Uh Oh !! Bad knocking !!

When you pull the rocker shaft bolts out, check to see if they are stretched. I torque mine to 18 ft lbs and that was enough to stretch them after having the rockers on and off a few times. Upgrading to new bolts is easy and cheap insurance if you're pulling the rocker shafts off anyways. MrJLR hit the nail on the head about over torquing the bolts!