I'm putting my engine back together and went to adjust the rockers and noticed the push rods can be pushed in about a half inch, just with some light pressure by hand, as if their on springs. They spring right back when released. I used comp cam hydraulic lifters. When I rotate the engine the valves all open and close so I know the rods are sitting on the lifters. Is it normal for them to spring like that? If it is how do I adjust the rockers?