1994 Opel Kadett Noise from rockers after valve replacement

I replaced an exhaust and inlet valve on my kadett's head. the tensioner pulley came loose. I only replaced the two pistons which had marks on from the pistons. the rockers for these two pistons were also broken. I replaced the head gasket and all others I removed. I re-lapped the valves as well.

There is a knocking sound from the rockers. I can't be sure if it is any of the valves making this sound. This goes away when the car icles, but becomes louder when the car is revved. I am not sure if any of the hydraulic lifters are faulty or if I simply did not do something wrong when I reassembled the head.

I would really appreciate any advice.

Thanks,
John