I have a 47 coupe original flathead but new fuel system, electric carter pump and tank and lines are new. It has never run well, has dual 97’s and fuel regulator. When I turn the key on I get 5 psi if I open the regulator up. When I crank it I lose all fuel pressure and it won’t start. I’ve turned the psi down to 3.5 where I want it and still nothing. I then blocked off the rear carb and fuel line straight to the front carb and same issue. Any ideas?