oil pressure problems

My 79 el camino with a 350/350 on initial start up good oil psi but when it warms up the psi drop to almost zero at idle it has new bearings and crank and been plasta gauged before startup. need help

Did you check the oil pump before you reinstalled it? Even a worn pump will pump up thick cold oil, but once it heats up and thins out, the reading drops because it doesn't have the suction. Secondly, if the pump clearance between the pump and the oil pan isn't correct, you can have the same problem. I would pull the oil pan and pump, then check the oil pump, or replace it. There not that expensive. I have a 79 elky and I just replaced a boat anchor 267 with an 78 corvette L82 that I rebuilt and my oil pressure is over 30psi @ hot idle.

Graymarki

Always install a new oil pump when you have the pan off for any reason. Yours may have a partially blocked screen. Before doing anything, buy or borrow a mechanical oil gage and sending unit, plug it in under the hood and see what you have for pressure.