[LATECH]

dont hammer on it as brass is soft and you could deform it and render it junk.
If you want to attempt to try an re center the valve you should loosen the line on the master cylinder for the system that is working and then go in and take a quick sharp stab at the brake pedal, listen for the valve to click, have the key on so you can see light warning light go out.You may have to jab it several times to get it to move. when you do then tighten up the lines and CAREFULLY bleed the system.Bleed the rear firststarting with the passenger rear and then the other and then go to the front. Do the pass first then the drivers side, pumping can sometimes introduce air in the system so try to gravity bleed it, justopen up the bleeder and let er go till all the air is out.
By the way is the brake system for a 40 ford or is it from the 70 ish caddy donor car? The 40 ford wont have a prop valve only a junction. If your not getting fluid in the back then either a rubber line is plugged/blocked or a steel line is flattened out. Better check into that