Ok I misread your post. I see now about the scary stop with the old brakes, and the new ones not feeling right.
The adjustment check is a pretty easy procedure in most cases.
Even though you had one before, there's just no guarantee that the old and new mate up together like they did when everything was matched up. That's why the booster rods are (for the most part) adjustable.
It's basically part of the setup procedure for any master cylinder OR booster change, so for the next time you'll know. Assuming you don't forget it all years from now if it's even necessary again!
I've had master cylinders last twenty years, and there's a lot I can forget in twenty years!%)
Anyway, if your pedal traveling too much, or feels soft, it could be the rod length.
If it's actually "mushy" when the brakes are being applied, that usually indicates air is still in the system even though they've been bled.
If it's firm at the end, but still travels too far, that's usually the rod adjustment.
Unbolt the master from the booster (you can usually leave the fluid lines connected to the master for this) and pull it forward to gain access to the booster rod.
The tip is usually threaded on to the rod itself. Can you twist it by hand? If not you may have to loosen a lock nut.
Twist the rod "out" (lefty loosey) a couple of turns and start to push the master cylinder back gently until it either seats on the booster or the rod touches down on the back of the piston first. Keep turning it out until you know the rod hits home before the master meets the booster. This is indicated (obviously) by the mounting flange not laying flat against the booster.
Once you have determined it's out too far, turn the adjustment back inward until you can seat the master to the booster just before the rod touches the piston.
I have always quoted (from memory though) a 1/64th inch gap between the rod and the piston. Someone recently posted up a measurement from the Ford shop manual that was different. Much less I think, which makes sense, but makes it harder to determine by the "feel" method rather than just measuring.
Since measuring with most tools involves removing the master completely to measure the bore depth, then comparing that to the extension of the booster rod, this "best guess by feel" method has been a lifesaver for those hoping to avoid pulling the lines and bleeding again. As you can imagine.
Basically though, you want as little free-play as possible between the rod and piston. Give the pedal ratio is probably in the 6:1 to 8:1 area, even just a 1/8" of gap there will be close to an inch at the pedal!
So do your best guess to where the booster rod is seated as close to the piston as possible without actually touching it. Then drive to see what's going on.
Crossing fingers!
Paul
