rattling noise

when i drive my truck(93 nissan pickup) i hear a wierd rattling noise in the engine i think its the belt but im not sure...
what else can it be?

that could be a million and 2 things, youll have to be more specific. i know in my 93 nissan pickup when i start it i hear a little rattling then it quiets down, but you can still hear it. it is my lifters knocking and to help it i bought some lucas heavy duty oil stabilizer and now my lifters are nice and quiet.

Check the bolts on the firewall, sometimes they loosen up and it makes a rattle that you wouldn't believe. (AC hose brackets,etc)

If its a four cyl it could be the timing chain. They usually last 150km. then the giudes break. If its the chain ,you need to replace it before the chain cuts through the cover. Then you get coolant in the oil.