Could be a lifter, or rocker arm or a number of things. What you can do if you don't have a stethoscope is get a long screwdriver and place the metal end on any area you suspect noise coming from. But first DO NOT wear loose clothing or jewelry. It can get caught in the belt and pull you in. Crank the vehicle, while it's idling place the driver on the valvecover for example. Then while holding it there place your ear on the handle. If you have noise there you will hear it .