1956 Ford Crown Vic in shop for brake work. Installed all new brake hardware, new brake shoes, drums and wheel cylinders. The brake line and hoses were replaced about 3 years ago. Also installed new dual master cylinder and new 7 inch brake booster. After making final adjustments, the brake pedal is lower than normal and braking is somewhat acceptable. If the pedal is adjusted any higher then the brakes lock up after little brake pressure.

I have used this shop for years and they are very good. They even compared my car to another client's 1956 Ford Victoria with similar configuration but has disc brakes and are stumped by the brake height being low. Any suggestions as to why the brake pedal is low?

Is the Master Cylinder supposed to be used with Disc Brakes or Drum brakes? I seem to remember that Drum Brake masters have check Valves to maintain residual line pressure as opposed to Disc Brake Ones that don't because the return on Disc Brakes is "passive" with no return Springs etc . When U purchase an OEM Master they are different for Drum Brakes and Disc/Drum Combo. Something to ask your Installer. You can buy "residual check Valves" that can be added without changing the Master Cylinder. When I installed my Aftermarket Booster/ Master it mounted with an angled Bracket on Firewall so the Assembly was at an Angle upwards. The Pushrod was at an extreme Angle when using the existing Hole in the Pedal Arm. I drilled another Hole further down where the Pushrod met the Pedal on the downward Angle. Worked fine. Still plenty of Pedal reserve. As far as adjusting Pedal Freeplay, the Link from Pedal to Booster is adjustable by changing the Length of the Pushrod. With power off You should be able to push Pedal down by hand and  "feel" when the Pushrod comes in contact with Piston in Booster. Should be somewhere around 1/4 inch or so. The Pushrod between Booster and Master is also adjustable but should contact the Master Cylinder Piston with no Freeplay.  

  

I've had a couple occasions where the pushrods length, either from the pedal to the booster, or the booster to the master, didn't quite work out. I've seen some where the pedal ratio was part of the problem, but not on older Fords.

Some masters are bored deep for a manual set up, and require a spacer in the bore before bolting it to the booster.

The drum/drum, disc/drum, disc/disc could also be in play, along with a combination valve, or residuals. But from your description (low brakes one way, too high and hard the other) I'd revisit the mechanical linkage thru the booster to the master. There has to be some free play, I did too little once and on a hot run the brakes put themselves on as the rods heated up and got just a little longer.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ