The Stovebolt Site Forums The Shop Area Driveline Master Cylinder Adapter Bracket....

I came across an adapter bracket that lets you upgrade from a single reservoir to a later model dual reservoir for drum brakes. Has anyone done this? What models would fit? Any mods needed for the brake lines? Is there a benefit to using a dual vs a single? I'm keeping the stock drums front and back.
Thanks

It's been awhile, but I think I used a MC from a mid 60's Chevelle or the like. Absolutely,you'll have to do brake line work. You have to separate front and back lines and I think I had to use an adapter on an MC port.And I used a different rod to the brake pedal. Works great though. I bought my MC Bracket from Ghostrider here on the Bolt. Putting that in was the easiest part of the whole changeover.

I've done it. I used a dual master from a 60's full size Chev car (The first year of dual master cylinders. Can't remember the exact year ('66 or '67)) It's fairly straight forward. Your brakes run on two circuits instead of one so if a leak happens in one line, the other line will still work. Safer because you still will have some braking power. Many vendors sell the bracket. Check out Cletis' tech tip here: http://www.stovebolt.com/techtips/master_cylinder/index.html

I asked the same question, can be seen on page 4 with several good responses like yours.
In my area its hard to find a wrecker with cars and trucks from the 60s and 70s, saying that though I'm off right now to a yard I was told about to have a look see, then I could order a new one when I feel satisfied. Seems that most of the jobber parts guys either can't or don't want to suggest an alternative, I get the best ideas at this website, good luck

I put one in my 3/4T. I went to NAPA and asked for the latest drum-drum master from a Chev 3/4 ton. I believe it was for a '72. Works well and is a factory rebuild, rather than a yard find.
I don't mind yard finds, just wanted a little more security with my brakes.

I used a new master from a brake supply house. The counter guy knew exactly what I needed and almost picked one off the shelf without even looking in 'the book'. I wouldn't use a used one.

Does the dual reservoir work better than the single for stopping power?

Stopping power shouldn't change much. Mostly I did mine for peace of mind... With the dual circuit system, a leak in one line doesn't mean an immediate loss of all brakes, just the fronts or the rears but not both.

Do both reservoir's on a dual res MC need to be the same size? I've noticed on different models showing a larger front res for disc and smaller rear for drums. I need new brake lines any how so I'm interested in upgrading to a dual res MC for my drums.

you could look at an old corvette master cyclinder, should bolt up fine. friend of mine used one in a 62 impala worked great

Looking at the Raybestos site, I found a master cylinder for a 1972 C20 (3/4 ton), it mentions its outlet size is 9/16". Wonder if that is the same with yours if you had to use bigger lines or is it just the fitting that is bigger and you would use the stock size with your cylinder. I would guess that for a 3/4 it would be a bigger bore as well?

Just to mention again that if you visit the Raybestos site you can go through all the years for cars and trucks and look at their selection. I like the idea of going to the cylinder used for the 3/4 ton C20 truck the model is MC39075, not sure if bigger lines are required as they mention the outlet size being 9/16in X 18.

If I upgrade to a dual reservoir Master cylinder, will I need a proportioning valve? I figure I'll run a line for the front brakes on 1 port and rear brakes on the other port.

I don't have a proportioning valve and the trucks stops fine. I don't think you need one for a drum drum set up. It's more of an issue if running a disc drum set up.

So I've bolted on the new adapter bracket and dual res master cylinder. When I try to bolt the new eye bolt/push rod to the brake lever arm, it doesn't line up. Seems like the MC is 1/2" too low. Also seems like the push rod going into the MC is too long. Anyone have any problems like this? The master cylinder has a ring holding the main bore plunger in place. I assume the plunger will move deeper into the bore once I remove the ring? That would allow the new push rod to go into it more.
See pic below:

http://s1107.photobucket.com/albums/h394/52ChevyProject/?action=view&current=AdapterBracket.jpg