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Username Post: Single to dual master cyl.        (Topic#368529)
PtownBubba 
Member
Posts: 38

Age: 71
Loc: Illinois
Reg: 07-30-06
05-27-22 01:19 PM - Post#2841927    

I have a 1957 Chevy BelAir hardtop. 6cyl. It has the single non-power brake master cylinder. Is there a 'kit' available to convert a single to a dual non-powered ? All 4 drum brakes

Bubba and Kathy
Illinois


Edited by PtownBubba on 05-27-22 01:23 PM. Reason for edit: No reason given.

 


55MAS 
Senior Member
Posts: 1633

Loc: North Coast, USA
Reg: 12-19-01
05-27-22 05:05 PM - Post#2841930    
    In response to PtownBubba

Back when I did that I used a MC for a '68 Pontiac Lemans with non-power 4-wheel drums. I used it because I had it. Approximately the same weight and worked well. Any midsize GM product would be similar. Probably could buy one at a NAPA or other regular automotive parts store. You will also need to revise the brake lines a little for the new 2-oulet MC. Refer to a GM service manual if a diagram is needed.



 
rls8836 
Member
Posts: 428

Loc: North La.
Reg: 01-30-02
05-28-22 06:19 PM - Post#2841966    
    In response to 55MAS

55XMAS could you expound a little more about the brake lines. I have a 55 in the same shape with single master cylinder and have considered swapping to the double. Thank you



 
Bad56Sedan 
"15th Year" Gold Supporting Member
Posts: 1516
Bad56Sedan
Loc: Pasadena, Texas
Reg: 04-29-04
05-28-22 08:55 PM - Post#2841971    
    In response to rls8836

well, there is even more to that story,
what you find is the stationary bolts in the firewall are too short because the master cylinder you are putting on is thicker at the mounting surface than the original.
https://chevytalk.org/fusionbb/showpost.php?post/2...
This post explains the joys of removing or replacing the too shorts stock bolts
The replacement bolt is grade 8, 3/8" fine thread x 2".
Shoulder bolt is best, the ones i bought were 3/4" shoulder.
Yes you can try the hammer method to drive/ pop the TOO short bolts out.
The original bolts are pressed into the main brake pedal bracket, may even be hot pressed. They are mechanically hit so the shoulder expands, the dimple in the head, I guess.
I put liquid wrench, wd 40, the other stuff and then that stuff on the bolts for a few days.
No way, I had hit the bolt so hard it did not budge, it bent the crap out of the main brace under the dash, messed the bolt end up.
Used small cutting disc to true end of bolt, center punched and drilled out.
Push the new bolts through under the dash, carefully put MC on the bolts hand start nuts.
Then under the dash position 1/2" wrench over the head of one bolt, one side you can brace the wrench on the main bracket, other side i actually tied the wrench to the main brace.
It worked .
This method is the best, Cut off flush with firewall then enter punch, and drill, as mentioned.
but you were asking about the brake lines?

VC56S 2 door Sedan, 41 Years


 
schudaddie 
Senior Member
Posts: 319

Loc: SW, MI
Reg: 10-31-01
05-30-22 04:58 AM - Post#2842020    
    In response to PtownBubba

here ya go.....
https://store.fillingstation.com/detail/DB-103/Che...
later, bill



 
PtownBubba 
Member
Posts: 38

Age: 71
Loc: Illinois
Reg: 07-30-06
05-31-22 12:05 PM - Post#2842088    
    In response to schudaddie

So,,,, If I replace the old single mc, to a dual,,,, the firewall bolts are too short .

This dual MC ----listed above----- says it is for a disc/drum setup,,, I have all 4 drums,,,
Is there a dual mc out there that will bolt on original fire wall bolts.????
Finally the dumb question,, it seems with 'any' dual mc,, you must use the 'prop' valve,,,,,???? My single mc has 'no' prop valve now,,,, why do I have to have a prop valve with a dual mc ????? Right now all 4 of my drums feel the same push,,, what changes with a dual mc,, why can't there be one that pushes all 4 drums the same,,, like I have now ???? Sorry for the dumb question,,,,


Bubba and Kathy
Illinois


Edited by PtownBubba on 05-31-22 12:07 PM. Reason for edit: No reason given.

 
Shepherd 
Valued Contributor
Posts: 2583

Loc: Lake George, NY
Reg: 11-11-15
05-31-22 01:19 PM - Post#2842091    
    In response to PtownBubba

No prop valve with 4w drums, just split ft and rear circuits. I would use a dual master for 4w drums, though.



Edited by Shepherd on 05-31-22 01:21 PM. Reason for edit: No reason given.

 
PtownBubba 
Member
Posts: 38

Age: 71
Loc: Illinois
Reg: 07-30-06
05-31-22 02:53 PM - Post#2842095    
    In response to Shepherd

An all wheel brake drum,,, Master Cylinder for a 57, is not easy to find,, I believe this is what I need,,, then will have to make a grocery list of lines and fittings I will need,,,,Linkhttps://www.ebay.com/itm/232634017180

Bubba and Kathy
Illinois


Edited by PtownBubba on 05-31-22 03:55 PM. Reason for edit: No reason given.

 
55MAS 
Senior Member
Posts: 1633

Loc: North Coast, USA
Reg: 12-19-01
06-01-22 05:17 AM - Post#2842134    
    In response to PtownBubba

  • PtownBubba Said:
An all wheel brake drum,,, Master Cylinder for a 57, is not easy to find,, I believe this is what I need,,, then will have to make a grocery list of lines and fittings I will need,,,,Linkhttps://www.ebay.com/itm/232634017180



See post for for an appropriate non-power 4-wheel MC factory GM application that bolts on. Later model MC will only use the 2 lower fasteners.

You could use the factory splitter valve for the same application - it has a switch to trigger a brake warning light. But is is is not a proportioning valve.

As pointed out above - do not pound out the studs - they are welded and must be drilled out. When I did mine long ago I drilled and tapped for a 3/8 screw as original. There is enough meat in the stud head to mage the threads. Then install screws from inside. I also removed the entire brace to work on it on the bench. I have seen some MC where the flange thickness is the same as the =55=57 and do not require longer studs.




 
PtownBubba 
Member
Posts: 38

Age: 71
Loc: Illinois
Reg: 07-30-06
06-01-22 06:04 AM - Post#2842136    
    In response to 55MAS

I saw the post above for the mc,, clicked the link,,,,it is described as ad Disc/Drum mc,,,, I took that to mean front disc rear drums,, not disc or drum brakes,,,,,,The Ebay one, says 4 drums,,, and does not mention anything about having to drill and install new bolts,,,,,,,,,,,,,,,,and says nothing about using it with any type of valve,,,,,so,,,,,,, will the Ebay one work

Bubba and Kathy
Illinois


 
55MAS 
Senior Member
Posts: 1633

Loc: North Coast, USA
Reg: 12-19-01
06-01-22 01:10 PM - Post#2842149    
    In response to PtownBubba

Sorry - I meant to say see my post, #2, where I mentioned the 4-wheel drum GTO MC. You could get that at the corner store. Look and touch before you buy.



 
PtownBubba 
Member
Posts: 38

Age: 71
Loc: Illinois
Reg: 07-30-06
06-01-22 07:19 PM - Post#2842180    
    In response to 55MAS

I ordered the Ebay MC,,,,I asked about special mounting, and prop. valve,, he simply said this
  • Quote:
yes it bolts right up . it does not require a proportioning valve for drum brakes but you can put one in if you like



So now i need to plumb it up,,

Bubba and Kathy
Illinois


 
PtownBubba 
Member
Posts: 38

Age: 71
Loc: Illinois
Reg: 07-30-06
06-02-22 10:16 AM - Post#2842205    
    In response to PtownBubba

Well, crap,, I just now noticed my old Single MC is a 4 stud mount,,,,ugh,,,,,

Bubba and Kathy
Illinois


 
japete92 
"8th Year" Silver Supporting Member
Posts: 2018
japete92
Loc: No. Virginia
Reg: 01-18-13
06-02-22 03:21 PM - Post#2842222    
    In response to PtownBubba

If the cylinder is for disc/drum systems (not specifically for an all drum system) is likely does not have built in residual pressure valves (one for each line). Why? Because the drum brakes require approx 10 psi residual pressure and the disc something closer to 2 or 3.

There are external residual pressure valves available. One goes in each line (feeding the separate front and rear 'systems').

The all drums systems require equal hydraulic pressure thru-out the entire system. The approx 60/40 front/rear braking force distribution is attained via wider drums and shoes in the front. There is also a slight difference in the wheel cylinders.

Proportioning valves are how the drum/disc combo systems allow proper function (differing hydraulic pressure front/rear). If one was used in an all drum system it would have to be adjustable AND adjusted to supply equal pressure (front/rear). Superfluous.

Just some info.

Pete



 
PtownBubba 
Member
Posts: 38

Age: 71
Loc: Illinois
Reg: 07-30-06
06-02-22 08:54 PM - Post#2842237    
    In response to japete92

I asked my seller about the 2 bolt mount, of new dual mc, since my old single is a 4 bolt,,, he said no problem,,the 2 bolt will work fine. And he added,, I did not 'need' a prop valve, or any valve,,, so,, I guess it just makes the all in one system, a front back system,,,,,


Bubba and Kathy
Illinois


 
Rick_L 
Member #409
Posts: 27986
Rick_L
Loc: Katy, Tx, USA
Reg: 07-06-00
06-03-22 07:46 AM - Post#2842247    
    In response to PtownBubba

You won't find any 4 bolt master cylinders in the dual reservoir style anyway.



 
japete92 
"8th Year" Silver Supporting Member
Posts: 2018
japete92
Loc: No. Virginia
Reg: 01-18-13
06-03-22 07:48 AM - Post#2842248    
    In response to PtownBubba

  • PtownBubba Said:
I asked my seller about the 2 bolt mount, of new dual mc, since my old single is a 4 bolt,,, he said no problem,,the 2 bolt will work fine. And he added,, I did not 'need' a prop valve, or any valve,,, so,, I guess it just makes the all in one system, a front back system,,,,,





I do not know what you mean by '...all in one system, a front back system...'.

BUT the front reservoir connects to the front brakes and the rear reservoir connects to the rear brakes; creating two totally separate hydraulic runs. If one fails the other is intact. Partial emergency braking is retained.

You WILL have to re-plum your hydraulic brake lines to create the separate systems.

The one 'pot' master cylinder has only one hydraulic line exiting from it. It goes to a 'T' and then to the front and rear brakes via separate hydraulic lines. Any loss of pressure at any point in the system becomes a loss of pressure in the entire system.

Recommend you do some independent research on the function/necessity of the residual pressure valves in the all drum systems. IF the master cylinder does not have them built in, external ones are required. One for each 'system'.

Your car, your money, your choices.

Pete





 
55MAS 
Senior Member
Posts: 1633

Loc: North Coast, USA
Reg: 12-19-01
06-03-22 07:57 AM - Post#2842249    
    In response to PtownBubba

  • PtownBubba Said:
I asked my seller about the 2 bolt mount, of new dual mc, since my old single is a 4 bolt,,, he said no problem,,the 2 bolt will work fine. And he added,, I did not 'need' a prop valve, or any valve,,, so,, I guess it just makes the all in one system, a front back system,,,,,





I guess you didn't read my post on 06-01-22 08:17 AM - Post#2842134.
I pointed out that only the bottom 2 fasteners are used.
As RickL said no 4-hole flanged dual MC.





 
PtownBubba 
Member
Posts: 38

Age: 71
Loc: Illinois
Reg: 07-30-06
06-05-22 06:36 PM - Post#2842409    
    In response to japete92

  • Quote:
I do not know what you mean by '...all in one system, a front back system...'.



When I said this,,,I was referring to the fact that a single MC is an all in one system,,,,,meaning all 4 brakes use one port MC,, and one line. A dual MC is a front/back system, with 2 ports and separate brake lines.The car has functioned fine for 65 years, with a single MC and one brake line feeding all four drums. I had replaced the all the brake lines going to rear of car a few years ago. I am just trying to add a little safety factor,,, in case there is a brake line or hose failure, the dual mc setup would offer that. Thanks for all the help and conversations,,,

Bubba and Kathy
Illinois


 


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