'69 Cuda Poor braking

This is a '69 340 Barracuda fastback with stock power (Midland Ross Booster) front disk brakes (Kelsey Hays). The car originally came with manual front drums and was converted by a previous owner. Ever since I got the car, the braking performance was not very good and the pedal was very hard. I could never lock up the wheels. I've swapped MC's, checked the push rod length, had the booster overhauled, overhauled the calipers and tried different pads (now have EBC "Red Stuff" pads) . I've tried both the stock 1" MC as well as a 15/16" unit. I recently checked the actual hydraulic pressures at the MC and at the calipers and could only get ~500 psi with moderate pedal pressure. Pushing extremely hard, I could only get ~1000 psi. These are low pressures.
Then I realized that the stock power setup has a bracket adapter with linkage that effectively reduces the force thru the booster by 1/2 compared to a non power setup. I removed it and reconfigured for manual brakes and now have twice the pressures!! I'm sure this will give me far better braking but I'm left wondering why the supposed stock power system worked so poorly????? Any other Cuda owners having this problem??
Jim

In my experience, with the same cars,that booster requires more vacuum than the later ones so if you have a bit of a cam, they don't do so good at idle or with an automatic. With a stick and downshifting they seem to be OK.
The later single-diaphragm A and F-body unit has been working very well for me even with the 292/292/108 cam in my 360. However, with that cam I always had to blip the throttle a couple of times to evacuate the chamber, before I backed out of the carport. Since it is a stick car, this was not a problem for me.

AJ/FormS said:

In my experience, that booster requires more vacuum than the later ones so if you have a bit of a cam, they don't do so good at idle or with an automatic. With a stick and downshifting they seem to be OK ,

Click to expand...

Thanks
It is an automatic and does have a fairly moderate Hughes cam (but definitively not a wild cam)

I have the same booster set up in my 69 Dart with a 360 and a Hughes HEH2328AL. Brakes have always worked great. Only thing I see different is I'm running the 73 up style single piston calipers.

I've run several of the stock combos and have never been happy. Currently I'm liking 4 wheel dics with a 7/8 manual master. Stops great. feels like power brakes. I've run this on two cars now. If I was to run power brakes again I'd run a vacuum pump and kill 2 birds with one stone.

One way I've thought of to improve the PB braking is to make a modified connecting rod (from the pedal to the pivot lever). make it longer so it connects closer to the PB pushrod and thus increases the force on the MC to that which is very close to the direct-connected manual brake setup.

View attachment 1715264714

View attachment 1715264715

My FS FB came stock with K-H front disks. They were manual so no PB issues, but I did find that you had to change brake fluid frequently (yearly) to avoid piston corrosion and sticking that caused poor braking. I replaced many pistons over the years until I converted to '73+ brakes. Heavier, but easier to work on and much larger rotors.

I had heard that too, so when I bolted my KHers on in 99, I used silicon fluid in there. That same fluid is still in there with no problems at all.