Did you adjust the rear brakes so they are right at the drum?  My method is to tighten the adjuster until the drum won't rotate by hand, then back off 10 clicks.

Your system should be able to develop a rock hard pedal with minimal stroke.  You have exactly what I put on Cara's 65 coupe.

Bleed in order... BENCH BLEED master cylinder.  This can be done in the car.
Right Rear
Left Rear
Right Front
Left Front.

If you have done all of the bleeding of the brakes, 9 times out of ten it is the rear brakes not being adjusted that will give you a soft pedal.

kw120 wrote:

I adjusted the rear brakes again lilike MS said bench bleed the master again and I still have very little brakes. The pedal gos 3/4 of the way down before it begins to stop. On the rears the drums do seame to get tight and loose as you rotate the drums but if I remember correctly the was the case when I bought them new a few hundred miles ago. The brakes will not pump up.  I get the same amount of brake no matter how much I pump it.  Any other ideas?
 

you mentioned "original prop valve".  66 mustang had a brass distribution block, is that what you are referring to?  factory disc brakes for a 66? , do you have a the additional kelsey hayes block too that was for a single bowl mc? 

I have a line from the rear reservoir to a T block ten lines to the front brakes. The I fave a line to the original Kelsey Hays block the a line out of it to the rear brakes. 

There were three different Fox boosters. Two adjustable and one not.  I have seen the non-adjustable versions that have a end piece on the output shaft and the end piece can be missing.  Post a picture of the booster you have and I can tell if it is the adjustable one or not.  Two are sold with the same part number, but totally different boosters that happen to bolt up the same.  One adjusts and the other does not.

The booster output shaft needs to protrude exactly 1.0" from the master cylinder mounting surface.  Any shorter and you will get alot of extra travel in the pedal before anything happens.

Is the front port on the MC going to the proportioning valve, then the rear port nearest the fireall going to the distribution block/front brakes?

There were no factory power disc brake cars in 65/66.  I think a good picture of the booster and master cylinder showing where the hard lines go would be a big help to diagnosing this.

OK, that looks correct.  It is not good to have tubing with high places, especially higher than the fluid level in the mc.  It can trap air.

Your booster is hard to discern, but it looks like the one where the master cylinder is slightly recessed into the front of the booster.  If so, that one is adjustable.  Easiest way to get it right without special tools is to remove the mc and extend the rod until the MC rocks on the rod whe you try to install it.  Then, gradually decrease the rod length until the mc no longer rocks on the rod.  That will get you to zero or just a very small gap.  Most of those boosters like that have the rod too short when you get them in the box.  Usually over 1/8" too short...  That can cause slack in the system.

Rod adjustment...  It should have a hex shaped piece on the tip of the rod, with a thin hex jam nut behind it.  Use vise-grip pliers to reach behind those parts and grip onto the smooth shaft, holding it so it cannot turn.  Then use a wrench to turn the hex to unscrew it from the rod a bit.  Turn it until you have added about 3/16" to the length.  Do not set the jam nut just yet.

Extend the rod until the MC rocks on the rod when you try to install it.  Then, gradually decrease the rod length until the mc no longer rocks on the rod.  That will get you to zero or just a very small gap.  About 0.010" gap is best.  Once you have the length set, then tighten the jam nut against the rod to keep it from turning.  Some boosters do not use the jam nut.  If no nut exists, a dab of RTV on the threads will keep it from moving.