Which master cylinder bore size to use for power disc Kelsey/Hayes

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If all the pistons aren't firmly seated against pads, with the pads in full contact with the discs, there can be voids holding air.
Lotsa folks bleed till "blue", lol, cuz it takes a buncha pumping to get all 4/8 pistons in total contact with the pad, and more pumping to then move the pads out to disc.
You may not have got all the air out, and pads etc not all the way out when you bled before. Try bleeding it now, and make sure a pad isn't hung up and not sliding into contact with disc.
I've had a pad in wrong, kinda cockeyed, and the piston was bending the pad instead of applying braking, - giving a poor pedal.
If you have a seized piston, common on k/hs, I used to pull the pads and carefully twist the piston in the caliper, with water pump pliers to check them.
Just musing, good luck.
 
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Vinny said:
Are the bleeder screws at the top? I don't know if the left and right can be inadvertently switched? It's worth a look.
Click to expand...
Yes they can be installed upside done. Bleeders up. Some of the 70's pads can be installed backwards. A friend of mine wanted to do his own brake job and after taking it for a test drive (I call it seating the pads), he says to me, "they are worst than before". I took a look and YEP, they were metal on metal.
 
Swinger 340 said:
Yes they can be installed upside done. Bleeders up. Some of the 70's pads can be installed backwards. A friend of mine wanted to do his own brake job and after taking it for a test drive (I call it seating the pads), he says to me, "they are worst than before". I took a look and YEP, they were metal on metal.
Click to expand...
Someone put pads on metal side toward the rotor?
 
cudajim said:
My 67 Barracuda has stock Kelsey Hayes power disc brakes were stolen from a 68 Valiant. I got the brakes, master, prop valve all at once. Only problem is that the fronts don't grab well/rears lock up and the pedal is not so firm. The master also leaks from the top due to rust so it's time to change it anyway. My question is, what size bore should I buy and how do I get it to stop properly?
Click to expand...
Adjust your Proportional Valve
 
Inertia said:
If all the pistons aren't firmly seated against pads, with the pads in full contact with the discs, there can be voids holding air.
Lotsa folks bleed till "blue", lol, cuz it takes a buncha pumping to get all 4/8 pistons in total contact with the pad, and more pumping to then move the pads out to disc.
You may not have got all the air out, and pads etc not all the way out when you bled before. Try bleeding it now, and make sure a pad isn't hung up and not sliding into contact with disc.
I've had a pad in wrong, kinda cockeyed, and the piston was bending the pad instead of applying braking, - giving a poor pedal.
If you have a seized piston, common on k/hs, I used to pull the pads and carefully twist the piston in the caliper, with water pump pliers to check them.
Just musing, good luck.
Click to expand...
That's interesting, I'll look into that when we get a warm day and a good helper.
 
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