[NeighborsComplaint]

Sounds to me like you have one lifter at zero lash and the plunger is hitting the retainer. Go over your valve lash again and check the preload. Also check for rocker arm/head interference if you're running 1.65 rockers. Look for rub marks up and down the pushrods. Check pushrod/guideplate fit/alignment. Pushrods should spin freely in the guide plate slots. Lack of clearance there can bind the pushrod enough to keep it unseated and cause what sounds like a collapsed lifter. If the knocking persists, move to the bottom end.

If you turn the engine over with the damper bolt with accessories attached against valve spring tension, it's not going to tell you much. Disconnect, the belts, pull the plugs, loosen all the rocker arms and then rotate the engine from the balancer bolt slowly feeling for any scuffing or roughness/binding during rotation. The engine should rotate smoothly requiring only even pressure to rotate. There should not be "spots" where the engine rotation binds. Rotating the engine slowly, the movement should feel uniform and fluid.

Since you are changing rocker arms anyway, you should do the bottom end check after removing the old rocker arms, then go back to the rockers, pushrods/guideplates.