No oil pressure after reconnecting oil cooler lines

[Goopie 18]

I have a Roush 427R (351 W). Had to replace mechanical fuel pump. In order to get at it, had to remove oil cooler lines from block adapter. After replacing pump, I replaced the oil cooler lines to the block. I made sure the outlet line was connected to the outlet port of the adapter(turned engine and saw which port pumped oil). The outgoing line then was connected to the oil filter housing(paid attention to the direction arrow on filter housing). From the oil filter housing the return line goes through the cooler then back to the engine. I now have no oil pressure showing on my gauge. I turned the engine over several times (coil disconnected) to fill the lines. Then I connected the coil. Engine started and I ran it for about 10 seconds. No oil pressure showing on gauge. Does it take a long time for the oil pressure gauge tube to fill with oil to get a reading? Did I do something wrong? Don't want to run the engine for a long period of time If I messed up on the above work.