Clatter Clatter noise from engine

[M42lover]

I have a very strange engine noise, just cannot seem to be able to pin it down. Not real loud but loud enough you hear it through the hood. Comes and goes at idle.
Head was rebuilt 10k ago, new water pump 2 weeks ago. Car has a JC chip.

Its an intermittent clattering sound which i think is coming from the top end. Power seems ok and the noise is for sure when car is idling.
My mechanic inspected the valve train when changing the rocker cover gasket, said everything was fine and cant explain the noise.
Any help appreciated.

[D. Clay]

Timing chain tensioner will sometimes do this. Sounds like the noise is in the valve train between cylinders 2 and 3.

[M42lover]

Tensioner is new, thanks for the comments, anyone else?

[strad]

My M42 had an intermittent lifter tick at idle when I bought it.  It would last for about 5 seconds, and minutes would go by with no noise.  I immediately changed the oil to Castrol Syntec 10W40 right after I bought it, and I have not heard the lifter tick since then (7k miles have gone by).

[gearheadE30]

I did a complete timing case rebuild and it still has a little bit of a clatter when it is cold. Not sure what it is, but part of it could be the injectors. Seems like this is a basic vehicle function with this many miles on the motor.