[mkoser]

Originally Posted by 1967Tempest

yeah, the brake stop FAST!!!! I think this might be because of the rearmost reservoir on the front brakes.

Again,

Mine is set up the same way as yours, and mine stops fine... just like it did when it was new.

MK

[mkoser]

Originally Posted by 6T5 Cat

They may be touchy because, with the lines being hooked up as they are, the higher pressure front mc piston is actuating the smaller rear wheel cylinders and causing a tendency to lockup. How old are your brake lines, they may be rusting inside, so check the brake fluid for rust setiment and tiny rust particles. Also check for the obvious grease or oil contminants on the shoes/pads and drums/rotors.

Are you sure you used a drum/drum master? If you used a disc/drum master (or sometype of proportioning valve) you'll get touchy, sticky brakes.

The pressure out of the master cylinder circuits HAS to be the SAME.

Think of how it was before the dual swap... it was ONE circuit, and ONE pressure. Any and all proportioning takes place directly in the wheel cylinders, not in the master, the lines, or any type of block or valve. This is a simple brake system. We need to keep it simple.

The only way one circuit has more pressure than the other is if the other circuit develops a leak. That's it.

I agree, and accept your evidence of which line goes where, but there HAD to be situations in cars (even in our cars) where they were installed reverse. As stated, there are many many many cars out there that have their lines "backwards" from the factory.

MK

[mkoser]

Originally Posted by mkoser

Again,

Mine is set up the same way as yours, and mine stops fine... just like it did when it was new.

MK

Leaky wheel cylinders, contaminated brake shoes, shoes out of adjustment, rusty drums, incorrect brake hardware, and faulty brake booster are all things that come to mind that may cause a touchy brake pedal.

[Deadhead]

What I have been saying from the beginning is that for this to be right you have got to get the valve from the donor car pictured in image 5A-6 provided by 6t5 Cat. labeled 'valve'. This is the metering block that the lines plug into. It is my understanding that this also proportions front and rear brakes. It is not merely a housing for the trouble light that goes to the dash/jct block. If you use your existing Jct. for the lines then if the lines are the same size, I am sure it makes no difference front or rear as pressure is pressure. From the internal diagram, there does not appear to be any proportional difference between the front and rear valve in the MC.

I think this may be the source of some of the confusion. Mine is hooked up as the factory book shows and I did it going from the way the donor car I took my parts was including the metering block. These blocks also have varying size lines from the block to front and rear brakes which I assume proportion the VOLUME of fluid going to each set of cylinders, which would make a difference if hooked up backwards. Especially under duress when the fluid is heating up.

[mkoser]

Originally Posted by Deadhead

What I have been saying from the beginning is that for this to be right you have got to get the valve from the donor car pictured in image 5A-6 provided by 6t5 Cat. labeled 'valve'. This is the metering block that the lines plug into. It is my understanding that this also proportions front and rear brakes. It is not merely a housing for the trouble light that goes to the dash/jct block. If you use your existing Jct. for the lines then if the lines are the same size, I am sure it makes no difference front or rear as pressure is pressure. From the internal diagram, there does not appear to be any proportional difference between the front and rear valve in the MC.

I think this may be the source of some of the confusion. Mine is hooked up as the factory book shows and I did it going from the way the donor car I took my parts was including the metering block. These blocks also have varying size lines from the block to front and rear brakes which I assume proportion the VOLUME of fluid going to each set of cylinders, which would make a difference if hooked up backwards. Especially under duress when the fluid is heating up.

1. My 1964 has no brake trouble light.
2. My 64 has no "valve." What it did have (and is still used in the front brake circuit) is a Junction block. Not a metering block, valve, proportioning valve, or anything else. It is simply a fitting that allow one "input" to be delivered to three (two front, and one rear) "outputs".
3. All of my original brake lines were the exact same size.
4. Again, the way it was originally set up was: One line from master cylinder into junction block, then one line to each front brake, and one line to the rear, which was split to each rear brake.

Now if you are working with a DISC/DRUM set up, then the above does not apply. I am having a hard time reading those scans, but to me that looks like info for a 1967 DISC/DRUM set up. No?

MK

[mkoser]

Ok, one last thing. Let's turn this "discussion" around.

If the way I engineered my brake system in my 1964 Catalina with Drum/Drum brakes is NOT correct (or even possible to some), then why does it work in my car?

MK

[Deadhead]

Your car did not originally come with a dual master nor did it come with the additional components that those systems had. How you have it set up does work, but it is not the way the first dual master cars' systems were engineered. What we are saying is that on the first cars that had dual masters from the factory that this is how they are set up.

Clearly this stuff was engineered with these components in this configuration for a reason. I personally am not interested in finding out the reason my second guess did not work when I am slamming the brakes on from 70 MPH when the proportion might actually make a difference in how the car behaves. That is why I chose to use all the components installed the way the factory literature has them. I am not saying your system does not work or is wrong. I am just saying it has not been tested to the fullest and that none of us here knows all the specifics of the engineering whys and wherefores, so why take a chance?

[1967Tempest]

That does bring up a good point. Have you had an "Oh S@#T" moment where you needed to slam on them?

If the rears lock up first that is gonna cause a lot of issues..

Just discussing here, civil, like a DISCUSSION should be..

Dave

[Deadhead]

I have rock-n-rolled in my car I converted, and it is a BMF wagon. I do use my TH400 to aid braking as well, but the braking system is balanced or proportioned correctly for hard stops and braking into turns with loads on the front end. Brake in - power out!

[6T5 Cat]

Originally Posted by mkoser

Are you sure you used a drum/drum master? If you used a disc/drum master (or sometype of proportioning valve) you'll get touchy, sticky brakes.

The pressure out of the master cylinder circuits HAS to be the SAME.

Think of how it was before the dual swap... it was ONE circuit, and ONE pressure. Any and all proportioning takes place directly in the wheel cylinders, not in the master, the lines, or any type of block or valve. This is a simple brake system. We need to keep it simple.

The only way one circuit has more pressure than the other is if the other circuit develops a leak. That's it.

I agree, and accept your evidence of which line goes where, but there HAD to be situations in cars (even in our cars) where they were installed reverse. As stated, there are many many many cars out there that have their lines "backwards" from the factory.

MK

What you state is incorrect. The two pistons in a dual master cylinder are calibrated to provide different pressures, via the correct amount of brake fluid, to the wheel cylinders. If you read the page I attached regarding master cylinder operation you will see that information (where I placed the arrow). Not listed is how the calibration is done. The calibration is accomplished by drilling small bleed holes around the front edge of the piston face. As the piston moves forward, fluid bleeds through the bleed-holes to a cavity on the back side of the piston face. The fewer the number of holes, the higher the pressure. Another important component of the balanced system is to ensure proper pressure to the front wheel cylinders is using the correct size brake lines. Your car, equipped with the single master cylinder, uses 1/4" front brake lines. Now, in order for your brake system to operate safely ,and properly, you need to install a 67-70 GM distribution block which will allow you to install the proper 3/16" front brake lines. Consider how your brakes are configured now. Your front brakes (larger wheel cylinder) is being powered by the lower pressure rear piston and is connected by ¼” brake lines that are 78% larger than the design spec calls for, which means even less pressure to the front wheel cylinders. On the other hand, the smaller rear wheel cylinders are now powered by the larger front piston and will be over powered and prone to brake lockup. If you have to make panic stop with your car as it is plumbed now, most likely your car will swap ends and maybe even experience a rollover during the spin.

The distribution block used on 67-70 GM cars, and earlier Cadillac vehicles, is the same for all GM makes and does not meter or proportion the front brakes, it simply separates the two systems. Disc brake cars (GM) 1967-70 had what Pontiac called a “Metering Valve”, and was also referred to as a “Hold-Off Valve”, that was mounted under the master cylinder that was used to delay front wheel braking action until rear wheel brake line pressure reaches about 75 psi. If you look at the attachment of the disc brake page I provided, you will see the two valves and that the front brakes are plumbed through the metering valve then to the distribution valve/block. All GM disc brake cars (67-70) used both the metering valve and the distribution block, but the drum brake cars used only the distribution block. In 1971 the distribution block and the metering valve were combined into one unit and was used on the disc brake cars. The drum brake cars continued to use a regular distribution block.

In the Pontiac Service Manual under the topic of master cylinder repair, it stresses several times that when repairs are made to the master cylinder it is of Critical importance to install the front and rear in the correct positions.

I hope you will consider the info I’ve posted. I’m not trying to bust your balls, Matt. I just want you and your family to have a safe cruise.

[6T5 Cat]

Originally Posted by Deadhead

What I have been saying from the beginning is that for this to be right you have got to get the valve from the donor car pictured in image 5A-6 provided by 6t5 Cat. labeled 'valve'. This is the metering block that the lines plug into. It is my understanding that this also proportions front and rear brakes. It is not merely a housing for the trouble light that goes to the dash/jct block. If you use your existing Jct. for the lines then if the lines are the same size, I am sure it makes no difference front or rear as pressure is pressure. From the internal diagram, there does not appear to be any proportional difference between the front and rear valve in the MC.

I think this may be the source of some of the confusion. Mine is hooked up as the factory book shows and I did it going from the way the donor car I took my parts was including the metering block. These blocks also have varying size lines from the block to front and rear brakes which I assume proportion the VOLUME of fluid going to each set of cylinders, which would make a difference if hooked up backwards. Especially under duress when the fluid is heating up.

Bruce, here's what I wrote to Matt about the distribution block/valve is a drum brake vs a disc brake system.

The distribution block used on 67-70 GM cars, and earlier Cadillac vehicles, is the same for all GM makes and does not meter or proportion the front brakes, it simply separates the two systems. Disc brake cars (GM) 1967-70 had what Pontiac called a “Metering Valve”, and was also referred to as a “Hold-Off Valve”, that was mounted under the master cylinder that was used to delay front wheel braking action until rear wheel brake line pressure reaches about 75 psi. If you look at the attachment of the disc brake page I provided, you will see the two valves and that the front brakes are plumbed through the metering valve then to the distribution valve/block. All GM disc brake cars (67-70) used both the metering valve and the distribution block, but the drum brake cars used only the distribution block. In 1971 the distribution block and the metering valve were combined into one unit and was used on the disc brake cars. The drum brake cars continued to use a regular distribution block.

[Deadhead]

I stand corrected. Clearly someone here knows exactly how the system was engineered. I should have known.

Thanks for the clarification. Nothing makes my day more than learning something.

[mkoser]

Originally Posted by 6T5 Cat

What you state is incorrect. The two pistons in a dual master cylinder are calibrated to provide different pressures, via the correct amount of brake fluid, to the wheel cylinders. If you read the page I attached regarding master cylinder operation you will see that information (where I placed the arrow). Not listed is how the calibration is done. The calibration is accomplished by drilling small bleed holes around the front edge of the piston face. As the piston moves forward, fluid bleeds through the bleed-holes to a cavity on the back side of the piston face. The fewer the number of holes, the higher the pressure. Another important component of the balanced system is to ensure proper pressure to the front wheel cylinders is using the correct size brake lines. Your car, equipped with the single master cylinder, uses 1/4" front brake lines. Now, in order for your brake system to operate safely ,and properly, you need to install a 67-70 GM distribution block which will allow you to install the proper 3/16" front brake lines. Consider how your brakes are configured now. Your front brakes (larger wheel cylinder) is being powered by the lower pressure rear piston and is connected by ¼” brake lines that are 78% larger than the design spec calls for, which means even less pressure to the front wheel cylinders. On the other hand, the smaller rear wheel cylinders are now powered by the larger front piston and will be over powered and prone to brake lockup. If you have to make panic stop with your car as it is plumbed now, most likely your car will swap ends and maybe even experience a rollover during the spin.

The distribution block used on 67-70 GM cars, and earlier Cadillac vehicles, is the same for all GM makes and does not meter or proportion the front brakes, it simply separates the two systems. Disc brake cars (GM) 1967-70 had what Pontiac called a “Metering Valve”, and was also referred to as a “Hold-Off Valve”, that was mounted under the master cylinder that was used to delay front wheel braking action until rear wheel brake line pressure reaches about 75 psi. If you look at the attachment of the disc brake page I provided, you will see the two valves and that the front brakes are plumbed through the metering valve then to the distribution valve/block. All GM disc brake cars (67-70) used both the metering valve and the distribution block, but the drum brake cars used only the distribution block. In 1971 the distribution block and the metering valve were combined into one unit and was used on the disc brake cars. The drum brake cars continued to use a regular distribution block.

In the Pontiac Service Manual under the topic of master cylinder repair, it stresses several times that when repairs are made to the master cylinder it is of Critical importance to install the front and rear in the correct positions.

I hope you will consider the info I’ve posted. I’m not trying to bust your balls, Matt. I just want you and your family to have a safe cruise.

Ok, I'll accept your argument, and I'll conclude with one last thing.

If the master is designed to produce different pressures and volumes, why would cars that were originally set up with drum/drum dual masters have different size wheel cylinders in the front and the back? It wouldn't make any sense to achieve any more proportioning in the wheel cylinders if your master already did that for you.

Page 5-2 of your scans in the paragraph with the arrow clearly states that hydraulic pressure in both circuits is the same.

I'm happy with the way my car brakes. It is a modification of the original. In testing, I've locked em up to make sure that everything held, and it would stop. It did. I feel safer having a dual circuit system, and will leave it the way it is.

Since it appears that this thread hasn't actually benefited anyone, since I've been providing bad information, I ask that it be totally removed.

[1967Tempest]

Originally Posted by mkoser

Since it appears that this thread hasn't actually benefited anyone, since I've been providing bad information, I ask that it be totally removed.

WHOA!!!!!!! Slow down Tonto!!!!

It is threads like these that MAKE the forums... A difference of opinions is what we need to see. Maybe over in the Exhaust forums they get out of control. But us Darksiders are more civil.. This thread should be sticky, not removed. Mkoser, you started a great thread and had both sides. You should feel good that the thread had so many hits and replys...

6T5 Cat said it best.... Safe Cruise!!!! That is what it is all about. This is one of the best threads. At least we are talking and not shouting right??

Dave!!!!

[BigAquaBonney]

Originally Posted by 1967Tempest

WHOA!!!!!!! Slow down Tonto!!!!

It is threads like these that MAKE the forums... A difference of opinions is what we need to see. Maybe over in the Exhaust forums they get out of control. But us Darksiders are more civil.. This thread should be sticky, not removed. Mkoser, you started a great thread and had both sides. You should feel good that the thread had so many hits and replys...

6T5 Cat said it best.... Safe Cruise!!!! That is what it is all about. This is one of the best threads. At least we are talking and not shouting right??

Dave!!!!

Agreed. I've learned a ton about brakes in this thread. At the end of the day, I hope there is a laundry list of suitable parts and special care (abbreviated) instructions for my 63 GP--which I hope to convert in the fall. I would hope that the thread is not deleted.

[6T5 Cat]

[QUOTE=mkoser;4351720]

"Page 5-2 of your scans in the paragraph with the arrow clearly states that hydraulic pressure in both circuits is the same."

Matt, read that scan again. What it is saying is the hydraulic forces acting on the two pistons are the same and therefore the pistons move in unisun. However, remember (first sentence) the pistons are calibrated differently to displace the correct amount of fluid to their respective wheel cylinders.

As far as having this thread removed, I think it should remain. It has created an exchange of thoughts and information. I'm sure some members have benefited from the discussions. Isn't that the purpose of these forums? Heck, I've been working on these old Pontiacs since they were new back in the 60s and I still pick up bits of information, or I'm reminded of things I've forgotten.

[Deadhead]

I don't think anyone is criticizing anything. If you are happy and things work to your satisfaction you should stick with it. I think that people here just care about the safety of the other members and want them to have all the information available to ensure they are as safe as possible. I DON'T THINK that any of the posts are meant to be in the Corvette crowd vein of: If you did not do it a particular way then your car is not technically correct and wrong. My cars are living examples of not thinking like this.

Enjoy your work you have done and have fun.

[mkoser]

I'm not arguing, but I admit, I reread some of my earlier posts and one I reversed the terms "front" and "rear" which may create some confusion.

I also think that both "arguments" are correct and incorrect. The problem I have defending my opinion is that 1) My 1964 Pontiac was never created with drum/drum power 2 circuit brakes. I can't cite any shop manual information on its operation. I have to rely on dirty science and the real life application.

I still think the scans we are looking at for the 1967 Tempest are for a DISC/DRUM master cylinder.

Look at this page from MP Brakes
"http://www.mpbrakes.com/technical-support/reference-master-cylinders.cfm"

Descriptions
Your master cylinder is the heart of your braking system. In order for your system to function properly you must utilize the correct cylinder for your system's demands. The following brief descriptions should help you in determining what master you will need.

DRUM / DRUM
A drum / drum master is designed to deliver fluid pressure and volume to the front and the rear of a braking system in equal proportions. Drum brakes will require less fluid and pressure than disc brakes. Typically a drum brake master will be smaller than a disc master and the fluid reservoir chambers will be equal in size. Since drum brakes require the use of residual pressure valves the original drum master cylinders had residual valves built into the outlets. Later model aftermarket units do not have these valves and they must be installed in the lines externally. Failure to incorporate residual valves will cause spongy brakes.

Generally speaking it's not a good idea to use a drum brake master for disc brakes since the amount of fluid the cylinder pushes will not be sufficient.

DISC / DRUM
A disc / drum master is designed to push more fluid volume to the front disc brakes since disc brakes require more volume than drum brakes. Generally speaking a disc / drum master will have one fluid reservoir larger than the other.This is because the disc brake pads wear faster than the drum shoes and the fluid reservoir will drop faster. Original disc / drum masters had a built in residual pressure valve to the rear drum brakes only.

Never reverse the outlets on a disc / drum master. Doing this will cause the front disc brakes to drag excessively from the residual pressure valve.

DISC / DISC
A four wheel disc brake master cylinder is designed to supply more fluid pressure and volume to the rear disc brakes than the disc / drum master does. This is acheived through an internal piston re design. The piston that feeds the rear brakes on a disc / drum master will run out of stroke, limiting the amount of fluid pressure and volume that may be supplied to the rear isc brakes.

The four wheel disc master redesign delivers the extra needed volume and pressure to the rear allowing your rear disc brakes to function properly. If you attempt to use a disc/drum master on a four wheel disc system you will get poor rear brake function and experience a spongy brake pedal with a long pedal travel."

They too indicate that drum/drum master cylinder circuit outputs are the same proportionally. They specifically state pressure AND volume is the same.

[joeg]

We have alot of redunduncy here, looks like this whole thing started back in 8/8/10 by cheesepocket followed up by a new thread by mkoser 8/11/10. Would have been nice if the information in both threads was condensed into one. The information in both threads is valuable.

[Scarebird]

We make a semi-custom bracket that mounts the "BK" code 1985-87 dual 9" booster on different cars. The test car is a 64 Catalina; we will get some pics and post them. The later booster allows 66 and later masters to be used.