Genuine Nissan RB20/25/26 CAS Cam Angle Sensor Seal Only 13568-58S00

These seals are often neglected.  Cam angle sensors are usually removed and reinstalled many times along the course of an RB engine's life.  The gaskets are dried out, and britle.  

You can also order one to replace yours when you paint your flaking timing cover.  Make sure you have the three spacers between thecam angle sensor and the bracket it bolts to, otherwise you will damage the sensor itself.  The shaft that plugs into the camshaft will be forced into the housing and destroy the bearings - and running a damaged cam angle sensor will likely cause your engine to run poorly, or even knock, or result in a no start.