Al_84_TOY

So I just developed this issue over the weekend. It seems liked have a pretty bad knock in the upper rear of the engine and I adjusted the valves but it's still there. I have never taken the head off and I'm the second owner. I have replaced the timing chain but that's as far as Ive dug into the engine. I ran her pretty hard wheelin but now she's got this knock. I was curious if anyone else has had this problem an if so what was it? And a fix maybe? Thanks