Disc brake master cyl bore size.

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tekslk

tekslk

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I have a master cyl with a one inch bore on ten inch brakes. Will this work on front disc brake conversion? These will be manual disc front rear drum on a 67 barracuda.
 
I also have another one with a 7/8 bore will either of these work?
 
yes and yes
If it bolts on, and has room for the pushrod, it will work.
The smaller bore will travel a little further, but will be a little easier to push and modulate. It is what I use.
If you like a hard high pedal, the bigger one is your guy,
Having a Residual valve is a bonus, for the rear drums
If one of them has 2 similarly sized chambers it came off a drum/drum car.
If one of them has a larger chamber, it is designed for a disc front car.
If one of them has a screw retaining the guts its is an older design.Later types have a circlip retaining system.
Bail-wire or screw-top, your choice.
Be sure to bench-bleed the M/C before installing it, and
Be sure all your brakes are adjusted close to correct before commencing the bleeding, it will make it easier.
Don't forget about the pushrod adjustment; it has a narrow operating window.Better a tad too short than too long.
 
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I used a stock 73 Dart manual disc/drum unit on my 68 GTS. Bore size 1 1/32 . I like the way it feels.
 
Guess I will try the 1 inch its chrome I may put power booster to it.
 
you don't want a residual valve for the front discs.
..if it's there,take it out
 
What cam, what engine? My 367 had power brakes with a 292/508, as soon as the Rs went up a bit, and stopped the car just fine.They say that cam is around 249@050. I measured mine, and thought it was a little smaller.The original dual-diaphragm had trouble,so I swapped it out for a single off a 73 Dart
If your M/Cs are same size reservoirs, they are for drum/drum. They will work, but you have to check the fluid more often, and as said, It's best to pull the R-valve outta the port to the front discs(usually the rear reservoir).
 
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Can't remember can specs its a comp can 504 lift 360 LA. Had to use air pump with drums hoping disc will change. If. Not I will make them manual.
 
Going to discs won't change how well (or poorly) the booster works with the vacuum that you have.
 
I was hoping the disc wouldn't take as much vacume to make them work.
 
It's too soon to worry about it.

If you pay attention,later, you will notice that almost the only time the booster does not assist, is at cold start up if the idle does not pull enough vacuum, off choke.Another time it might not work is when sitting at a long light, idling in gear, for a long time. But this is more likely to be a faulty control valve inside the booster. Almost all the rest of the time,there will be sufficient vacuum to operate the booster, provided that the check valve is doing it's job.
If you use one of the smaller bore M/Cs, the transition from fully boosted to losing boost is not dramatic. By the time it becomes noticeable You will be nearly stopped anyway.Stop worrying.
Besides; a .504 lift street cam is likely around 220 to 225 @050 so that size cam makes plenty of vacuum, once the Tport has been set.More than enough.Now if you had a short stroke Teener, um
 
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Received the kit tonight, I'm a little concerned that the instructions say for b body, do I need to be concerned about this?
 
tekslk said:
... for b body, do I need to be concerned about this?
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Yes, but you didn't state what kit you bought. Most bolt to your existing spindle, and even that varies between 9" & 10" drum cars, so I expect a B-body would be different still.
 
This is the ebay item number to the kit I bought, 231811997369 instructions say b body installation so I'm a little confused and the seller isn't available till wed, I'm hoping to have it done and running by then.
 
Looks like the 1973+ front disk kit, including spindles. But, they somehow got the integral hub-rotor made w/ studs on a 5 x 4"D bolt circle. The standard rotor from a parts store would be 5 x 4.5"D bolt circle. My guess is they custom-ordered from the factory that way, or somehow bought the rotors undrilled and drilled their own stud holes. I don't know if the center register hole for the wheels is bigger in 1973+ cars. If so, they probably did even more customization.
 
That's definitely a 73+ disk kit. They must have gotten the rotors as blanks as Bill suggested.

Also, the center register for the 73+ disks is significantly bigger than any of the SBP stuff. It appears they turned down the outer register, and quite severely at that.

The track width would be wider than the usual SBP brakes too.
 
tekslk said:
Does this mean I'm gonna have trouble or will it work?
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It should work, I'd be a little concerned about the strength of that turned down hub but realistically it's probably fine. Your issue will be getting another set of those rotors. They're custom. So, only that guy on eBay has them. The good news is the rest of the parts are just the standard BBP 73+ parts, so a regular 73+ rotor will bolt right on. But then you'd lose the SBP.
 
New problem:
The front tires now rub the back part of the fender with the outside of the tread, what could have caused this because I never had a rub issue before? Its consistant on both sides.
 
The track width is wider for the 73+ disks. The SBP rims don't have enough backspace.
 
How do I fix this new tires that I just put on are no good? If I go from a 235/60/15 to a 215/60/15 will that fix me up? Or do I need new wheels?
 
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