Cleaning and Inspection

Important: Do not scratch the valve stem with the wire brush.

1. Clean the valves of carbon, of oil, and of varnish. Remove carbon with a wire brush.Remove varnish by soaking the varnish in Parts Immersion Solvent GM P/N 12345368 or in an equivalent.
2. Clean the valve guides.
3. Inspect the valve stem for wear. The valve stem end may be reconditioned by grinding.
4. Follow the grinder manufacturer's instructions. Ensure the new surface is perpendicular to the valve stem.
5. Inspect the valve keeper grooves for chipping or for wear. Replace the valve if chipped or worn.
6. Inspect the valve face for burning or for cracking. If pieces are broken off, inspect the corresponding piston and the cylinder head area for damage.
7. Inspect the valve stem for burrs and for scratches. Burrs and minor scratches may be removed with an oil stone.
8. Inspect the valve stem for straightness, and inspect the valve head for bending or for distortion. Use V blocks. Replace bent valves or distorted valves.
9. Clean the deposits from the valve face. Inspect the valve face for grooving.
10. Replace the valve if the face is grooved. Valve faces cannot be machined. If worn, or damaged, the valves must be replaced.
11. The valves may be lightly lapped to the valve seats.

### Cylinder Head and Gasket Surface Cleaning and Inspection

1. Inspect the cylinder head gasket and the mating surfaces for leaks, for corrosion, and for blow-by. If the gasket has failed, use the following faults in order to determine the cause:

• | Incorrect installation

• | A loose cylinder head or a warped cylinder head

• | Dowel pins that are missing, off location, or not completely seated

• | Corrosion in the seal area around the coolant passages

• | Chips or debris in the cylinder head bolt holes

• | Bolt holes in the cylinder block not drilled or tapped deep enough

• | Other

2. Inspect the cylinder head gasket surface.

• | If corrosion is found only outside of a 4 mm (0.375 in) band around each combustion chamber (1), you may reuse the cylinder head.

• | If the area between the valve seats is cracked (2), replace the cylinder head.

• | Replace the cylinder head if you find corrosion inside a 4 mm (0.375 in) band around each combustion chamber (3).

Important: Do not use a wire brush on any gasket sealing surface.

3. Clean the cylinder head. Remove all varnish, soot, and carbon to the bare metal.
4. Clean the valve guides.
5. Clean the threaded holes. Use a nylon bristle brush.
6. Clean the remains of the sealer from the plug holes.
7. Replace all problem bolts.
8. Inspect the cylinder head for cracks. Check between the valve seats and in the exhaust ports.

Important: Do not attempt to weld the cylinder head, replace the head.

9. Inspect the cylinder head deck for corrosion, for sand inclusions, and for blow holes.
10. Inspect the cylinder head deck surface for flatness.

Maximum Cylinder Head Deck Warpage
Maximum Warpage: 0.05 mm (0.0020 in)

11. If the warpage is greater than the maximum allowed, replace the cylinder head.
12. Inspect all the threaded holes for damage. Threads may be reconditioned with thread inserts.
13. Inspect the sealing surfaces.
14. Inspect the surface of the cylinder head intake manifold for flatness.

Maximum Cylinder Head Intake Surface Warpage
Maximum Warpage: 0.05 mm (0.0020 in)

15. If the warping is greater than the maximum allowed, replace the cylinder head.
16. Inspect all the threaded holes for damage. Threads may be reconditioned with thread inserts.
17. Inspect the sealing surfaces.
18. Inspect the surface of the cylinder head exhaust manifold for flatness.

Maximum Cylinder Head Exhaust Surface Warpage
Maximum Warpage: 0.05 mm (0.0020 in)

19. If the warpage is greater than the maximum allowed, replace the cylinder head.
20. Inspect all the threaded holes for damage. Threads may be reconditioned with thread inserts.
21. Inspect the sealing surfaces.