1967 XR7 came with power drums converted to disc
pedal appears to measure correctly
booster rebuilt by (booster somebody? in Oregon) is a midland no leaks 18in vacuum
conversion kit is from SSBC rotors, calipers etc…
front brake pressure measures 2400lbs at the calipers
the problem im having is no power assist very hard brake pedal
vacuum source comes from the back of the carb
I have been fighting this for years just now getting off my dead A** to fix
I had a set of SSBC calipers that had pistons frozen in the bores. Would show great pressure, but it would not stop the rotors. Replaced them, and all worked well. These were from like 5+ years ago when they were having troubles (i later found out).
Vac source should be from manifold & not share source like brake booster, headlights,…
Thanks Bill, check valve good, I removed the engine vacuum completely, and used a vacuum pump still hard as a rock. I will check calipers, and will put vacuum supply on manifold.
Update still have hard pedal! check valve good, rod length appears good? checked pedal travel with master cylinder off, from resting position, measurement from rubber seal to end of rod is 1 1/4 pedal being pushed to the floor measures 2 5/8 a total of 1.375 travel are these some what close? I hope this helps, with trying to fix this problem, before pulling the booster, because we all love pulling boosters
Does the car stop ok? If you have brakes, just a haard pedal then that is the booster or your not getting vacuum to it. If you are not getting braking then you need to check the calipers for frozen pistons.
I put gm metric calipers (came loaded ) on my old 47 sedan . After the test drive , i was going to put the drums back on!! Seem Speedway put lifetime pads in the calipers . Went and got some cheep soft organic pad and my brakes were wonderful
Cheap brake pads make a tremendous difference, here. Even with the extra force of the vacuum booster helping, it won’t matter if an elephant stands on the brakes; they only grip as well as the pads and brake surfaces will allow.
Our cars originally used asbestos pads that lasted a long time, and had lots of friction. After taking asbestos out to prevent people from getting cancer, the replacement materials often do not work nearly as well. Fortunately, there are some new pads that still work great!
I recommend Porterfield R4-S brake pads and shoes. They wear just fine, but have a very high coefficient of friction, and will stop you like the originals did. The ‘s’ in R4-S is important - that’s their street version. Race pads tend to do poorly until they get hot!
Soooo, I did all I can, as far as diagnosis, researched different brake pads, and decided to go with EBC Green Pads. I installed pads, bedded them in per EBC, tested the brakes under normal, and heavy braking, and that is what fixed my hard pedal. I couldn’t ask for a better brake system, on an older car than what I have know. Thanks, for all the inputs.
