Play in rocker arms?

[RSW]

I have recently put my engine back in having done some work on it. The work included setting the tappets etc. I know I got the gap right but now I've got the engine back in the car it still taps slightly. I was sure it was inlet valves on the air box side of the car so I adjusted them again - still no luck.

I am not to bothered as its a lot better then it was but I am looking for the reason all the same.

Could it be a rocker or two that has slight play in it?
I noticed they do slide along thier rocker shaft slightly but I've no experiance of doing anything with rockers.
If it helps, the tap seems to disapear when the revs are raised on the engine.

Can anyone tell me if this tap could be down to this reason - or suggest any other reason?

Many Thanks
Richard