[jayvee43]

It's the weight of the new float, Brass is heavy and sits lower into the fuel, and the pressure from the pump doesn't help, combine the two factors lack sufficient boyancy to push up against the needle and seat and stop the flow with force.

I bet ya, you go back to your fiber float, and it will work, the few times I saw that problem was the float.

Also, (so no one asks again) is your float filling with gasoline, do the rattle in your hand and listen to seee if there is fluid in it.