Leaking brakes, re-flare?
and go back to the stock distribution block
IDK if it's a good idea to do that, because
the All-drum D-block, does not provide any rear brake proportioning.
If the rear brakes lock up in a hard pedal application, you will lose directional stability. It's been said that once the back-end is about 7* stepped out, with 4 same-sized tires, this pretty much guarantees a spin.
IDK how accurate that is, because not a chance would I ever run 4 same-sized tires on a hotrod.
But I can tell you that under modest power, 7* will do the same thing. 7* leads to 14* leads to 21* in rapid succession, and there is almost no chance to recover from that, unless you are on a wide-open parking lot, lol.
Our cars do not require a whole lot of braking on the back, as shown by the factory not wanting to give any more than 15% to it. The front brakes do 85% of the work, or rather, are supposed to.....
Nine inch drums running NO proportioning, can match front discs pretty well. Ten inchers proportioned, works well too.
As a Streeter, I have never needed discs on the back, so I can't help you with that.
The pedal is hard and comes back just fine. It’s really just poor stopping distance. I did just roll with the cheap semi metallic pads
With a high, hard, NOT spongy pedal, new lines and hoses;
pretty much the only reason I can see for lousy stopping is:
Friction materials, contact patches, or sizing of the caliper pistons. Well unless your A-body's trunk is full of concrete, lol.
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Personally,
on the street, I like organic pads. They seem to work better when cold. My rotors run chilly, cuz :
1) I run the front wheel-bearing on the loose side so the rotors tend to knock the pistons back into the fixed-calipers, which gets the pads off the rotors. and
2) I have 295s on the back with un-proportioned 10" drums that do most of the work. and
3) I have a High-Compression 367 with a manual trans, which gives me plenty of Compression-Braking, and I hardly even need to use the brakes.
4) plus I run generous following distances. plus
5) I live in a rural area, with only small towns nearby, as in very little traffic..
6) I mostly use the brakes for when the gas pedal application just won't get me outta trouble, lol. Those 295s in the back, I found out, do an amazing job of braking in sideways slides, lol..