radiator help, advice and a miricle needed please

I've moved the radiator from the front to the back, the radiator is higher than the engine, header tank in higher than the radiator, I have the lower hose running under the car with a gradual forward gradiant and the top hose through the car, however it's just pressurizing and not flowing! Could it be because I reduced part of the lower hose size (used a metal pipe) or is there some other reason staring me in the face that I haven't seen? It's not the head gasket as I've have all that checked, any help, advice would be grate guys, thanks.

I had that set up on my olld series1 v8.
it took a bit off arseing about to get all the air from the engine, i didnt have a heater so used to back fill it through the pipes.
You could get a inline pump which would give good circulation

Hi,
Thanks for the reply and thoughts/advice, after many attempts of bleeding the system from everywhere, radiator, header tank and believe it or not even the temp sensor!! I now have a good flow around the whole system (lol made visable thanks to food colouring)