small block engine priming

You haven't told us anything. Is this a completely new engine? New cam bearings? Torn down to bare block? Or some sort of refresh/ re-ring?

There are a number of possibilities

First, is it actually pumping oil? are you getting any pressure from the sender port? Is the drill pulling hard? AND ARE YOU turning it clockwise?

Possibilities: Some block plug left out. There are at least two that are trouble/ easy to overlook. There are 3 screw in plugs in the rear of the block, and ONE of them has an INTERNAL plug that goes in first, INSIDE the block. "I've been told" some guys have actually installed this (missing) plug through the distributor hole after engine assemble

Second one is a core plug in the vertical oil passage from bottom end up to sender. It is possible to measure this "dipstick" style through the sender hole to determine if it is in place

There are of course the front cam/ lifter bores

And, is it possible you/ somebody installed the cam bearings with the holes in the bearings not lined up with block oil holes? These are also possible to verify, by GENTLY using bare brass brazing rod, inserted from the head, and "feel" and drop it through the cam as you GENTLY and SLOWY rotate the engine.

Last of course is rocker oil holes alignment, or plugged up somewhere