THis post is regarding the brakes on my '64 tempest custom. I posted this on the pontiac forums and I'm still stumped!! I added disc spindles from a '69 Grand Prix, a brake booster/lines/ later style dual master cyl from inline tube, as well as their modified metering block . Per their recommendation, I added an adjustable prop valve after the metering block for the rear brakes.

Problem:
Brakes do not stop like they should. The rear brakes are fine. The fronts feel like they are not engaging all the way. WHen I stomp the pedal, it feels hard and the front brakes just do not grab like they should. The pedal is not spongy at all, and does not sink to the floor. If anything, I'd describe the pedal feel as stiff or hard.. When stopping, it kind of feels like a drum brake car does when the brakes "fade" after you stomp on them. THey do not even come close to locking up!

I am confident that I have successfully bled the system (bled with a mityvac). I also rebuilt the front calipers, there are new wheel cyl's in the rear and all the brake parts are new front/rear. I'm thinking the problem is either the booster or master cylinder or the master cylinder push rod that came with my booster. What are the symptoms of a faulty m/c?? I'm doubting the MC is at fault but I've tried about everything else I can think of. Suggestions?

I'm no expert but sounds as if you are not pushing enough Fluid Volume to in order to supply sufficient pressure to the Front Disc Pistons. I'm wondering if the Master your using has enough Plunger Displacement in that Chamber - just a guess ;o)

Can you lock the rear Drums? If you can, I would assume the length of the Master's Push Rod is adjusted correctly; if not, you may have to lengthen it.