NO OIL PRESSURE!!! Please help!!

[968ant]

Hello, I have a V8 Esprit, I changed the leaking oil cooler yesterday for a new item, everything went well but when we fired it up the oil light was on for about 30 seconds then went off, but the oil pressure gauge didnt move, also the engine sounded very "tappety" so I turned it off after about 3-4 mins with a view to seeking some advice, is this normal? Does it take a while for the oil pressure to build or is there something I should have done to stop air locks?

Any advice you can give will be greatly appreciated.

Thankyou in advance.

Anthony.

P.S. What oil pressure should this car run at normally??