I have a rattle near the top of my engine and can't figure out where it is coming from.

You know we can't hear it over a computer. Start by checking the oil level. If it's low, the pump will suck up air and the oil pressure will drop. That will allow the valve train to make a rattling noise.

There's dozens of other things that can cause rattling noises. Most of the time a mechanic can give you an idea of the problem, but he has to listen to it.