Seating, Inspecting and Testing Valves

Seating Valves

Special Tools:

P 9 Suction cup, for turning valve The following points should be observed when seating (lapping) valves:


The following points should be observed when seating (lapping) valves:

  1. Seat valve with the P 9 suction cup.
  2. Use fine-grain grinding compound to prevent roughness or "grooving".
  3. Upon completion of lapping, fully remove all grinding compound remnants.


The grinding compound is water-soluble and should not be exposed to oil or grease. A special effort should be made to thoroughly clean and flush with water all involved component parts of the engine, including the valve guide bores, and then to dry and oil these prior to reassembly.

Inspecting Valves

  1. Clean valves from carbon deposits.
  2. Inspect valve face for wear or pitting. If necessary. reface on dressing machine. When refacing the valves, make certain that --especially in the case of the thermally higher stressed exhaust valves- - the dimension b (see Fig. 123) is not exceeded.
  3. Valve stems showing excessive wear (ridge formation) must be replaced.
  4. Valves with warped stems, traces of seizure, or damaged valve keeper seats must be replacad. Valve stems cannot be reground or straightened for any reason.

Testing Installed Valves For Leakage

Installed valves may be tested for leakage by pouring some gasoline into the respective port. Properly seated valves will not permit gasoline to pass through.
Last modified: Mon, 17 Jan 2005


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