single to dual master cylinder- F/R lines? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

boucher racing · 03-07-2011, 10:59 PM

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.

jimmydean · 03-07-2011, 11:48 PM

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.

**slepysal** · 03-12-2011, 06:45 PM

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

**rideblue00** · 03-12-2011, 09:18 PM

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

**Captainfab** · 03-13-2011, 12:55 AM

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.

Quote:

Originally Posted by rideblue00

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

**rideblue00** · 03-13-2011, 06:44 AM

Quote:

Originally Posted by Captainfab

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.

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?

**Captainfab** · 03-13-2011, 03:48 PM

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

Quote:

Originally Posted by rideblue00

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?

LostMy65 · 02-09-2012, 01:46 PM

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?
Posted via Mobile Device

Rich 5150 69 · 02-09-2012, 01:53 PM

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.

LostMy65 · 02-09-2012, 02:41 PM

Here's pics:

Posted via Mobile Device

losthope · 02-09-2012, 03:09 PM

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

Rich 5150 69 · 02-09-2012, 03:14 PM

OK I

stand corrected....

**jocko** · 02-09-2012, 07:07 PM

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.

**Captainfab** · 02-10-2012, 12:31 AM

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

LostMy65 · 02-10-2012, 03:10 AM

Quote:

Originally Posted by losthope

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

Thanks,

I'll post it here also.

Quote:

Originally Posted by ChiefRocka

The REAR PORT, closest to the PUSHROD is the main, or "primary" chamber.

This port is for the FRONT brakes....

The FRONT PORT, furthest from the PUSHROD is the secondary chamber....supplying the REAR brakes.

03-07-2011, 10:59 PM	#1
boucher racing Registered User Join Date: Feb 2009 Location: Nashville TN Posts: 294	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. __________________ Build Threads: "JED" 66 GMC C1000 http://inliners.org/ubbthreads/ubbth...1857#Post61857 "Cropwell" 66 C10 http://67-72chevytrucks.com/vboard/s...d.php?t=587639

03-07-2011, 11:48 PM	#2
jimmydean Registered User Join Date: May 2005 Location: Beaverton, OR Posts: 3,728	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. __________________ New Project: 1966 LWB C20 Plans: 1/2 ton conversion Dropmember front Dropmember rear Corvette discs Restored raised bed http://67-72chevytrucks.com/vboard/s....php?p=4295210

03-12-2011, 06:45 PM	#3
slepysal Registered User Join Date: Oct 2006 Location: San Jose NOR*CAL Posts: 3,080	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. __________________ 1960 Apache long bed fleet L6 250 Clifford intake 2 bbl carb. Langdon cast headers with dual exhaust and bellflower tips. T-5 5 speed, power steering and power disc brakes. "Over, Around or through it... "

03-12-2011, 09:18 PM	#4
rideblue00 Senior Member Join Date: Feb 2010 Location: Lambertville, MI Posts: 1,865	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.

02-09-2012, 01:53 PM	#9
Rich 5150 69 Registered User Join Date: Nov 2009 Location: Galt, Calif Posts: 2,437	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. __________________ `64 C10 vortec 350/350/373 posi `69 RS/SS 350/350/308 `37 Ford 406/350/324 traclock `68 Dart 370/904/323 suregrip

02-09-2012, 01:46 PM	#8
LostMy65 But Found Her 25yrs Later! Join Date: Oct 2010 Location: Oregon City, Oregon Posts: 10,530	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? Posted via Mobile Device __________________ I lost my 65 - Found it 25 years later: http://67-72chevytrucks.com/vboard/s...d.php?t=426650 66 C20 Service Truck: http://67-72chevytrucks.com/vboard/s...d.php?t=428035

02-09-2012, 02:41 PM	#10
LostMy65 But Found Her 25yrs Later! Join Date: Oct 2010 Location: Oregon City, Oregon Posts: 10,530	Re: single to dual master cylinder- F/R lines? Here's pics: Posted via Mobile Device __________________ I lost my 65 - Found it 25 years later: http://67-72chevytrucks.com/vboard/s...d.php?t=426650 66 C20 Service Truck: http://67-72chevytrucks.com/vboard/s...d.php?t=428035

02-09-2012, 03:09 PM	#11
losthope Registered User Join Date: Apr 2010 Location: sacramento ca. Posts: 1,038	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 __________________ Timmy D. "What that grinding noise?Don't worry about that it will eventually clearance itself!" 1966 chevy c10 Build Thread:http://67-72chevytrucks.com/vboard/s...d.php?t=485977 1954 ford customline H.A.M.B 54 Build Thread:http://www.jalopyjournal.com/forum/s...d.php?t=622142

02-09-2012, 03:14 PM	#12
Rich 5150 69 Registered User Join Date: Nov 2009 Location: Galt, Calif Posts: 2,437	Re: single to dual master cylinder- F/R lines? OK I stand corrected.... __________________ `64 C10 vortec 350/350/373 posi `69 RS/SS 350/350/308 `37 Ford 406/350/324 traclock `68 Dart 370/904/323 suregrip

02-09-2012, 07:07 PM	#13
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,975	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. Last edited by jocko; 02-09-2012 at 07:16 PM.

02-10-2012, 12:31 AM	#14
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,252	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 __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

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