I have two ? First,when I change from drum brakes on front to disc.,do I need to change to a different master also?I do know the portion valve needs changed.Second ?,are the front bumber the same for Dart and Valiant 1967----1969 ?Thanks,Lz.
Disc brakes
- Thread starter 11zman67
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Yes on the master cylinder.
Yes on the front bumper. Rear is 67 only. 68 & 69 same.
doogievlg
Well-Known Member
Really? I wasn’t aware of this.
Thanks guys.I thought the same on bumpers,wasn't sure on master cylinder.Why is that?
JDMopar
Well-Known Member
A disc brake master cylinder has different valving (is that a word?) than a drum master cylinder. If your drum master cylinder is good, you can get away with performing a little change to it, and using it until the end of it's life. This may be hard to visualize without pics, but it's not hard to figure out if you have a drum brake master cylinder in your hands. Remove the brake line from the reservoir that feeds the front brakes, and look into the hole it came out of. You will see a round metal seat with a small hole in it. Take a sheet metal screw that will thread a little ways into the hole and tighten up just a little without distorting the hole. Take a pair of pliers and wiggle the seat out....and save it. Under that seat is a rubber hickey with a spring that looks like a spring in an ink pen. Take those out and throw them away. Take the seat that you removed, and remove the screw you used to pull it out. Then place the seat back into the hole it came out of, and reinstall the brake line and tighten it up. That will put the seat back where it needs to be, but take the line back loose and double check to make sure. When you're satisfied that it's seated back, bench bleed the master cylinder and then bleed the brakes. This was the subject of an article in one of the Mopar magazines a long time ago. I did it to a Duster that I converted to 73 and up discs a long time ago. It worked fine, and was on the car when I sold it. If your existing master cylinder is iffy....just buy a new one for a disc brake car that would have had the brakes you're using. Good luck.
Yes. The pressure is different as well as the reservoir capacity(slightly)
doogievlg
Well-Known Member
My master cylinder is almost 45 years old so I recon it couldn’t hurt to replace it. Next dumb question is that since my brakes came off an aspen am I still ok running a master cylinder off a factory disc brake dart from 73?
I'd get whatever master cylinder matches the car the proportioning valve is from, though I don't think they'd be far apart
Thanks JDMopar
67Dart273
Well-Known Member
OK let's clear the air. The "pressure" coming from a drum disk master is NO DIFFERENT unless you change the bore size. Larger bore= more pedal pressure/ more movement at the brake end
The valving that is different (posted above) is the RESIDUAL VALVES. On my 67, with 4X disk brakes, I merely punctured the valves with a nail and "tried it." It worked great. The residual valves DO NOT CHANGE the proportioning.
Moreover, drum systems DO NOT HAVE a prop valve. What you may think is one, is simply a piston switch which turns the warning lamp on in case of differential pressure in the two sets of lines
THIS IS DETAILED IN the service manuals which I've posted a gazillian times..........go download them free at MyMopar. Some of them there came from the guys HERE
For info on the late model disk setup and prop valve, you will need the 1973 manual
The valving that is different (posted above) is the RESIDUAL VALVES. On my 67, with 4X disk brakes, I merely punctured the valves with a nail and "tried it." It worked great. The residual valves DO NOT CHANGE the proportioning.
Moreover, drum systems DO NOT HAVE a prop valve. What you may think is one, is simply a piston switch which turns the warning lamp on in case of differential pressure in the two sets of lines
THIS IS DETAILED IN the service manuals which I've posted a gazillian times..........go download them free at MyMopar. Some of them there came from the guys HERE
For info on the late model disk setup and prop valve, you will need the 1973 manual
BillGrissom
Well-Known Member
I 2nd 67Dart273. I'll add that disk brakes require more line pressure for the same braking. That is why even the smallest cars today come w/ power brakes, i.e. a booster. You may be fine w/ manual brakes if you get an MC w/ a small bore (say 7/8"D) and have a strong leg. Dr Diff sells a kit to install a later aluminum MC w/ small bore (~$100) or rig your own w/ a 2-4 adapter plate ($30 ebay). I used a 99 Breeze ABS MC in my A's. You almost certainly will need a proportioning valve on the rear circuit. If not, your rears will probably skid before the fronts, which is bad (rear-end slides around). Test in a wet parking lot, braking on a turn. You can get an adjustable prop valve (has knob) for $30 or $75 for one w/ an imbalance switch if you want to replace your whole "distribution block".
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