My '95 Millenia 2.5 had a radiator crack, which led to overheating.
Since then, there is a really loud knock coming from the front valve cover / camshaft area.There had been a rather mild knock from the time I bought the car, 2 years ago, but this is scary loud!
My friend Richie suggests a bearing or rocker arm problem. I will begin removing the valve cover today, but am not sure the problem will be obvious to my eye.
I made a 10 second video, if that's of any value.

 

How many miles, and post the vidio

 

I could be wrong but I don't think there are any bearings as such for the cam shaft, I think the cam simply sits on the aluminum and uses oil as a bearing surface. If the head has been damaged by overheating/lack of oil at the points where the cam sits you could possibly get it line bored and have shell bearings installed but it would probably be cheaper to simply buy another head from a scrap yard, providing it is guaranteed to be in good condition. You should also check that the cam hasn't been burned and damaged/warped at the points where it sits on the head or you'll probably need a new cam too.