A brief guide to valve installation from MAHLE

Valves are usually low-maintenance components and aren’t among the “classical” wear parts in an engine. When everything is working fine, they do their job reliably. If the valve train gets damaged, however, there are a few things you need to watch out for during the repair. Here’s our professional advice.

Before getting started on the installation tips, check out this article about how valve damage can occur: 'A sheared-off valve'

The right way to install valves

If damaged valve train components need to be replaced, make sure that you follow these basic rules so that everything works properly and your customers are satisfied.

  • Valve impact: If a valve has made contact with the piston, then all of the valves should be replaced (Figure 1).
  • Valve guides: Installing and removing the guides means pressing them in and out. After pressing them in, they need to be reamed out to the correct dimension (Figure 2).
  • Valve keys: Do not reuse keys. If they are worn, this can cause breakage of the valve stem or limit the rotation of the valve. So you must always replace them (Figure 3).
  • Fig. 1: Bent exhaust valve
  • Fig. 2: After pressing in the new valve guide, it must be reamed to the correct dimension.
  • Fig. 3: Used valve keys should be replaced.
Fig. 4: Check used valve springs for dimensional accuracy.
  • Valve springs a): The total height and preload must correspond to the manufacturer’s recommendations. Therefore check used valve springs for dimensional accuracy (Figure 4).
  • Valve springs b): Always check that the spring is seated correctly. Therefore see our Technical Messenger(Figure 5)
  • Valve seat: When reinstalling used valves, ensure that you check the seat and leak tightness. If necessary, grind the valves with grinding paste or refinish them on a valve grinding machine (Figure 6).
  • Valve seat inserts: When installing new seat inserts, you need to mill them to the correct angle after they have been shrunk in to the cylinder head.
  • Valve stem seals: Always use the mounting device for installation, because any damage can result in increased oil consumption (Figure 7).
  • Fig. 5: Always check that the valve spring is correctly seated after installation.
  • Fig. 6: Grinding valves
  • Fig. 7: Always use the mounting device (arrow) to install valve stem seals.
  • Hydraulic valve lash compensation (hydraulic follower): Always allow sufficient rest time after installation. Wait at least 30 minutes after installation before starting the engine. Otherwise the valves will crash into the pistons when starting.
  • Valve clearance: If it is adjustable, the valve clearance must be set to the correct dimension.

More technical information about valves can be found here:

>> Types, technical terms, and installation recommendations

>> Installation poster


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