[Dragsix]

So I have driven my 57 for 46 years. If you can believe it, I took my driver’s test in the car when I was 16. I can’t believe it, lol, but it’s true. And all these years, I have driven on the single pot master. It failed on me just one time in 1978. Was the original master. Blew threw a stop sign and still did not understand what had just happened until I blew threw another one, lol. Limped it to the repair shop and the mechanic replaced it and showed me how to stick my head under the dash, peel the boot back and look for wetness. I replaced that master in the late 80s not for any reason other then it was old. In 2015 I had Whitepost restoration rebuild an original master and installed that when I got the car back on the highway after sitting for a number of years. So I am on my fourth single pot master in 46 years, no failures except for the first one.

My boys have both been on me to change over to a dual pot master for a while now. But the truth is I like the pedal feel I have and have always had with a single pot, the car stops fine, and other then that one episode when I was a teen, I have had no issues with the single pot. But the boys won’t let it be. And so I am waiving the white flag and will make the change over and see how I like it.

So tonight I had a little time to myself and decided to get this project off the ground. First thing, I needed a jig to mount the master on so I could add a few things to the system. What things? Well, a line loc for one. Why? Because I was a really broke teenager and I could not afford one when I was younger, lol. I don’t know that I will use it all that often, maybe at the nationals, maybe never, but I just don’t seem to be able to let that one go, lol.

The other things I want to add are inline residual valves. My car is a manual system with drum brakes. The original master had an internal pressure residual valve to keep some residual pressure against the wheel cylinder cups and the springs.

The dual masters, when new in the day, all had these rubber duck bill residual pressure valves. Two for a full drum brake system, one for a disc drum set up. The new masters that are sold today, and the rebuilt masters that are sold today do not have any pressure residual valves. They use to have them but not any longer. So I want to install a pair of Wilwood 10 pound inline residual valves to deal with that function.

260-1876 - Wilwood 10 lb Residual Pressure Valve - Moser Engineering

260-1876 - Wilwood 10 lb Residual Pressure Valve Master Cylinder Dimensions Wilwood Residual Pressure Valve Drawing Additional Dimensions...

www.moserengineering.com

That being said, the rebuild kits still come with them, at least they did two years ago. Here is what they look like. If you have an older master that has a removable brass seat in the output ports, you can use a sheet metal screw and remove the seat, rebuild the master, install the valves, and new brass seats (which come with the kit) and then you don’t need external pressure residual valves.

 

[Dragsix]

To start this little project, I grabbed an extra stock master and a 5 inch board, drilled a 1 1/2 hole for the back of the master, put the master on the board and then used the stock master as my guide for marking the position of the four holes, drilled the four mounting holes, and installed some bolts.

 

[Dragsix]

One of the issues I have is that I have two Holley 2300 carbs hanging off the intake on my 6 motor which makes clearance for a dual pot master at the back carb pretty tight. And I am not completely convinced this will all fit, it’s pretty close.

The masters sold for the early camaro are pretty fat compared to a stock master. This is one I just installed on my son’s 57. Note the width.

This master is a rebuilt original 67 GTO drum brake master. Member Hotrodhandyman (Bruce) is nearly, if not completely, all knowing, lol, and somehow knew the GTO master was thinner so that is what I am using. The length may also end up an issue but my measurements seem to indicate it will be close, but doable.

 

[Dragsix]

Picked up a bracket on eBay that is really for a proportioning valve. I don’t need a proportioning valve as I am all four drum brakes. I was going to use a 67 camaro distribution valve but after a lively discussion in another thread, it was determined that the distribution valves when triggered by a wheel cylinder failure don’t block off flow to the front or rear circuit when that occurs. All that it does is trigger a switch for the dash light on a camaro for brake issue. So I decided not to use one since there is no safety feature associated with it.

The bracket is just ok. A little crude but I have to modify it anyhow to do what I want to do, and for 20 bucks, it’s a bit of a time saver for me as a place to start. It also acts as a stiffener/brace for the inside pedal assembly. That assembly uses the four stock bolts as part of the attachment to the firewall. So the brace will bridge the two upper studs and act as the upper portion of the stock master, if that makes any sense, lol.

 

[Dragsix]

Bracket and master

Mocked up the Hurst line loc, got it leveled, marked the holes and drilled. You can see the lower part of the bracket is not itself level so I will have to do a bit of welding to make it look nice, as well as weld up the two larger holes (for a proportioning valve).

 

[Dragsix]

Made up the first line. Nicopp 3/16 tube covered by stainless spring wrap to make it look nice

The spring wrap I purchased on eBay but it was sold by Inline Tube.

3/16

3/16" Spring Wrap 8ft Length Stainless

www.inlinetube.com

 

[55wagoncrazy]

You must be expecting faster trip times at the Nationals this year.........= needing more brakes

Mikey

 

[Dragsix]

Next on the list is to weld up to two holes, make up a tab and weld it to the arm to mount a pair of insulated line clamps to stabilize the lines after the residual valves but that will have to wait, my timer just rang and I am out of time, lol.

 

[55Madman]

I was going to use a 67 camaro distribution valve but after a lively discussion in another thread, it was determined that the distribution valves when triggered by a wheel cylinder failure don’t block off flow to the front or rear circuit when that occurs. All that it does is trigger a switch for the dash light on a camaro for brake issue.

Mike - your comment raises a question for me and I'm curious how the 'lively conversation' caused you to not use the valve. My understanding is the dual master was developed and mandated to divorce the front and rear brake systems so that if one failed the other half would still be operable. Even with the valve, if a front wheel cylinder fails, the other front cylinder can indeed receive flow but obviously no pressure is available to actuate it. The other system (rear in this example), however, is still operable as before. The pedal will go down an extra amount as a result of the front no longer able to produce pressure, the spool valve slides off center to ground the warning light and close off the front system, but there should be enough pedal travel to actuate the rear brakes to the extent they are able to help stop the car - hence the safety value. I can't speak to the early Camaro distribution valve, per se; but the valves mandated for OE use when I went through ASE testing in '80 all look essentially like the GM one commonly used in today's aftermarket, and like you used on Patrick's car. That one, and all disc/drum applications, also include a metering valve (which that Camaro one would not have). So I'm guessing the lively discussion was disagreement on what the spool valve actually does...?
JR

 

[jhchevyparts]

Hi Mike: Since everything is apart, you might want to consider going a little further and powder coating the master cylinder. Impervious to the ugly results of any brake fluid spills.

 

[55 Tony]

If the older style valve doesn't isolate the front from the rear, how does it sense a pressure differential and trigger the switch? Sorry if this was covered in the other thread, I didn't read it all.

 

[Dragsix]

All good questions! What we discussed and discovered was that the combination valve used on the disc drum set ups is a distribution valve and proportioning valve “combination”. On those valves, if there is a failure of the say a rear wheel cylinder, there is a brass shuttle that will move with the loss of pressure and both trigger the switch for the dash light but also block off the leaking side of the system. So the front works but the rear is cut off from any flow that would push out with the pedal stroke.

The drum drum distribution valve has a sort of shuttle but if it moves because of a failure of say a front wheel cylinder, the shuttle only triggers a switch but does not block off flow to the front cylinders. So in this instance, you still have a functioning rear brake system, the reason for the dual pot master, but the front will leak with every pedal stroke. In other words the drum drum distribution valve is only in place to trigger the dash indicator light but does not cut flow to the offending wheel cylinder.

With a drum drum system, I need all four drums working as engineered, no slight delay in the rear brakes so a combination valve that has the delay metering function (the proportioning part of the combination valve) for the disc setup would make the drum drum brake System less effective if used on that type system. So while gaining the blocking function of the combination valves shuttle that will block off a front or rear brake circuit if you have a failure, you make the system less effective for overall driving because of the slight delay in the proportioning valve for the disc brakes.

So my choice was less mess to clean up if I have a wheel drum failure but a slightly less effective brake ing system, or deal with a mess in the event of a failure and have a better brake system. I have not had a failure since 78 when I was 17 and did not know much about brakes, so I went with the better brakes.

I did kick around the idea of installing the camaro distribution valve and wiring in a warning light but the truth is that I have kept my 57 pretty basic for all these years. The less stuff the less stuff to go wrong or fail so I decided to leave it out. So if I have a failure in a front or rear wheels cylinder, I will have enough in the opposing system to get the car stopped.

 

[55 Tony]

I kicked around the Idea of installing the distribution valve and wiring in a warning light but the truth is that I have kept my 57 pretty basic for all these years. The less stuff the less stuff to go wrong or fail so I decided to leave it out. So if I have a failure in a front or rear wheels cylinder, I will have enough in the opposing system to get the car stopped.

I hear you. And I have never had a brake malfunction that I didn't feel in the pedal immediately, so the warning light isn't very important in my eyes.

 

[twin engines]

Dual masters separate the hydraulic circuits for the reason single pots were dangerous.

My 81 camaro recently blew the rear drum slave cylinder seals (old and dry rotted) and all of the fluid in that chamber drained, but the fronts remained operational and fluid was at level. The brake light did come on as well...

Are the older dual masters different?

 

[twin engines]

All good questions! What we discussed and discovered was that the combination valve used on the disc drum set ups is a distribution valve and proportioning valve “combination”. On those valves, if there is a failure of the say a rear wheel cylinder, there is a brass shuttle that will move with the loss of pressure and both trigger the switch for the dash light but also block off the leaking side of the system. So the front works but the rear is cut off from any flow that would push out with the pedal stroke.

The drum drum distribution valve has a sort of shuttle but if it moves because of a failure of say a front wheel cylinder, the shuttle only triggers a switch but does not block off flow to the front cylinders. So in this instance, you still have a functioning rear brake system, the reason for the dual pot master, but the front will leak with every pedal stroke. In other words the drum drum distribution valve is only in place to trigger the dash indicator light but does not cut flow to the offending wheel cylinder.

With a drum drum system, I need all four drums working as engineered, no slight delay in the rear brakes so a combination valve that has the delay metering function (the proportioning part of the combination valve) for the disc setup would make the drum drum brake System less effective if used on that type system.

I kicked around the Idea of installing the distribution valve and wiring in a warning light but the truth is that I have kept my 57 pretty basic for all these years. The less stuff the less stuff to go wrong or fail so I decided to leave it out. So if I have a failure in a front or rear wheels cylinder, I will have enough in the opposing system to get the car stopped.

This makes sense...thanks!

 

[55Madman]

Appreciate the response - if I didn't have so much respect for the relationship you have with your car I'd try to talk you in to convert to front discs... I doubt I'd be the first to try. But I get your reasoning...

The less stuff the less stuff to go wrong or fail so I decided to leave it out.

 

[Dragsix]

That may happen. My tires age out this year and I am not one to mess with the tires. The 14 inch cragers that are on the car are pretty old, probably 1988 or so. I am going to try and replace them with new direct drill 15 inch ss cragers. My son and I installed disc brakes on his 57 although we are quite a bit away from having that car drivable. But if the pedal feel is decent, and the braking improved, I might consider it. Chevelle based disc set up apparantly will fit a 15 inch direct drill crager where as the 14 inch cragers I was made to understand that no disc set up will fit.

Right now I have Muscle Car Brake shoes on all four corners and the car stops pretty well, really well actually. Those shoes are a ceramic matrix material, relatively high tech for a low tech car but way way better then the organic shoes I had on the car at the 2015 nationals. Car would hardly stop. Clearly not enough friction coefficient on the organic material for an all four wheel drum brake car.

http://www.musclecarbrakes.com/index.html

I have driven at least two other 57s recently with disc brakes where the pedal went almost to the floor before the brakes started working, and frankly the stopping power was no better then what I have now and maybe even less. One had the metric calipers, the other chevelle calipers. I dont know if it was the install, bleeding, the quality of the kits or parts installed, but it was a little scary driving those cars, and I only drove them for just a bit and did not like the stopping at all.

 

[ETriggs]

The less stuff the less stuff to go wrong or fail so I decided to leave it out.

There is a saying amongst the older engineers that ring true for me. "A good engineer works until there is nothing more to add to the design. A great engineer works until there is nothing left to take away from the design." The older I get, the more I search for the great engineer in me and others.

 

[twin engines]

That may happen. My tires age out this year and I am not one to mess with the tires. The 14 inch cragers that are on the car are pretty old, probably 1988 or so. I am going to try and replace them with new direct drill 15 inch ss cragers. My son and I installed disc brakes on his 57 although we are quite a bit away from having that car drivable. But if the pedal feel is decent, and the braking improved, I might consider it. Chevelle based disc set up apparantly will fit a 15 inch direct drill crager where as the 14 inch cragers I was made to understand that no disc set up will fit.

Right now I have Muscle Car Brake shoes on all four corners and the car stops pretty well, really well actually. Those shoes are a ceramic matrix material, relatively high tech for a low tech car but way way better then the organic shoes I had on the car at the 2015 nationals. Car would hardly stop. Clearly not enough friction coefficient on the organic material for an all four wheel drum brake car.

I have driven at least two other 57s recently with disc brakes where the pedal went almost to the floor before the brakes started working, and frankly the stopping power was no better then what I have now and maybe even less. One had the metric calipers, the other chevelle calipers. I dont know if it was the install, bleeding, the quality of the kits or parts installed, but it was a little scary driving those cars, and I only drove them for just a bit and did not like the stopping at all.

I have the Chevelle kit on my Nomad...huge difference...manual setup, no vacuum

 

[Dragsix]

Could be, but i have been driving this bucket of bolts for nearly five decades with drum brakes. For now, just the move to a dual pot master is enough change for me at the moment, lol.