I have a 67 Satellite that was giving me the same issues presently. After a front drum to single piston floating caliper disc brake conversion and a complete front end rebuild, I could do a solid 2 count after releasing the brake pedal before the brakes would release. I even stopped on a hill, applied the brakes, then lifted my foot off of the pedal and the car would NOT move for a full 2 count. after much troubleshooting and talking with my brake vendor and no luck. I swapped out the new 73 & newer combination disc/drum valve back to the old drum/drum block. Completely re-bled the system (Yes, the master cyl 1st!) NOW the brakes release immediately. A new faulty combo valve is obviously the problem. Will be contacting my vendor to inform him what I found. I still need to reinstall a properly functioning combination valve to achieve the proper braking ratio. Now the car heads to the alignment shop to get everything squared up!