When the guys are saying tap the valves, they mean on the valve stem to be sure that the valve isn't seized up in the head. You want to tap to insure that each valve will come off it's seat when you eventually turn the engine over.
[on edit] I see you've already turned the engine over for a compression test. You could have valves that are stuck in the open position, which would cause low compression. Tapping on the stem could free them up.
Last edited by klhansen; 02/23/2020 7:31 PM.
