sr20det loud rattle?

ok i was driving around one a few days ago, and was cruising at about 35mph and heard this weird noise comin from the engine. i pulled over and it sounded like rattling or a loud tick at first. so i eased it home. parked it and now it sounds like something is banging around under the valve cover. i removed the valve cover and didnt see anything irregular. took off the top chain guide and still no avail. its irratic as u can hear. sounds quite for a few seconds and then sounds like an empty spray can being rattled. anyone know wtf this is??

[Trax]

Time chain guide? Pop it off and take a look again...

[TheRotorious]

i figured it out. i changed the water pump recently and got a cheap aftermarket one. the pulley got loose somehow and put a nasty groove where it bolts to. so it was playing hoola hoop and the bolts holding it on were nearly cut in half. so a new pulley and prolly a water pump will fix it. thank god, no rod knock