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Upgrading master cylinder

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I see a bunch of topics about upgrading to a dual reservoir master cylinder for a 47 Dodge WC.  Most recommend a 1992 Toyota Celica master cylinder.  It has the same bolt pattern and is relatively cheap.  I have also seen reference to a proportioning valve.  It appears there is no generic one.  There are a lot of variations.  Has anyone done this and what proportioning valve would you recommend.  I still have my original drum brake set up.   How would I plumb this.  Based on what I read it looks like I would install it between the master cylinder and the line feeding the back brakes but some I have looked at also go between the master cylinder and front brakes so it can adjust to demand.  I am thinking that is too complicated for our simple set up? Any feedback is appreciated.  I keep putting this off.  I have a brand-new master cylinder but for safety reason I just keep thinking about crashing my truck because of a leaking brake line disabling the entire brake system. 

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In the past I have asked a similar question. Do we need a proportioning valve for this conversion?

I think the general consensus is .... no, if you are running drum brakes all the way around. Yes, if you convert to disk brakes.


Further discussions on it, some of the older MC have a proportioning valve built in ..... The Toyota may be one of them ... I have no proof it is.

The only importance to that is ..... The Toyota MC has a single bowl feeding both front & rear .... so I do not know which line should feed front or rear.

Or even if it matters? ..... I figure if my rear brakes work harder or lock up before the front, then I will switch the lines around.


Others who have done the conversion using stock drum brakes are happy with it.

I did the same thing with no proportioning valve installed .... they seem to work fine but have not yet driven it on the road.

One problem I ran into was the MC is 10mm threads for the lines, I have 1/4" lines. I had to order a adapter to go from 10mm > 3/16" then another adapter from 3/16">1/4"



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I've done it using the Toyo master, but did disk brakes up front and drums in the rear. I used a PV2 proportioning valve, and also added residual valves. I added the residual valves because I'm not really happy with how it all is working. There is a lot of pedal travel for one, and the rear brakes don't lock hard.


I'm planning on swapping in a Dodge master cylinder in the near future, and just adapting it to the mounting locations. That will also answer the question of which is front and which is rear the Los brought up. Don't know which one yet, but something dual circuit and no power brakes. I'll do a thread when I get to that. I'm hoping it will make my brakes work more like they should. Having the wrong size bore in your master cylinder leads to either too much pedal effort of too long of a travel. Maybe to the point of having to pump the brake pedal more than once.

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I had low pedal the first time I bled my brakes.

A:, I never properly bench bled the MC.

B:, I never properly adjusted the brake shoes ..... I always first get hydraulic pressure to set them in place .... then adjust.

C:, Turns out I had a small leak from improper fittings ..... So I ordered/installed correct fittings. ..... While I had brakes that needed adjusting, I let it sit for a month and had none because of the fittings.


I'm only suggesting that I never heard of complaints with low pedal from the swap .... I have it but blame it 100% on me.

I fully expect to have decent pedal the next time I bleed the brakes .... I have corrected all my mistakes except bench bleeding it.

I feel if it is needed I can do it while installed on  a under floor MC.


@lostvikingare you certain you have done everything correct? I know from past experience a firewall mounted MC is impossible to get bled properly once mounted.

Not sure why I think I can do it fine in my under the floor system ...... You can never get the proper throw from a brake pedal rod to purge the air from a MC .... you need to disconnect the brake pedal & manually push in the cylinder ..... very easy on a bench, tough when installed. ..... I have installed a new MC on my 1969 mustang and never got good pedal from it. ..... Until I removed it, bench bled it and re-installed it.


Properly installed I have not heard of complaints from others about low pedal ..... yes I have it, but totally my fault.

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I have zero leaks, because all the fittings were correct and the flares were textbook. I have a pressure bleeder, so that isn't an issue either. I've repeated the bleeding a couple times. I do get a firm pedal, but it's much longer of a push that I believe it should be, in fact a partial push and release with a quick second push put the pedal near the top. Changing the bore diameter of a master cylinder is well known to affect these things. It's a simple matter of PSI and volume.


Other than the similar flange, I don't really like the Toyo master. I prefer a nice cast metal master with two separate chambers for fluid. Unless someone used the same 95 Jeep Cherokee rear, to get the same wheel cylinders, and used the same Scarebird conversion (and same calipers), the results are apples and oranges.



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I just ordered this master cylinder,



It's for disk/drum on a 1975 Dodge Dart. It has a four bolt mount, so I'm going to build a .250 thick plate of steel and adapt the stock three bolt to that. I'll use some flathead screws to secure the plate to the truck, and put four flathead screws into the plate, facing the master to act as studs. I'll weld the heads in place to keep them from turning.


I'll let you know how it goes.

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  • 3 weeks later...

Before anyone else makes the same mistake. I tried fitting that master cylinder in the truck today, but there just isn't enough room. It's longer than the stock one was, so it hits the steering box, and it might hit the starter also, I just couldn't tell. Bummer.


I'll keep it and give it a try if I get an IFS installed some day.

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I just did a Rusty Hope disc brake conversion on my B2B. I decided it was a good time to do a dual reservoir swap also. Rusty Hope recommended the ‘86-‘88 Toyota Celica MC. It’s a three bolt pattern just like stock. The holes just needed to be hogged out a little. No need for an adapter plate, which can take up valuable space. My research told me there is no need for a proportioning valve with an all drum setup. The proportioning valve is for a disc-drum or disc-disc setup. I used a Wilwood adjustable valve. You also need a 2lb. residual pressure valve for the disc brakes and a 10lb. for the drums. I used Wilwood valves. They need to be installed as close to the MC as possible. I fabricated a bracket to mount the proportioning valve next to the MC. I also installed a metering valve for the disc brakes. Some refer to this as a “hold-off” valve. It prevents the disc brakes from being applied under light braking (low line pressure). My guides in all this were several hot rod books, but mainly “The Street Rodder’s Handbook” by HP Books. Hope this helps. BTW, my truck stops instantly. What a difference…

Edited by Jim Shepard
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Other than using a Scarebird kit, that is exactly what several of us have done and documented in thread here. I added the Wilwood residual valves later, but I'm sure we are using the same parts. I also didn't come up with the Toyo master, another person who had already documented it supplied that for me. I'm back to that right now btw. Funny thing is, every time I've had the lines off and master dry, I've been able to fill it up and wait over night...then just pump. Never had to bench bleed the master :)

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