I did do the top end including the rocker arms, that was years ago, had a massive break between put the top end kit and actually getting the car running. Was probably 2 years in between.
Get a short piece of hose, hold one end to your ear, and move the other end around the motor, actually holding it against the engine part, till you can locate when the sound is the loudest. If that’s a valve cover, take it off and check each rocker arm to ensure it’s correctly installed. If the sound is loudest on the oil pan, you’ve got bigger problems.
I am with Limp so I would pull the valve covers and check the rockers. If you find one then its likely there are more that are either loose or not adjusted properly.
Get a short piece of hose, hold one end to your ear, and move the other end around the motor, actually holding it against the engine part, till you can locate when the sound is the loudest.