clanking noise

i got a 1995 nissan truck 4x4 3.0 v-6 automatic with 115,000 miles. im fairly good when it comes to fixing stuff. i just bought this truck. it has a rattling noise, a little when you idle but more when you give it gas, but only a little gas.it sounds like its coming from the right valve cover ( if your looking at the engine) or possibly the timing cover. im hoping its a loose rocker arm. it runs fine and eberything is good except the rattle noise. it might be the timing chain, but i dont even know if it has a chain or belt, maybe you could tell me. it has no leaks or anything and runs good, but the clanking clickin noise gots me a little concerned. please help