Improved valve adjustmentbolt for Ferrari engines

Click to enlarge


 

Disadvantages of the original valve adjustmentbolt:

 

  1. As shown, the force in the valvesprings is 1039 Newton, which equals approximately 106 kg or 233 LBS. The contact area between valve adjustmentbolt and valvestem is very small. The result is a very high load on a very small surface. This will cause the adjuster bolt to wear and the valvestem to hollow.
  2. Due to the movement of the rocker and the friction between the adjustmentbolt and the valvestem, there will be a very high sideward force on the valvestem. This will result in wear of the valveguides.
  3. The wear of the valvestem and the adjustmentbolt will increase when racing camshafts are used. This as a result of the more aggressive curve of the cams and the higher valvelift.

 

The original situation                                                    The improved situation

Standard camshaft, 9mm valvelift                                       Standard camshaft, 9mm valvelift

                                                                  F=1039N                                                               F=1039N

                   1 rocker                  2 camshaft                 3 valve adjustmentbolt            4 intakevalve                 5 cylinderhead

 

 

 

 

 

Advantages of the new valve adjustmentbolt with smaller camfollower roll and needle bearings:

 

  1. The system needs more clearance between the valvestem and the rocker. Therefore smaller rollers on needle bearings, as developed by RE, are used. The advantage of the smaller rollers is the smaller angle between adjustmentbolt and valvestem when the valve is fully opened. This reduces the sideward force on the valvestem.
  2. The force on the valvetip, exercised by the adjustmentbolt, is now spreaded over almost the entire area of the valvetip (see drawing). The advantage is that the valvestem will not get hollowed anymore and in that way the sideward force on the valvestem will be minimised. This means much less wear on the valveguides.
  3. It is no longer necessary to harden the valvetip, so the elasticity of the material will be maintained.
  4. This whole set-up will reduce friction in the valvetrain. The result is a gain of engine output.
  5. This system can be installed in all 250, 275 and 330 engine types, provided the valvetip is perfectly flat and doesn’t show any signs of wear. The advantages mentioned in points 1-4 make the system almost indispensable for racing engines with racing camshafts.