Just replaced my head on my 01 Xj and in another post I complained and top end noise.. pulled my valve cover and discover I could move all my rockers what causes or caused this keep in mine rockers are new as well as pushrods less then 150 miles

 

First make sure all your pistons are at the top of the cylinder before you torque the rockers.
They also have to be tightened to the proper torque and in the correct firing order.
Make sure all your rocker arm pivot are the same. I had a hell of a time finding the same style pivots at different parts stores.
Some of my existing rocker arm bolts were too long for the new head casting. Maybe because a machine shop lost some of my bolts and used something they had around for my old head. Had to get new rocker bolts that were the proper length.