The TOMEI oil gallery orifice was designed from the experience and data we had obtained from the development of our N1 endurance and drag racing engines. By restricting the diameter of the orifice to φ1.5mm (Normal is φ2.0mm) we succeeded in securing enough lubrication to the camshaft and valve while maintaining the correct amount of oil in the oil pan which resolved the common problems. (For added Blow by prevention, we recommend using the TOMEI 3D Profile pistons.)