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.

I would think the same prop valve could be used. On the manual MC swap, you may need to try a different size on your rear cylinders.

Thanks for the advice. More wecome !

My B-Body had the same 4 piston setup. I updated the spindles, rotors, calipers, and kept the original proportioning valve, master cylinder and power brake booster. My brakes stop my 6 pack just fine. I didn't think I'd have adequate vacuum with my high compression motor, but it seems real good. I think I'm using 10.78 inch rotors and premium semi-metallic pads, and with just a single piston Cuda/Challenger caliper. Hope this helps...
KK