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, oil, and varnish. Carbon can be removed with a wire brush. Varnish can be removed by soaking the valves in Parts Immersion Solvent GM P/N United States 12345368, GM P/N Canada 10953514 or an equivalent.
2. Clean the valve guides.
3. Inspect the valve stem for wear. The valve tip may be reconditioned by grinding.
4. Follow the grinder manufacturer's instructions. Ensure that the new surface is perpendicular to the valve stem.
5. Inspect the valve keeper groove for chipping or wear. Replace the valve if chipped or worn.
6. Inspect the valve face for burning or cracking. If pieces are broken off, inspect the corresponding piston and cylinder head area for damage.
7. Inspect the valve stem for burrs and scratches. Burrs and minor scratches may be removed with an oil stone.
8. Inspect the valve stem for straightness and the valve head for bending or distortion. Use V blocks. Bent or distorted valves must be replaced.
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. Use the following procedure to remove the cylinder head cup plugs:

1.1. | Obtain a suitable self-threading screw.

1.2. | Drill a hole in the plug.

1.3. | Install the self-threading screw.

1.4. | Pry out the plug and discard it.

1.5. | Remove the spark plugs.

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

• | Improper installation

• | Loose or warped cylinder head

• | Missing, off location or not fully seated dowel pins

• | 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

3. Inspect the cylinder head gasket surface.

• | The cylinder head may be reused if corrosion is found only outside a 4 mm (0.375 in) band around each combustion chamber (1).

• | Replace the cylinder head if the area between the valve seats is cracked (2).

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

4. Clean the cylinder head bolts.

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

5. Clean the cylinder head. Remove all varnish, soot and carbon to the bare metal.
6. Clean the valve guides.
7. Clean the threaded holes. Use a nylon bristle brush.
8. Clean the remains of the sealer from the plug holes.
9. Inspect the cylinder head bolts for damaged threads or stretching and damaged heads caused by improper use of tools.
10. Replace all suspect bolts.

Important: Do not attempt to weld the cylinder head. Replace the cylinder head instead.

11. Inspect the cylinder head deck for corrosion, sand inclusions and blow holes.
12. Inspect the cylinder head deck, the intake, and exhaust manifold mating surfaces for flatness. These surfaces may be reconditioned by parallel grinding.
13. Use the following steps to determine the amount of reconditioning needed:

• | If the warpage is less than 0.076 mm (0.003 in), reuse the cylinder head, but do not resurface.

• | If the warpage is between 0.076 mm (0.003 in) and 0.25 mm (0.010 in), resurface the cylinder head before reusing.

• | If the warpage is over 0.25 mm (0.010 in), discard the cylinder head.

14. Inspect all the threaded holes for damage. The threads may be reconditioned with thread inserts.
15. Inspect the sealing surfaces.
16. Inspect the cylinder head cup plugs.