Hydrolyic Valve lifters' noise? on 1990 Mercedes-Benz 190E

My 1988 260E Mercedes is making ticking noises so I had her valve lifters replaced. The mechanics also said there were no engine oil in them, so he quickly cleaned up the oil pipes. But I still can hear the ticking noises.
Please help.

The mechanics also said that one of the camshaft lobes is scratched, could it be causing the ticking noise now? Thanks!

Asked by for the 1990 Mercedes-Benz 190E