Converting from drum to disc brakes

I will be converting from front drum to disc on my 57 chevy truck and instaed of purchasing a double master cylinder through one of the mail order catalogs, I would like to buy one from o'riley auto parts or other local sulpplier. The pricing is much less. Has anyone done this? I will need a double master cylinder for non-power brakes. Part Number? Thanks
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I would suggest getting on O'riley's website and looking up an application that would come stock with this setup. Like maybe a 1974 nova with manual brakes.

 

If you buy a m/c, proportioning valve for an 80 chevy station wagon, even the brake booster, you should be good. Any wagon with a vertical firewall will work and will be a ton cheaper and you will know what to ask for on the road. I even used a chevy sprint brake booster which is pretty small. I hope this helps. Good luck

 

'70s mustang you could get disc/drums without power. '72 Blazer, disc drum no power. Just choose something go to the Oriellys and get them to look it up. Thay are goping to ask you a multitude of stupid questions like Power steeriing, A/C, V8, Disc brakes, power brakes and so on and so forth.

 

This depends on what you plan on doing exactly.
If you want to keep the MC in the same spot, you are going to need to do some fab work as the under floor MCs are just different beasts from the later model firewall mounted units.
If you are going to convert to a firewall mount, are you planning on keeping the original rear drums? Or are you converting to a later style rear drums as well?

The biggest concern would be to maintain the bias of the system.
Usually back in the day, the drums were the same size all around, but the wheel cylinders in the front would be larger to maintain the correct brake bias. You don't want to have too small of a brake caliper/rotor up front compared to the rear or then you would have a rear biased brake system that would take longer to stop than factory.

So if you have 1" rear WCs, and 1-1/8" front WCs with the same 12" drums all around, then upgrading to a disk brake system with 11" or 12" rotors and 70mm calipers(80s Caprice) would keep the bias pretty close. If you are going to stay with manual brakes, a 1" bore should be suffice for the stopping power.

I would avoid any factory combination/prop valves on your truck. The knee point is preset and would not suite your truck correctly. I would just plumb the front brakes directly to the MC, and on the rear install an adjustable prop valve to fine tune the amount of pressure the rear brakes need. This will also be very useful when you are driving with an empty bed or a full load.

Just keep in mind that brakes are a system, you cannot just cobble one together and expect it to stop better because it has rotors.

Centric parts lookup.
http://extranet.soleniuminc.com/centricparts/

www.RockAuto.com is good for looking up the different brands too.

 

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you'll need a pedal mount of some sort, since the original m/c includes the pivot for the pedal....modern master cylinders don't.

original:



Replacement:

 

thanks for the responses. Which type of cover works best for the under floor master cylinder, bolted or the bale type? is there enough clearnce for operating a bale type cover?

 

Depends on how big you make the door in the floor. I have a willwood that I am using on my Stude that has a screw on lid but I got it cheap otherwise I would have used a bale type and just made the door in my floor bigger.

 

For my 49 plymouth, I used a MC for a Mustang 2 with manual brakes - disc front / drums rear. I fabbed a bracket so it could be mounted under my floor and I mounted the pedal on the bracket.

 

Have any pictures of your work? thanks

 

Here is the mock up I did using 1/8" aluminum. The bracket bolts to the original location. The brake pedal moved outboard by about 1/2" and the access hole for the cap was enlarged. There are also links on p15-d24.com of how guys have done this type of thing.