What do rocker arms do?

a rocker arm is the arm that sits on top of the valve stem and connects to the push rods 'the push rods sit on the cam so when engine is running, the push rods go up and down in a timed sequence and...

Something is broken, bent, collapsed, or out of adjustment.

They usually break in half

Hold the pushrod between your thumb and forefinger feeling for up and down movement as you tighten the nut. When the pushrod has no up and down movement, that's zero backlash. If the cam has...

Yes they can depending on which ratio rocker arms you get.