It took me forever to get the oil pressure up on mine I was convinced that the oil pump had a problem, I'd never had a problem before, just filled the tank up with oil, took the plugs out and turned it over until the oil light went out.
For my F1 rebuilt I was a bit more careful and I put one litre of oil in the tank and one litre into the rocker box, then watched inside the rocker cover to make sure that oil was getting to the cam, this happened after the oil light went out so beware.
Cheers
Dennis