[1930artdeco]

My 57 came with the interference nut and several of them lost their gripping power so I could turn them by hand. The nut would back itself out during a run and the valve would change gap. I swapped all of the rockers with a 56 and older version that had the lock nut. Locked them down tight and they don't change now. I just prefer the lock nut style a few more steps than just turning the nut and using a feeler gauge but they won't change on me going down the road.