Fokay,
I am assuming that your 216 has the little plate on the driver's side of the block and a small loop of copper tubing that loops out and into the block, just behind the plate. If you removed the front connection of that tube, that is where the oil for the rocker will come from. The plate has a device called the oil distribution valve behind it. That valve is responsible for sending oil to the rocker arm when the oil pressure has built up. There is a small feed hole that goes from under the plate area to that feed. It is quite possible for that hole to become partially blocked. Also expect to see the flow when the RPMs are up high enough to see good pressure on the gauge.
