Valve Cleaning and Inspection
Important: Do not scratch the valve stem with the wire brush.
- 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.
- Clean the valve guides.
- Inspect the valve stem for wear. The valve stem end may be reconditioned
by grinding.
- Follow the grinder manufacturer's instructions. Ensure the new
surface is perpendicular to the valve stem.
- Inspect the valve keeper grooves for chipping or for wear. Replace
the valve if chipped or worn.
- 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.
- Inspect the valve stem for burrs and for scratches. Burrs and
minor scratches may be removed with an oil stone.
- 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.
- Clean the deposits from the valve face. Inspect the valve face
for grooving.
- Replace the valve if the face is grooved. Valve faces cannot be
machined. If worn, or damaged, the valves must be replaced.
- The valves may be lightly lapped to the valve seats.
Cylinder Head and Gasket Surface Cleaning and Inspection
- 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:
| • | 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 |
- 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.
- Clean the cylinder head. Remove all varnish, soot, and carbon to the
bare metal.
- Clean the valve guides.
- Clean the threaded holes. Use a nylon bristle brush.
- Clean the remains of the sealer from the plug holes.
- Replace all problem bolts.
- 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.
- Inspect the cylinder head deck for corrosion, for sand inclusions, and
for blow holes.
- Inspect the cylinder head
deck surface for flatness.
Maximum Cylinder Head Deck Warpage
Maximum Warpage: 0.05 mm (0.0020 in)
- If the warpage is greater than the maximum allowed, replace the
cylinder head.
- Inspect all the threaded holes for damage. Threads may be reconditioned
with thread inserts.
- Inspect the sealing surfaces.
- 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)
- If the warping is greater than the maximum allowed, replace the
cylinder head.
- Inspect all the threaded holes for damage. Threads may be reconditioned
with thread inserts.
- Inspect the sealing surfaces.
- 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)
- If the warpage is greater than the maximum allowed, replace the
cylinder head.
- Inspect all the threaded holes for damage. Threads may be reconditioned
with thread inserts.
- Inspect the sealing surfaces.
