What Look/listen For.....................pushrod

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Guy who did my heads when I first took the heads to him a few months ago, I remember him saying that pushrod was slightly bent. I for myself saw him roll it at the time but forgot exactly what he was looking/listening for so I tried it myself recently on a flat surface and I and a friend neither of us could see or hear anything that sounded funny or anything so just what should I listen/look for that i might have missed? I even called the guy to ask him and tell him what I observed and he couldn't recall specifically either so that's why i wana make for certain rather the rod is good or not