A year or so ago I put a 1975 disc brake front end on my '65 F 100. I used the 1975 Brake system complete with proportioning valve and vacuum booster. The old vacuum booster had a vacuum leak that got worse over time until I detected it recently and replaced the booster with a rebuilt one. Now the brakes seem really "sensitive". Is this something I need to get used to, or are there adjustments or other actions I can take to mitigate this?

 

Pull the master back off the booster ( leave the lines hooked up)
You can move it forward a bit like that

Take a flashlight, and look in where the master sits in the booster, you see a screw. Turn that in, 1 turn at a time ( or out).
Keep putting the master back on, and off, with a road test in between, until the brake "hookup" is just right

 

Sounds like what I am doing. But it still appears that I will have a mental and physical adjustment to make since it sure takes a lot less pressure to stop. Will play with it some more, but I think I am close to the "optimum" adjustment. Thank you for the responses. After this, the installation of a DS 2 ignition system on my inline 6 300. That should be fun!

 

There is also an adjustable proportioning valve avalable.
I have used that in the past on the Mustang II front ends,

I have a 90 F 250 that I finally gave up on, and came to accept that it likes to slam the brakes.
No matter what I do, it slams them on.

 

Thanks for the tip on the adjustable proportioning valve. I will look that one up on line. Had not heard that one before. I suppose I can get the hang of sensitive brakes, it has gotten better with time, experience and adjustment - but what a difference from the old leaking vacuum booster.

 

It's better than the heart stopping reality of feeling the brake-pedal hit the floor without resistance from a leaking master-cylinder... When you shut your eyes and brace for impact more than once on a drive, you know it's time to replace a few things.