Power Four Wheel Discs

[BASE 861]

I have a '74 with four wheel disc brakes off of a cadillac. It seems that they '76 power booster doesn't give enough boost. I am not sure if it is the master cylinder or the booster that is giving me trouble. I have to really push hard on the pedal to get this thing to slow. Alot harder than I would think four wheel discs needs. Any Ideas?

 

[BLUEovalBELIEVER]

did you change the proportioning vavle and the master cylinder?

 

[BASE 861]

I have replaced the master cylinder with a new model from a 76 as well as the prop valve. That is about it.

 

[STLKIKN]

A master cyl from a disc/ drum system may be causing your problems.
What is the proportioning valve (combination valve?) from?
When it was installed, did you reset the "pressure differential pin"
With 4 wheel disc brakes and a four wheel disc master, you probably don't need a "combination" valve. You may find that what you need is an adjustable proportioning valve like this one from Wilwood...
adjust prop valve
Is your booster working? Disconnect and plug the vac line at the intake, does the pedal feel the same?

 

[BASE 861]

The master is from a disc/drum setup. I haven't reset the prop valve(it is from a disc/drum also), I don't know how. I will check to see if the booster is working. thanks....MATT

 

[Broncoholics]

you might look intio getting the booster from the same car the master came out of.
Miss matching stuff isn't a good idea. I'd get the proportion valve from the same car and see how that works. Duff and others sell them if need be.

 

[BASE 861]

The master and the booster are both from the '76 parts truck. I will try and take the original combo valve out of the mix and test the booster. It seems now that it might just be an old booster not having enough power anymore. Will a disc/drum master be too weak for the rear discs? Thanks for all the help guys.