Alright. On a '57, there is a 1/8" line that comes from the rear cam journal to a port about at the center of the block, just under the deck surface. That line feeds the rocker shaft. If it's plugged, or I've also seen reports of it simply missing and the cam port plugged off, that will impede oil flow. There's also a passage and/or a special grooved head bolt in the location next to the rocker shaft feed pipe. If that's plugged or wrong bolt intalled, that will block the flow as well. A quick way to check if oil is getting at least to that point is to remove the 1/8" NPT plug that's located on the RH side of the head, about 1/2 way back from the front of the engine. If you get oil there, the line is OK. If the bolt/passage checks out, look for pluggage of the rocker shaft feed pipe.
