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Post Info TOPIC: Dual master cylinder conversion, NO disc brakes


A Poncho Legend!

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Dual master cylinder conversion, NO disc brakes


Has anyone done a 1967 dual master cylinder conversion a 66 or older drum brake GM? I'm not interested in talking about disc brakes, that's for a different thread. 

if you've done this, did you change the line that goes to the back wheels from 3/16" to 1/4"? I'm wondering if that needs to be done to properly balance the hydraulics? 



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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)



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I have always changed up to the 1/4 inch line.  Mainly because thats the way it was done on the combination valve in 1967(on chevelles).  Also i think the combination valve would only accept a 1/4 inch line unless you could change the threaded fitting?     Is it really nessecary to use 1/4 inch line tho?   good question.



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Beaumontguru

MY BEAUMONT HAS 4 STUDDED TIRES AND 2 BLOCKHEATERS......AND LOTS OF OIL UNDERNEATH.  The other one has a longer roof.



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Well, I took it for a quick test down the block and back. The rear wheels are braking more than the front (could be adjustment but I think I'll change the line to the back to 1/4"). I'm betting that's the issue.

Really, when I think of it, I didn't need to add the 67 block because it doesn't do any metering I'm thinking. I could have just run the back line from the rear master port to the rear hose, and a line from the front master port down to the stock block on the frame with a plug on the rear port on it.

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)



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I had never seen this before but someone makes a nice kit if you don't want anything bulky for the conversion. Simple, front line in, 1 lines out to each front wheel, rear line in, 1 line out to rear.

t1.jpg



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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)



Canadian Poncho Superstar!

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The line size will be fine at 3/16" Carl. You'd only ever need the volume of 1/4" if you had multi piston disc calipers.

As long as you have working holdback valving, then 3/16" is plenty of line for two double acting pistons. The touchiness is another issue.

Add a dial type pressure control valve into the rear.



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65 Laurentian post, 67 Grande Parisienne 4 door HT. 
 


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cdnpont wrote:

The line size will be fine at 3/16" Carl. You'd only ever need the volume of 1/4" if you had multi piston disc calipers.

As long as you have working holdback valving, then 3/16" is plenty of line for two double acting pistons. The touchiness is another issue.

Add a dial type pressure control valve into the rear.


 You don't think line size has anything to do with the rears braking too much?

They don't feel touchy really as much as when I give a fairly firm stop (granted, the street has snow on it) the rears skid and the fronts don't.

It needs to look stock if possible so I'd prefer to do without a control valve. 

It sounds like Beaumontguru has made this same setup work when he's converted his cars so I think I'm going to try the 1/4" line to the back.



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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)



Poncho Master!

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Carl I put the dual master in my 65. I didn't change the rear line. Just made up an adapter from the 1/4 coming out of the combo valve to 3/16 line. Works just fine.

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65 Impala SS 2dr HT
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59 Impala 2dr HT
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Hmm. That is what I did on this one. I just bought a brass adapter so I could thread the 3/16" line from the back into the block that was made for 1/4". Maybe I'll try adjusting the shoes. 

This isn't on my car. It's on a 65 Beaumont that had a disc brake conversion that did NOT work nice at all and I converted it back to stock drums. Removed the booster/master/valve assembly from the disc brakes and put on an entire booster/master/block from a 67 power drum setup.

I haven't been able to take it out on dry highway to try it because the main streets are so messy/salted but on our snow covered side street the backs lock up on a firm stop and the fronts don't.



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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)



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Interesting block that inlineTube sells,  i never knew such a thing existed.  It would be a wickedly slick setup for an X-frame car!!  you may want to try that out on your own 66 some day.  The 67 block is nice only in the fact you get a brake warning light.

I would try adjusting the shoes on the beaumont,  im thinking that is the problem. 

But since it is the 65 beauont,  i would convert it to the 1/4 inch line too. and get a new rear brake hose(for a 67) at the same time(but thats just me)



-- Edited by beaumontguru on Saturday 16th of December 2023 09:12:32 AM

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Beaumontguru

MY BEAUMONT HAS 4 STUDDED TIRES AND 2 BLOCKHEATERS......AND LOTS OF OIL UNDERNEATH.  The other one has a longer roof.



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beaumontguru wrote:

Interesting block that inlineTube sells,  I never knew such a thing existed.  It would be a wickedly slick setup for an X-frame car!!  you may want to try that out on your own 66 some day.  The 67 block is nice only in the fact you get a brake warning light.

I would try adjusting the shoes on the Beaumont,  I'm thinking that is the problem.

 I was lying awake thinking about this last night.  I had trouble getting the front lines bled to my satisfaction because of very little clearance between the bleeder screw and the spindle. I couldn't get a hose onto the screw real well to use my vacuum bleeder properly. I might get a friend over to help me bleed the fronts again, using the brake pedal to pump them up. I betting air in the lines could certainly could make the system act like it is. And yes, I'm going to adjust the shoes as well. 

But since it is the 65 Beaumont,  I would convert it to the 1/4 inch line too. and get a new rear brake hose(for a 67) at the same time(but that's just me)

Funny you mention the hose! I actually changed the hose to the 67 rear hose and put a reducer in to connect to the 3/16" line. Reason for that was no local availability for the 65 hose, and I was thinking I might change the rear line to 1/4" anyway, so that made the most sense to do it.




 



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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)



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DANO65 wrote:

Carl I put the dual master in my 65. I didn't change the rear line. Just made up an adapter from the 1/4 coming out of the combo valve to 3/16 line. Works just fine.


 So your 65 is 3/16" to the back? Interesting, for 66 they put 1/4" to the back. That explains why the tube block down at the frame is not the same part number from 65 to 66. 



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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)

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