I have hand a tick in my engine for over a year. it comes and goes. Goes away with a very slight increase in RPMs A local indie mech who works on rovers opined that it was coming from under the rocker covers and might be due to a clogged/ gunked up oil line coming into the cover. He suggested I change my oil using motor medic and adding a quart of Rislone in lieu of one qt. of 15-40. I did that and the ticking has become more intermittent. there was a long thread about cleaning the rocker covers a few weeks back. One thing that came up is that there is a baffle in the top of each rover cover held in by small screws. in my case I am wondering if the baffle is not a bit loose.
To increase my oil pressure, I am going to change the oil again using the MM and Rislone combo and the big WIX 51459 oil filter which has been touted on this forum.

 

That sounds exactly like the tick on the rocker shaft, rockers. Those parts have little holes, LITTLE HOLES, that need to be cleaned and poked with a very thin needle like tool.


I cleaned mine, poked that crud out and my tick is long gone. Others have annihilated their tick this way also.
You have to soak these parts, blow them out, really get in there and clean them. You have to be meticulous like getting the carbon off an m4...like the little holes in the carrier...soak em and blow.


As the engine ages, with proper oil changes or not, these holes start to clog, then the valve starts to make noise due to its lack of oiling.

 

Take a look at this thread:
https://landroverforums.com/forum/di...tuation-79876/
The thread author, adolfojbonilla, had some great pics and awesome insight on the dirty rocker, tick issue. He was the one who put out the idea of Motor Medic.