Valve lash adjusters or lifters. If they aren't pumping up you will here a ticking/tapping sound that increases with engine speed. If the thing has been sitting for a while, there is likely quite a few noises you'll hear until you get good oil circulating around through the thing. A couple starts/runs/cool downs before you pass judgement. Change the oil and run it a few times. Hold the rpms @ 2000 for a minute or so then let it idle for a few minutes and repeat. I wouldn't drive it just yet until the engine quiets down some (which it hopefully will with fresh oil).