I picked up a 400 engine with low miles on it. When I pull the valve covers the rockers have some slop on the rockers with the valve lifters on the bottom of the cam lobe. This motor has never been apart and I'm wondering if that's the norm without the lifters pupmed up. Now I pulled a 351M out of my truck, and the rockers are so tight there is no movement at all on the rockers that are at the bottom of the lift. These heads look rebuilt. If the heads were milled, aren't the pushrods supposed to be shortened? I pulled this motor cause the bottom end is weak.