I have a 1969 Coronet. It has Bendix 4 piston disc brakes. The old calipers are shot and so I changed to the new style. Can I use the portioning valve from the 4 piston brakes? One more thing, I switched from power to manual master cylinder due to low vaccum problems. I have already made the change but my brakes are not as good as I feel they should be with all the changes. I have tried bleeding the brakes but the brake peddle still seems very spongy even after I installed a 10 psi residual valve. Any help would be great.