216's aren't famous for lots of oil pressure, but it everything is assembled properly and the pump is good. you should see 15-20 pounds of oil pressure at idle on a cold start. Sometimes the pressure will drop considerably once the engine warms up. Have you tried running the pressure gauge directly to the oil gallery without the filter connected? Try removing the distributor and spinning the oil pump clockwise with a 1/2" drill motor, using a cut-off blade from a large straight bladed screwdriver. There should be a noticeable torque load on the drill, and the oil pressure on the gauge should rise. Are you using an original-style oil filter such as a Fram or an AC? Later type spin-on filters need a restrictor incorporated into the circuit somewhere to prevent a major loss of oil pressure to the engine.
Oil flow from the valve train should indicate that the lower end of the engine is getting at least 15 PSI of oil pressure- - - -that's the point where the oil distributor down by the driver's side oil pan rail opens up and starts oil flowing to the rocker arms.
Jerry
