Cam Knocking....

[clio172cup20]

On Tick over i have a slight cam knocking on one of the valves, are they adjustible?! if so how?!? or do i need new cams??
also.. What causes this knocking?!?!

Many thanks

 

[Fred@BTM]

non adjustable, if the top end is knocking expect a large bill

we had a 172 in that had a roller fall off so it was running on 15 valves (from new!)