From time to time, a rattle in the entrance of the engine doesn’t always imply the VCT equipment is worn out. The timing chain manual about the SR20 and KA24 engines is known to loosen and rattle, knocking over the valve go over as the timing chain moves beneath it. https://socialwebconsult.com/story4064077/not-known-details-about-jdm-nissan-sr20-turbo-engine-for-sale