Master Cylinder Question

I am trying to figure out the brakes for my '56 Buick Wagon. I would like to switch to a more modern 1", dual reservoir master. If I am understanding what I have been told I can use the stock wheel cylinders (1" rears and 1-1/8" front) as long as I have the correct pedal ratio (6:1?) I have been looking on here and Rock Auto to try and find one that will work. It seems that most M/C's have two different sized outlet ports, is this a problem? Do I need to find one with the ports the same size? For example a M/C from a 1973 Buick Apollo (non-power drum brakes) has a bore of 1" but the ports are 1/2" and 9/16", would it work?

I bought a master cylinder at the Portland Swap Meet for $10, turns out it has a 1-1/8" bore and 1/2" and 9/16" ports, if the different port sizes isn't a problem could I use this master if I used a different pedal ratio? If so what pedal ratio?

I am going to frame mount the master cylinder, so I need residual valves right?

Thanks,
Ryland

 

Port sizes not a problem--you can get adapter fittings to fit 3/16 brake line--I just replumbed my coupe.
9/16-18 adapter:Napa# 641-3311--Weatherhead # 7911
1/2-20 adapter:Napa# 641-3305--Weatherhead #7909
Hope this helps you---

 

stick with the 1 inch (mine is). No the the check valves, they are used to keep the pistons in disc applications from retracting.
Drums dont have that problem.
I dislike summit, but they have a M/C in the summer flyer that just arrived.
It is available 1 inch and has a remote reservoir (That will make life alot easier) plus its 66.99
I think I'm gonna switch.

 

Thanks! That is what I thought but I wanted to make sure.

According to this page: http://www.markwilliams.com/calculators.aspx I could use the 1" master with a 6:1 pedal ratio or the 1-1/8" master with a 8:1 ratio and get the same pressure but the difference is that the 8:1 ratio would put ~240lbs more force on the push rod. To me that sounds like I should use the 1" cylinder, do y'all agree?

Thanks,
Ryland

 

yeah 1" master, pedal ratio sounds about right, and you'll need rpv-s in both ends.

I use 74 maverick drum drum masters when I do a conversion. Last 2 have had rpv built in. (dunno why but they were there)

 

Thanks Darrin, I will buy a 1" M/C. Could you send me a link to the one you are talking about? I can't seem to find it on their website. If I do a frame mount and put an access door right above the master is it still beneficial to get a remote reservoir? The '73 Apollo one is $35 with shipping so considerably cheaper.

Thanks,
Ryland

 

I think the 1" bore will be fine as long as you use a manual brakes pedal assembly, which it sounds like you will.


I thought you always needed residual valves with a frame mount MC, are they built in to the MC or something?

http://www.mbmbrakeboosters.com/F.A.Q.-S/FAQs-Proportioning-Valves.html

edit: from that website's Troubleshooting Guide-really excellent stuff!

Residual Check Valves - These valves are used to hold a certain amount of pressure in the lines even when the pedal is not pressed. This is a sort of preloaded line pressure to activate the
brakes more quickly. They will give a higher, harder and more responsive pedal. Residual check valves should not be used as a substitute for a properly functioning system.
For instance, do not use residual check valves in place of complete and proper bleeding procedures as presented in this guide and our Brake Bleeding Guide.
Check valves will most likely be necessary when the master cylinder is lower than the calipers or hard lines run higher than the master cylinder fluid level.
In disc brakes a 2 lb. residual check valve prevents fluid from flowing back without causing the brakes to drag. With drum brakes, a 10 lb. valve is used to
compensate for return spring tension in the drums. Residual check valves are generally color coded blue for 2 lb. and red for 10 lb. for easy identification.

 

My M/C is foreword of the brake pedal, and I did build a little door to access it.
However, getting to the M/C still is a pain, OK, maybe a nuisance.
The remote fill would make my life easier.
If your pedal runs towards the back of the car, and the reservoir is under the flat part of the floor I would buy the $35 dollar one.
I'm still not behind the check valves on a 4 drum car...But, I may be wrong
They have been stopping for 54 years without 'em.
...also it was a Wilwood/Jegs part #950-260-3378

 

Darrin: Thanks again! I read somewhere that most drum/drum master cylinders have a sort of check valve built in, that could be why you haven't needed one. In my shop manual it says the my Buick came stock with two.

Thanks,
Ryland