single to dual master cylinder- F/R lines?
 

I just swapped out my single master cylinder for a double and split the lines. I am pleased the way it turned out, but got to thinking. The M/C is for a drum/drum setup, so the front and rear reservoirs are the same size. Does it matter which line goes to Front or Rear? Right now I have the line closest to the firewall going to the rear.
https://lh5.googleusercontent.com/_6...elinesdone.jpg

Re: single to dual master cylinder- F/R lines?
 

As far as I know it doesn't matter if you are running drum/drum. But you will need a proportioning valve for disc/drum and then it matters what hole on the prop valve you use.

Good looking install.

Re: single to dual master cylinder- F/R lines?
 

ON mine I used the rear port for the rear brakes and the front port for the front brakes.

Re: single to dual master cylinder- F/R lines?
 

How did you decide what master cylinder to buy? Or what was it from? It looks like it fits well.

Re: single to dual master cylinder- F/R lines?
 

If you're running drum/drum brakes, get one for a '67-'70 pickup. If you're running disc/drum brakes, get one for a '71-'87 pickup as well as the correct proportioning valve.

Re: single to dual master cylinder- F/R lines?
 

So i am assuming that 67-70 is the drum/drum still? Because i know some of the 67-72 years had disc brakes. 71-72?

Re: single to dual master cylinder- F/R lines?
 

Yes, the '67-'70's were only available with drum/drum brakes, Front disc brakes weren't available until '71

Re: single to dual master cylinder- F/R lines?
 

The master cylinder I pulled off the 1/2 ton 79 suburban had disc/drum, but the front and rear reservoirs are the same size. I thought disc/drum reservoirs were supposed to be different sizes. Beings they are the same size, would I be able to use it on my 65 drum/drum?
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Re: single to dual master cylinder- F/R lines?
 

Then someone had the wrong master on the suburban, you can use the disc /drum on a drum/drum if you choose to make a change to disc at a later date.

Re: single to dual master cylinder- F/R lines?
 

Here's pics:
http://i1106.photobucket.com/albums/...5/IMAG0800.jpg
http://i1106.photobucket.com/albums/...5/IMAG0799.jpg
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Re: single to dual master cylinder- F/R lines?
 

IF YOU GOTO POST #80 ON THIS LINK IM POSTING THAT "CHEIFROCKA" DID ON DUAL MASTER SPLITING LINES ON A DRUM/DRUM HAS A PICTURE SAYING THE RESERVOIR CLOSET TO THE FIRE WALL IS FOR THE FRONT BRAKES!!
http://67-72chevytrucks.com/vboard/s...d.php?t=332148

Re: single to dual master cylinder- F/R lines?
 

OK I :but::dum::agree: stand corrected....:lol:

Re: single to dual master cylinder- F/R lines?
 

Hey, back to the original question - on a drum/drum dual reservoir master cylinder - YES, it DOES matter which reservoir goes to front/rear brakes, and it is less than obvious. The FORWARD reservoir's port (closest to the grille) should be connected to the rear brake line. The aft reservoir's port (closest to the firewall) should be connected to the front brake line. The reason for this is that a dual res drum/drum master does "pseudo" proportioning in the way the ports are uncovered when the master's piston slides forward (when you press the brake pedal). So, it is important - if you do it backwards (as suggested in some of the above posts), you will have pressure to the rear brakes first and potentially lock up the rears only in a panic stop. Not good. This is also why there is no need for a prop valve on a drum/drum setup (yes, a brake pressure transducer can be placed in between the lines, but not a true prop valve on a drum/drum setup).

67 dual drum master is a great sub for the old single master, gives you a much safer system. someone mentioned Chief Rocka's thread above - agree, great thread.

Here's the line split I did a while back:
http://67-72chevytrucks.com/vboard/s...d.php?t=487384

EDIT - Hey, Losthope - I'm sorry, somehow I missed your post - you answered this spot on.

Re: single to dual master cylinder- F/R lines?
 

I have seen a number of master cylinders on disc/drum trucks that had both reserviors the same size. I think it must have to do with the particular brake option/package that the truck came with. In my experience it has been more common on C20's

Re: single to dual master cylinder- F/R lines?
 

Thanks,

I'll post it here also.