michiganpat
Well-Known Member
I am looking at doing a disc brake conversion over the winter with a suspension rebuild, and does anyone know if the proportioning valve/distribution block is the same between 4 wheel drums and disc/drum?
'73 up brake distribution block/proportioning valve question
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Professor Fate
Push the button, Max...
Different.
michiganpat
Well-Known Member
yeah, figured that out once I cracked open my factory service manual.
Four wheel drums have no proportioning valve.
Hellrats
Just another dumbass
Or you can just put an adjustable valve in the rear line and use a disc/drum master.
michiganpat
Well-Known Member
according to my 1976 FSM, the master cyl is the same between manual drums and manual disc/drum...
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The only difference between them is the sizes of the reservoirs, and early all-drum M/Cs had little hold-back valves in the ports to keep a lil pressure in the lines to prevent seepage of the slave cups.
If you have discs on the front, you have to remove that valve, to prevent the pads from dragging.
On an old Mopar the front discs are plumbed to the rear reservoir.
If you are running bigger tires on the rear than front, I have found rear hydraulic proportioning unnecessary; which can be achieved by varying the slave size, of which there are three to choose from.
The goal of proportioning is to prevent early rear-wheel lock-up, which usually ends up with the backend coming around, and wiping the car out. IMO, having more braking from the rear than the factory provided, is a good thing.
If you have discs on the front, you have to remove that valve, to prevent the pads from dragging.
On an old Mopar the front discs are plumbed to the rear reservoir.
If you are running bigger tires on the rear than front, I have found rear hydraulic proportioning unnecessary; which can be achieved by varying the slave size, of which there are three to choose from.
The goal of proportioning is to prevent early rear-wheel lock-up, which usually ends up with the backend coming around, and wiping the car out. IMO, having more braking from the rear than the factory provided, is a good thing.
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michiganpat
Well-Known Member
right, but my car is not an early car, it's a '76 (build date 11/75), and according to the FSM, the MC the the same for manual brakes whether it's drum/drum or disc/drum.
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Is there an argument in that statement?
I'm just telling you what needs to be.
Early just means before they invented the spring cup energizers for the slaves.
I'm just telling you what needs to be.
Early just means before they invented the spring cup energizers for the slaves.
michiganpat
Well-Known Member
no, I wasn't sure if you were implying that I need to swap the MC in my car, even though I was specifically asking about 73-up in the title
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You can run any M/C that fits.
If the reservoirs are same-sized, then keep an eye on the liquid levels. and
Be sure that whatever one you use, that there is no hold-back valve in the line to the discs.
If the reservoirs are same-sized, then keep an eye on the liquid levels. and
Be sure that whatever one you use, that there is no hold-back valve in the line to the discs.
michiganpat
Well-Known Member
no, mine aren't equal.....MC looks like the power brake one above. looks just like the one listed on rockauto for a '76 duster
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Just another dumbass
Not sure if it took a turn but you really should use the correct parts when doing the conversion. He never asked about a master cylinder so I never said anything about it.
The 1976 model is different from earlier models.
The master cylinder, calipers and proportioning valve were changed in 76. The caliper pistons increased in size which probably required a new master cylinder and proportioning valve.
When doing a drum to disc conversion it would be much easier to find the above mentioned parts from a 73-75 abody. The proportioning valve in 76 was a one year only part.
The master cylinder, calipers and proportioning valve were changed in 76. The caliper pistons increased in size which probably required a new master cylinder and proportioning valve.
When doing a drum to disc conversion it would be much easier to find the above mentioned parts from a 73-75 abody. The proportioning valve in 76 was a one year only part.
I don't see any thign to argue about here.
It was all important info for MichicanPat since it turns out that the car is a '76 model, and '76 has a number of differences that is worth knowing about.
Furthermore, I think its good for @michiganpat to know that the replacement parts from the parts stores are not always correct. Not so much the stores fault as the rebuilders who lump things together that are 'close enough' and that unfortunately includes brakes parts.
@H22A4 Thanks for posting that. Bard's article doesn't fully coiver '75 and '76 A body M/C
I started a cheat sheet for A-body masters a few years ago.
Maybe we could start a new thread and update it with p/n and casting numbers for those years.
Also it looks like they went back to bail tags.
It was all important info for MichicanPat since it turns out that the car is a '76 model, and '76 has a number of differences that is worth knowing about.
Furthermore, I think its good for @michiganpat to know that the replacement parts from the parts stores are not always correct. Not so much the stores fault as the rebuilders who lump things together that are 'close enough' and that unfortunately includes brakes parts.
@H22A4 Thanks for posting that. Bard's article doesn't fully coiver '75 and '76 A body M/C
I started a cheat sheet for A-body masters a few years ago.
Maybe we could start a new thread and update it with p/n and casting numbers for those years.
Also it looks like they went back to bail tags.
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This is written like Richard Ehrenberg writes and just like him, it only tells part of the story.
True, the 4 wheel drum cars do NOT have a proportioning valve but they DO have a distribution block where all the lines converge. To some, they might think these are the same thing.
Telling the story in better detail, one should elaborate by also saying that the distribution block may appear similar, internally it is different and has no proportioning function to it at all.
ajarofclay
Well-Known Member
I'm a little late to the party but this is exactly where I need to be. I have all the hardware for a large disc conversion. My car is a 1972 Demon 340, Manual brakes. There seams to be a lot of knowledge on this thread so my question is Exactly what do I need as far as a proportioning valve and/or Master cylinder change? I'm staying manual and definitely would like to stay away from an adjustable valve. My stock Master chambers are identical which it sounds like many of you know. Thanks in advance for any help...
Hellrats
Just another dumbass
The link for the valve you need is in post #5. You SHOULD change the master system because the reservoir will be larger for the disc brakes. Some will say just keep an eye on it and use what you have but I always change it to the correct one. Silly not to, they don't cost much and by now the one on the car you have maybe 35 plus years old.
ajarofclay
Well-Known Member
Thank you and I do agree, especially going to 12" discs but thought the point about the Master was quite surprising. I'll tell you mine IS the original as I have owned the car since 1974, so... coming up on 52 years old. So all lines and wiring remain the same then, with changing the distribution block to a metering valve? I got some kind of a factory metering valve a while back from a member (attached) but it in NO way adapts. It binds in a distorted angle and and will NOT seat flat using the original bolt hole/frame setup. I'm thinking it is for a B or E body? Again, thanks so much for all the knowledge here; this site Rocks!
Hellrats
Just another dumbass
You may have to change a couple of fittings. I can't remember but I think one is different at the master and maybe one at the valve? Been awhile since i did one. I just cut the line, put on the fitting that I need and make a new flair on the line.
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