Chevrolet Cobalt Service & Repair Manual: Engine Valves R&R

Valve stem oil seal alignment and position is critical. An improperly installed valve stem oil seal may lead to excessive oil consumption, and increased vehicle emissions.
When replacing multiple valves simultaneously, mark valves in relation to cylinder/port. Keep all caps, shims and retaining components of each valve assembly together. Do not mix with other cylinder/port valve assemblies.
1. Remove cylinder head from engine as outlined in "Cylinder Head, Replace."
2. Remove spark plugs from cylinder head.
3. On models equipped with overhead camshaft, proceed as follows:
  a. Remove camshaft from cylinder head as outlined in "Camshaft, Replace."
  b. Remove valve lifter cap.
  c. Remove valve lifter cap shims if required. Ensure that shims stay with respective lifter caps and are not mixed together.
4. On models without overhead camshaft, remove valve rocker assembly.
5. On all models, tap end of valve stem with a plastic face hammer in order to loosen any varnish on valve stem keys.
6. Compress valve spring using a suitable valve spring compressor.
7. Remove valve stem keys.
8. Release valve spring compressor tension.
9. Remove valve spring cap.
10. Remove valve spring.
11. Remove spring seat shims, if equipped.
12. Remove valve. It may be required to gently tap top of valve stem to clear valve seal.
13. Reverse procedure to install, note following:
  a. Replace valve stem oil seal.
  b. Tap end of valve stem with a plastic faced hammer to seat keys, if required.
  c. Measure valve spring installed height using a ruler. If installed height exceeds manufacturer recommendation, install appropriate spring shims.
  d. On models equipped with overhead camshaft, install camshaft as outlined in "Camshaft, Replace."
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