[mkoser]

Originally Posted by 6T5 Cat

Just wondering where you found, or was told this information? All of my GM Pontiac shop manuals and assembly manuals show and state that the front brake line goes to the front port and the rear brake line goes to the rear port of the master cylinder. Bob

No, that is incorrect. By design, the piston, or brake line connection, that is closest to the driver HAS to connect to the front wheel cylinders. This is to ensure that braking first occurs on the front wheels, then pressure built in the master cylinder forces the piston farthest from the driver to apply fluid pressure to the rear wheel cylinders.

Every dual master cylinder that I have ever seen is designed this way. Some newer cars split them left and right, but this is not the case in our old Pontiacs.

Thanks,

MK

[mkoser]

Originally Posted by mkoser

No, that is incorrect. By design, the piston, or brake line connection, that is closest to the driver HAS to connect to the front wheel cylinders. This is to ensure that braking first occurs on the front wheels, then pressure built in the master cylinder forces the piston farthest from the driver to apply fluid pressure to the rear wheel cylinders.

Every dual master cylinder that I have ever seen is designed this way. Some newer cars split them left and right, but this is not the case in our old Pontiacs.

Thanks,

MK

I should clarify, I was a bit tired when I wrote this last night. Anyway you hook up this master in a drum/drum configuration will work the same, since equal pressure is going to the front and the back. With that said, when they were designed, it was designed to provide full pressure, and longest stroke to the front brakes by way of a MECHANICAL connection from foot to hydraulic piston.

On disc/drum cars with a proportioning valve, the rear port must be connected to the front brakes, and the front port to the rear brakes.

Also, the biggest reservoir always is for the front brakes.

MK

[1967Tempest]

I was going to say that the Tempest has been wrong for years if that was true!!! LOL!!!!

I will say that the Tempest has had discs in front for the better part of 3 years. driving a drum/drum car takes some getting used to. The pedal travel on drum is shorter to lock the brakes up!!!

I am going to swap out to disc soon. BUT the above post for dual is dead nuts right on!!!!!!

Dave

[6T5 Cat]

Originally Posted by mkoser

No, that is incorrect. By design, the piston, or brake line connection, that is closest to the driver HAS to connect to the front wheel cylinders. This is to ensure that braking first occurs on the front wheels, then pressure built in the master cylinder forces the piston farthest from the driver to apply fluid pressure to the rear wheel cylinders.

Every dual master cylinder that I have ever seen is designed this way. Some newer cars split them left and right, but this is not the case in our old Pontiacs.

Thanks,

MK

Originally Posted by mkoser

I should clarify, I was a bit tired when I wrote this last night. Anyway you hook up this master in a drum/drum configuration will work the same, since equal pressure is going to the front and the back. With that said, when they were designed, it was designed to provide full pressure, and longest stroke to the front brakes by way of a MECHANICAL connection from foot to hydraulic piston.

On disc/drum cars with a proportioning valve, the rear port must be connected to the front brakes, and the front port to the rear brakes.

Also, the biggest reservoir always is for the front brakes.

MK

I find it interesting you claim as incorrect, and choose to ignore, information in the Pontiac Service Manual regarding dual master cylinder brake systems for 1967 and up classic Pontiacs. The information I stated is correct. The front port of the master cylinder feeds the front brakes and the rear port feeds the rear brakes and, accordingly, the master cylinder pistons are specifically calibrated, respectively. The engineers purposely used different size fittings for the front and rear ports of the M/C to prevent the brake lines from being installed to the wrong ports. It’s in the manual and it’s written by the GM engineers who designed the system, so you shouldn’t be dismissing it as incorrect. This info is correct for the A and F body cars, as well, and applies to manual, power, heavy duty power, and disc/drum brakes systems. I’ve been working on Pontiacs and Chevys since the early 60s and have never had a problem because of following the proper service manuals. You need to correct several things to have a safe and efficient brake system on your 64.

[1967Tempest]

So is there any ill effects from the rear port feeding the front brakes? I currently have it set-up that way..

[mkoser]

Originally Posted by 6T5 Cat

I find it interesting you claim as incorrect, and choose to ignore, information in the Pontiac Service Manual regarding dual master cylinder brake systems for 1967 and up classic Pontiacs. The information I stated is correct. The front port of the master cylinder feeds the front brakes and the rear port feeds the rear brakes and, accordingly, the master cylinder pistons are specifically calibrated, respectively. The engineers purposely used different size fittings for the front and rear ports of the M/C to prevent the brake lines from being installed to the wrong ports. It’s in the manual and it’s written by the GM engineers who designed the system, so you shouldn’t be dismissing it as incorrect. This info is correct for the A and F body cars, as well, and applies to manual, power, heavy duty power, and disc/drum brakes systems. I’ve been working on Pontiacs and Chevys since the early 60s and have never had a problem because of following the proper service manuals. You need to correct several things to have a safe and efficient brake system on your 64.

This may be (and probably is) true for drum/drum cars, but what about disc/drum cars?

A quick google search came up with this article http://www.auto-repair-help.com/auto...r_cylinder.php

I'm not going to disbute your shop manuals, or you, but any car with a dual master set up that i have seen has the rear port to the front brakes, and the front to the rear. In the event of a leak, you want the FRONT portion to build pressure faster than the rear. If the front portion was at the front of the master, and you had a leak there, the rears would set up hard, and now, possibly causing your car to skid. You want the rear brakes to be fed by the end of the pedal travel, in a front leak situation, to effect a slow and controlled stop.

As far as proportioning goes, on these drum/drum masters, (our big ponchos) the proportioning takes place at the wheel cylinders, not in the master cylinder. The front and rear wheel cylinders are of different diameter.

Just my .02, can't find any info either way to show I'm right or wrong. Use it as you see fit. I've got my 64 plumbed this way, it it stops on a dime.

MK

[60man]

Originally Posted by 6T5 Cat

I find it interesting you claim as incorrect, and choose to ignore, information in the Pontiac Service Manual regarding dual master cylinder brake systems for 1967 and up classic Pontiacs. The information I stated is correct. The front port of the master cylinder feeds the front brakes and the rear port feeds the rear brakes and, accordingly, the master cylinder pistons are specifically calibrated, respectively. The engineers purposely used different size fittings for the front and rear ports of the M/C to prevent the brake lines from being installed to the wrong ports. It’s in the manual and it’s written by the GM engineers who designed the system, so you shouldn’t be dismissing it as incorrect. This info is correct for the A and F body cars, as well, and applies to manual, power, heavy duty power, and disc/drum brakes systems. I’ve been working on Pontiacs and Chevys since the early 60s and have never had a problem because of following the proper service manuals. You need to correct several things to have a safe and efficient brake system on your 64.

Ditto.....Got to be careful when selecting master cylinders.. I bought one for a 70 something Gm/factory disc-drum ...it had a large/huge front resivor in the master cylinder..I would run out of fluid if I used the "small" rear fluid resivor for the much larger front disc calipers ?? JMO....Comments..
I'm getting ready to do a 4 wheel disc conversion now..all will change.

[61 vent]

Hello guys, just throwing a little parts info out there. In the May muscle car review under new products. Speedway motors has a corvette style master cylinder that is drilled on both sides, so that you can hook up your lines on either side. The cast iron version is 49.00 Item #:91031321 I may look into this when I do my swap. We will see.

[MOJO Catalina]

FYI: This may have been covered already, but when running the brake lines be sure not to create "traps" (like the ones under your kitchen sink only in the upwards direction) where air bubbles can collect. I did this at first coming out of the MC due to slim clearance. I had a hard time bleeding it all out so I shortened the original brake line and rolled the one coming out of the MC downward so all the air would return to the reservoir and bubble upward and out.

Sounds like the MC mentioned above will be the best situation for us moving forward.

[mkoser]

Originally Posted by 61 vent

Hello guys, just throwing a little parts info out there. In the May muscle car review under new products. Speedway motors has a corvette style master cylinder that is drilled on both sides, so that you can hook up your lines on either side. The cast iron version is 49.00 Item #:91031321 I may look into this when I do my swap. We will see.

Remember, this above mentioned master cylinder is for DISC/DRUM brakes. It won't work as a simple drum/drum dual master upgrade.

mk

[61 vent]

That is a very good point, thanks for pointing that out. I quote from the magazine article ( the 1 inch bore size will work with either manual or power brakes) I have sent an email off to Speedway motors, asking about this question, and I will post the answer as soon as they respond. While browsing there website I found that they have a few complete kits with booster and master cylinders. Thanks again for pointing that out, I would hate to lead anyone down the wrong path.

[mkoser]

Originally Posted by 61 vent

That is a very good point, thanks for pointing that out. I quote from the magazine article ( the 1 inch bore size will work with either manual or power brakes) I have sent an email off to Speedway motors, asking about this question, and I will post the answer as soon as they respond. While browsing there website I found that they have a few complete kits with booster and master cylinders. Thanks again for pointing that out, I would hate to lead anyone down the wrong path.

Right. You can either have:
1. Manual drum/drum brakes
2. Power drum/drum brakes
3. Manual Disc/Drum
4. Manual Disc/Disc (I believe some Corvettes had this set up, but I'm not sure.)
5. Power Disc/Drum

For our original, big cars, we want to go with either:
1. Power drum/drum
2. Manual drum/drum.

depending on if you have a power booster or not.

If you put a disc master cylinder on your drum/drum car, you're front brakes will stick. This is because the master cylinder holds pressure to the front brakes, to reduce pedal travel.

MK

[61 vent]

Here is my response, from Speedway motors



I'm not shure of the master cylinder part number you're refering to, however we do have a master cylinder that may fit your 62 pontiac. If your present master cylinder has a attaching distance of 3 1/4 inches, that is between the bolts that attach it to your booster, Our PN # 91031428 aluminum master cylinder with stainless steel sleeve would work.
It features a 1" bore that is compatible with the drum setup, has 3/8 x 24 inverted flare outlets. Some brake line adaptation may be required.


Good luck with your project and if you need any other help feel free to contact us for parts ordering or tech assistance.




Jack Hastreiter
Street Rod Tech
1-800-979-0122 ext. 2959

[punisher7]

I took my master cylinder off today and the dowel that goes from the booster into the master is to long, does anybody know if these dowels can be bought at the correct length or do I have to just cut it down? Looks to be close to 2" to long.

[Deadhead]

you have to cut to fit. When I did my '66, which took the same original master as '63 and was replaced with a '68 dual like you are using, my rod had several markings on it. Whether it was coincidence or not - one of them corresponded to the correct length. I started just longer than that and worked my way down. I rounded it off like original on a grinding wheel.

[T.Weber]

If you didn't want to cut up your factory rod Speedway has severeal rods that you can cut to fit for about $10.00

http://www.speedwaymotors.com/Univer...Long,9330.html

This tech article has been a great healp to me. I haven't converted my 62 Catalina to a dual master yet but I did convert my 64 Chevy pickup to power drum brakes with a dual master cylinder. I of course had to make some minor changes to get it all to work in a chevy truck. A specal booster bracket off the chevy truck site $55.00, a junk yard booster off a 92 Chevy truck $20.00 (studs are metric 10 mm 1.50 pitch) I cut off the round end of the rod from the booster and threaded it a couple of inches down using 3/8"-24 threads a master cylinder for 67 Cadillac $24.99 + $10.00 core, two 3/8"-24 coupling nuts, about $5.00 from Orchard Supply, one grade eight 3/8"-24 x 4" bolt from Orchard Supply that I cut the head off and threaded the head end with 3/8"-24 threads about $2.00 and one 3/8" male heim joint with 3/8" - 24 threeads, I used a 3/8" booster check valve and moulded hose off a 78 Dodge pick up and a vacuum fitting with several ports to work the vacuum modulator, A/C vacuum line and booster check valve plus a an extra port, this came from a Ford Ranger that had fuel injection (it was easy to get to) What can I say, I'm cheap, lazy and I love to junk yarding.

This site and the people on it are the best!

[mkoser]

Originally Posted by Deadhead

you have to cut to fit. When I did my '66, which took the same original master as '63 and was replaced with a '68 dual like you are using, my rod had several markings on it. Whether it was coincidence or not - one of them corresponded to the correct length. I started just longer than that and worked my way down. I rounded it off like original on a grinding wheel.

I wonder what the difference is. On my 64, it was total "plug and play." I didn't have to alter the push rod at all.

MK

[hellerods]

I am in the middle of swiching master cylinders from a single to a dual ( 1969 Bonnie drum/drum) on my 64' catalina ( single). I have run into a problem, the plunger and spring retainer from the 64' will not fit the new (69') MASTER CYLINDER! Anybody know where I can find the parts that go between the pedal and M/C ?? Thanks Lee

[MOJO Catalina]

Is the car manual or power brakes? Are you converting from single manual to dual manual or dual power brakes? Or is it single power brakes to dual power brakes?
The fork plungers are different lengths between power and manual and some master cylinders have different depths in the plunger cup. It's mentioned elsewhere in here so go back in this topic and see if you can find that part.

[hellerods]

Sorry I thought I was clear about my brake conversion attempt. My car is a factory stock drum/drum non-power, single M/C. I am trying to change to drum/drum , non-power, dual M/C. And I have read the total thread three times and still do not see the infomation that I need about a non-power brake car M/C conversion. I have a problem with the plunger/rod assy. between the two M/C's. My new M/C (from 1969 bonnie) Car Quest # BRK E66712 fits on the car's firewall and will bolt up no problem. The problem is the plunger from my original 64'M/C set up is uncompatable with the new MC. The new MC has a different rod retaining snap-ring set-up, the original plunger/rod assy is captured with a snap wire that allows the end of the plunger and the brass washer to be retained in the end of the MC. The new MC has a different style of plunger/ capture rod set-up, the new MC uses some other method of retaining the end of the rod assy. I need the parts from a 69' car that go between the MC and the brake pedal, or at least a picture? Thanks Lee