Help - 216 no oil pressure!

[harrygrey382]

Just started my C15A up after doing the valves and I'm not getting any oil pressure. This is the first valve adjustment after rebuild (pump was good and all bearings/shafts measured well in tolerances). It had 25-30psi cold at idle and 5-10 hot when idling.

I pulled the valve gear off to retighten the head and it all went back on fine. After starting it and running for 15 seconds twice, still no pressure. I pulled the valve cover off to check if I'd put the rocker oil delivery pipe on properly and that's fine, but oviously no oil being delivered up there. I started it for a couple more seconds with that pipe off and nothing's coming out.

Could it be when I took the rocker gear off all oil drained back and it needs to be pumped back up and this takes time? Would've thought two bursts of running for 15 seconds would do this though. How long can I run safely with no pressure in a 216?