47-55.1 Master Cylinder/Booster HELP!!

[NeoJuice]

Hello fellow forum members,

I really hit a road block yesterday when it comes to my brakes and I need some help with what to do with my master cylinder/booster in my truck. I was getting ready to plum all my break lines and thought I would pull out the MC/Booster last night to bench bleed it before getting started.

As some of you might know I purchased this truck from a guy who started the build but lost interest and I wanted to make sure I had the correct unit in the truck for my disc/disc setup.

Here is the link to my build thread just in case along with pictures of my rear disc setup on the last page.

http://67-72chevytrucks.com/vboard/s...d.php?t=723325

I finally got in all my break parts like copper/nickle break line & all my fittings organized to start the job. I also got in my flaring tool from eastwood tools & 2lb residual valves, 3 way splitters & frame clips so I was totally ready to start the job.

The only part I havent figured out yet is what I was also going use for a proportioning valve. I was thinking about using this one from wilwood because it also has a built in brake switch.

http://wilwood.com/MasterCylinders/M...emno=260-11179

Ok so here is the problem. The MC/Booster he put in the truck was for as far as I can tell for Disc/Drum setup. On the MC/Booster the only informaiton I can find is on the rubber plunger it says MBM and then on the bracket MBMPRAFMCT4754.





So looking up MBMPRAFMCT4754 on the MBM site says that its the frame bracket but it also lists all the MC/Boosters being only disc/drum or drum/drum.

http://mbmbrakes.com/search.php?Sear...MBMPRAFMCT4754

So what do I do now? Can I just replace the master cylinder and keep the booster? Should I call MBM and see what they say? Also I noticed when i tried to push in the rod on the booster it wouldnt move in/out. Is that because there is no vacuum or fluid in the booster? looking at the fluid bowls i believe the front one was larger then the rear if I recall correctly.

Or I could just be freaking out over nothing and it has this MC on it but i would need to find a stamping of some sort or model number.

http://mbmbrakes.com/mc2912h-gm-univ...er-1-1-8-bore/

Or scap it for a underhood booster/pedal assembly?

Thank you for your help and time.

[OrrieG]

I do not think the booster makes any difference but you will need a disc/disc MC. I think most kits use a GM one for earlier Corvettes. You can tell because the reservoirs and outlet fitting are the same size. Ideally the MC is mated to the correct calipers so the fluid volume being pumped is correct. I would start with IDing the calipers and make sure the MC is correct.

[NeoJuice]

Front end is TCI Mustang II and the rear calipers are 1980 Cadillac Seville.

If you look at the second image on the MBM link below I believe the front reservoir is larger like in the picture. Now I just need to find a stamping of what MC it is. I'm going to try and phone MBM today and find out

http://mbmbrakes.com/mc2912h-gm-univ...er-1-1-8-bore/

[dwcsr]

I see you have the clevis in the wrong hole or the brake arm , It goes into the other one, The part number is for the bracket only, its for 55-59 trucks, the booster is universal works with almost any master, The master you need is for disc/disc so just get a master

the wildwood prop valve works well on these systems

[Rude Dude]

The booster doesn't have a thing to do except use vacuum to aide in the pressing of plunger in M/C. Your master cylinder looks like corvette style so the determination weather it is disc/drum or disc/disc would be in the proportioning valve and I noticed you do not have one on.

[NeoJuice]

I called MBM today and to say the gentlemen I talked to was quite rude. But from the little bit of information I could get out of him was this.

- did it have two ports or four. I said it had four ports so he said that is not a disc disc MC and would need one with ports.
- I would need two 2lb valves which I have and a MBM PV4 proportioning valve. I think I might go with the wilwood instead.
- the master cylinder I have he said is a 1" bore and I need 1 1/8" bore.

That's about all the information I got out of him. I'm going to try and see if I can get there GM one. But I will update the post later when I have more information.

Hopefully this one will swap onto the booster.

http://mbmbrakes.com/mc2912h-gm-univ...er-1-1-8-bore/

[NeoJuice]

Originally Posted by dwcsr

I see you have the clevis in the wrong hole or the brake arm , It goes into the other one, The part number is for the bracket only, its for 55-59 trucks, the booster is universal works with almost any master, The master you need is for disc/disc so just get a master

the wildwood prop valve works well on these systems

In the picture the brake pedal is not connected to the booster plunger arm it's just sitting there. Is there any reason why I can't move the plunger in/out? Could it be seased? Or does it need to be under vacuum to work?

[NeoJuice]

Originally Posted by Rude Dude

The booster doesn't have a thing to do except use vacuum to aide in the pressing of plunger in M/C. Your master cylinder looks like corvette style so the determination weather it is disc/drum or disc/disc would be in the proportioning valve and I noticed you do not have one on.

I think I'm going with the wilwood one. That's why there is nothing there. I'm basically building the brake system from scratch.

[dsraven]

you may have better luck bleeding the master if you simply take the master off the booster, clamp it in a vice or workmate or whatever, then put a short brake tube from each outlet into the res for each corresponding circuit. they sell brake master cyl bleed kits with universal sized plastic fittings and clear hose if you have a couple of extra toonies. that way you can see the fluid in the hose as you bleed. fill the master then pump the piston in and out slowly, making sure the tube ends stay submursed in fluid inside the res, until there are no more bubbles coming through. pull the plastic tubes out of the res, plug them, then cap the res and install the master back on the previously mounted booster. connect the lines from the master to the system right away to ensure there is no fluid lost or air allowed to get into the system. then bleed the system asap for the same reason.
of course before you do all that you will need to source a master set up for disc/disc. it may come with the bleeder kit i mentioned, most do. if you find out what master you need you could try napa etc for a new one at Canadian prices, or try a place that specializes in corvette. like western corvette in Calgary., not sure what is available in Edmonton. just a thought. also, once you have the new master in hand, ensure to check the pushrod hole depth compared to the master you started with. it is critical to have some play in the booster pushrod to master cyl piston fit relationship but you don't want too much either or you lose pedal travel to take up the slack. ensure the booster is also working correctly. cars with power brakes usually had larger bore masters because the booster assisted the greater pedal effort required for a larger master bore compared to manual brakes.

[dsraven]

I know the write up on the master in your link says disc brake conversion and also disc/disc but the application chart is for cars that came with disc/drum. unless it has been modified internally? how about if you check a master for a car that comes with disc/disc. like a 70's corvette. check online for mounting flange specs and piston pushrod bore depth. i think the manual versus power brake difference is the depth of the pushrod bore in the piston as well as possibly the bore size of the master cyl. that way availability would be better if you ned parts down the road and you know for sure it is for disc/disc plus year and model of donor car. pushrod bore adapters are available.
1977-82 corvette 350 auto master cyl in stock at my Napa store calgary
Part: NUP 39052
list price $112.42
# of Line Ports : 2
Brake Master Cylinder Bore Size : 1 1/8 in.
Brake Master Cylinder Line Thread Size : (1) 1/2 in. - 20 And (1) 9/16 in. - 18
Warranty

[NeoJuice]

DSRaven as I said before you are a wealth of great knowledge and I thank you for your help.

I had some time to tinker in the garage last night and I pulled the MC off the booster. After removing the MC from the booster I was able to pump the piston in and out slowly with the piston adapter in place. The problem with this whole setup is that there are no markings on the MC at all. Here are some updated pictures.

The bore size looks to be about 1 1/16". So I'm not sure what this MC could be off of. You can see the front bowl is larger then the rear. Just because it has 4 ports on teh MC doesnt mean it could not be disc/disc.

I will look into the corvette MC.

[dsraven]

the masters with 4 ports can be blocked on one side I believe, like yours is. I would call napa or parts source, auto value etc and see if someone has a corvette one in stock. then go and compare. sell yours on kijiji or whatever. that way you know it is a disc/disc for sure and also know exactly what it came from.
maybe the camera angle but yours looks more like 1" bore from the pic.

[dsraven]

your master may be from a disc/disc set up and the rear calipers are a smaller displacement due to brake bias and less requirement for brakes on the rear than on the front-so smaller res on the rear-I dunno for sure. compare to corvette because some corvette cyls had 4 ports.

[dsraven]

the front and rear brakes on the eldorado from 77 have an 11" brake rotor and a 1 1/8 bore master cyl. it looks a lot like the corvette or like your cyl except a taller res. you can check it out online at napaprolink.ca or stop in for an eyeball check. what diameter are your front brake rotors?

[NeoJuice]

Originally Posted by dsraven

the front and rear brakes on the eldorado from 77 have an 11" brake rotor and a 1 1/8 bore master cyl. it looks a lot like the corvette or like your cyl except a taller res. you can check it out online at napaprolink.ca or stop in for an eyeball check. what diameter are your front brake rotors?

Rear end is a 1980 Pontiac Trans Am w/rear disc brakes. From what I can find online rear rotors are 11.16. I picked those up from bumper to bumper.

The front end is TCI mustang II front end and I would need to measure the rotors for the correct size. There website install instructions say they could be
4.75” Bolt circle 10.5” rotors = 12mmx1.5(’82-’87 Camaro)
4.75” Bolt circle 11” rotors = 7/16”x20(’75-’80 Granada redrilled)

If I picked up a corvette MC will it bolt up to this booster? MBM website says its a 7" Dual Diaphragm Booster if it is truely a PBUFMCT4754 setup.

[dsraven]

sorry, I thought I read you had an eldorado rear disc set up.same size rotors anyway.
I don't know for sure if the corvette master would bolt up ,but a lot of chevy stuff has the same pattern. see if they have one in stock and compare I guess.

[59chev]

I have the CPP kit based on the corvette master that i purchased from KMS tools. According to them the Master is identical in a disc - disc or disc-drum situation, the only difference is the proportioning valve. My holes on one side are blocked. I believe the extra set of holes allow more flexibility to swap the lines over to the other side for certain applications.

[NeoJuice]

Originally Posted by 59chev

I have the CPP kit based on the corvette master that i purchased from KMS tools. According to them the Master is identical in a disc - disc or disc-drum situation, the only difference is the proportioning valve. My holes on one side are blocked. I believe the extra set of holes allow more flexibility to swap the lines over to the other side for certain applications.

59Chev,

That's interesting that you say that about your MC/Booster. I guess I could just put it back together and see what happens. Do you have any pictures of your setup I could look at? Do you have a link to the CPP website with the part number?

What proportioning valve are you using? I was thinking about using the wilwood one because it also has a break light switch in it. I'm sure it's not going to be cheap but I think the MBM PV4 wont be either. Or I go to the wreckers and pull one off another vehicle.

Looks like Photobucket changed there hosting. Now all the images are broken probably for every thread on this forum LOL.

[NeoJuice]

Originally Posted by dsraven

sorry, I thought I read you had an eldorado rear disc set up.same size rotors anyway.
I don't know for sure if the corvette master would bolt up ,but a lot of chevy stuff has the same pattern. see if they have one in stock and compare I guess.

See what 59chev said below. My MC has a larger front bowl then the rear just like the corvette style/GM universal one.

Like I said below, i can put it back together get everything plummed and if it doesnt work properly swap it out for a corvette MC instead. what about the bore size being like 1-1/16" ?

[59chev]

Here is the kit that I have:

http://www.classicperform.com/Store/...ks/4754BBD.htm

[NeoJuice]

Originally Posted by 59chev

Here is the kit that I have:

http://www.classicperform.com/Store/...ks/4754BBD.htm

Thanks for the link. And is yours under floot mount or under hood? and I'm assuming your using the proportioning valve from the kit.

[59chev]

Mine mounts under the floor, using the original pedal. When I purchased it, they had a bunch of the disc-disc kits on sale, and just sold me the disc-drum proportioning block separately. They said the kits where identical except for the proportioning block and all I needed to do was swap it out for a disc-drum application.

[NeoJuice]

Originally Posted by 59chev

Mine mounts under the floor, using the original pedal. When I purchased it, they had a bunch of the disc-disc kits on sale, and just sold me the disc-drum proportioning block separately. They said the kits where identical except for the proportioning block and all I needed to do was swap it out for a disc-drum application.

Do you still have the disc disc proportioning valve? Could save me $125 bucks on the wilwood one.

[NeoJuice]

Is it necessary in every application to have the Adjustable Proportioning Valve plummed into the system? or can you just get away with a standard proportioning valve like the PV-4

[NeoJuice]

So I just talked with a guy and he said I should be fine. He said to re-install the MC and get the wilwood proportioning valve and put in my 2lb residual valves in the front/rear and everything should be good. Plum the larger front bowl to the front brakes and the smaller bowl to the rear brakes.

Anyone have any other thoughts? crossing my fingers everything works out ok.