440 wrist pin noise?

I have a 440 duster and it started to make a sound 45 seconds after starting that was only on the passenger side that sounds like nuts and bolts rattling in a metal coffee can. At first I thought it was a broke valve spring but I was wrong. I have no way of removing the engine so I took the oil pan off cause someone said it was a wrist pin. Well I took the oil pan off and its was clean. No sludge no metal flakes if any size. The piston rods were tight and everything looked perfect. If there is damage or something wrong with it would I be able to see the damage? What should I look for? Also I had the exhaust manifold welded a while back because it was grinder down and it blew threw. They put a peice of metal to strengthen it but it's all cracked. The sound was coming from the middle right where the exhaust manifold was fixed. Thanks for any and all help. I have no one to ask that know anything about this.