[SuperDad162]

I need some advice. I have a 64 GTO with drum brakes all around. I have power brakes on this GTO. I would like to convert the single master cylinder on it to the dual type for safety reasons. Any recommendations on what master cylinder to use? How would one off a 67 or 68 Firebird work? My brother used this type on an old Chevy he has.I have no plans to convert right now to disks. Also do I need to use a proportioning valve with this conversion? Any other info would be appreciated.

Bill Bcochran162@aol.com

[SuperDad162]

I need some advice. I have a 64 GTO with drum brakes all around. I have power brakes on this GTO. I would like to convert the single master cylinder on it to the dual type for safety reasons. Any recommendations on what master cylinder to use? How would one off a 67 or 68 Firebird work? My brother used this type on an old Chevy he has.I have no plans to convert right now to disks. Also do I need to use a proportioning valve with this conversion? Any other info would be appreciated.

Bill Bcochran162@aol.com

[Jim Doran]

Welcome to the Board. Good Question. I'm sure others will chime in, but I would email/phone one of the big disc conversion providers and ask them. You will probably end up buying the master cylinder from them or Performance Years.

http://www.ssbrakes.com

http://www.mpbrakes.com

[Ken K]

Since 1967 was the first year of the dual master cylinder that's what I would use in a 1964. Use the one from the A body cars. It would also be a good idea to get the prop valve. The master cylinder should be avalable from a parts store.

[428GTO70]

Actually, If you are not converting to disk brakes up front you dont need a proportioning valve, but just a junction block from a dual reservoir drum system to accomodate the extra line. Disc brake cars use proportioning valves because the disc front brakes need more pressure than the rear drums, and it delivers a different pressure to the rear lines than the fronts, while 4 wheel drums are equal pressure front and back. Hope this helps

[Ken K]

I don't know if you could call the 67 set up prop valve or a distribution block. The early single master cylinders use a brass block, The 67 set up is made out of cast iron and is set up a little different. I have both types to look at.

[SuperDad162]

Thanks everyone for the info.

I think I'll try to get one off of a 67 GTO or LeMans.

Is the GTO considered an A Body type?
Does this also include the Skylark, Cutlass, and Chevelle? What are Camaros and Firebirds considered as?

Thanks again,
Bill

[428GTO70]

Yes GTO is an A-body car, GTO, tempest, lemans, skylark, chevelle, cutlass, more...Good Luck.

[engineer]

IF YOU HAVE A BOOSTER ALREADY, THEN JUST SWAP ONTO IT WITH THE DUAL MASTER CYLINDER. THE IMPORTANT THINGS ARE THE MASTER CYLINDERS ARE MADE BY TWO COMPANIES AND MOUNT ONTO THE APPROPRIATE BOOSTER. BOOSTER ARE ALL THE SAME WHETHER DRUMS OR DISCS. A BOOSTER IS GOOD FOR LESS BRAKING EFFORT SO YOU DON'T NEED GREAT LEG MUSCLES ON THOSE WET ROADS. THE CYLINDERS WILL INTERCHANGE? BETWEEN THE BOOSTERS BUT LOOK AT THE REAR OF THE CYLINDER WHERE THE BOOSTER PUSHROD FROM THE PEDAL CONTACTS THE CYLINDER AND THERE ARE TWO TYPES. GET THE CYLINDER THAT HAS THE SAME PUSHROD CONTACT PAD AS THE ONE THAT CAME ON THE BOOSTER. THE CONTACT PAD IS EITHER FLUSH WITH JUST A DIMPLE OR THE PAD HAS A HOLE ABOUT PENCIL SIZE AND ABOUT AN INCH DEEP. WHEN YOU BUY THE NEW DUAL CYLINDER, IT WILL BE A MATTER TO LOOK AT GM CARS AFTER 1967 WITH ALL DRUM BRAKES FOR THE RIGHT MASTER. MY PARTS GUY CAN USUALLY LOOK AT 1967-1972 MODELS IN A COUPLE OF BOXES TO FIND THE RIGHT ONE.

YOU MAY ADD A COMBINATION BLOCK\ VALVE FOR AN ALL DRUM BRAKE SYSTEM IF YOU LIKE BUT ALL THAT WILL DO IS GIVE YOU A MOUNTING BLOCK FOR THE BRAKE LINES AND AN IDIOT LIGHT IF YOU CONNECT IT TO TELL YOU IF THE ONE OF THE DUAL CYLINDERS HAS FAILED. FOR MY 64, I LEFT IT OUT AS IT WAS JUST ANOTHER PLACE TO LEAK. AN ALL DRUM BRAKE SETUP DOESN’T NEED A PROPORTIONING VALVE BECAUSE THE PRESSURES TO EACH WHEEL CYLINDER ARE THE SAME, (WHILE THE DISC BRAKE SETUP REQUIRES DIFFERENT FRONT TO REAR PRESSURES). HOWEVER, YOU WILL NOW HAVE TO HAVE THE FRONT BRAKES SEPARATED FROM THE REAR LINE. SO THE TWO FRONT WHEEL BRAKE LINES ARE TEED TOGETHER WITH ONE MAIN LINE UP TO THE NEW DUAL MASTER CYLINDER AND THE REAR BRAKE LINE IS NOW SEPARATED FROM THE FRONT AND CAN GO DIRECTLY TO THE OTHER RESERVOIR ON THE DUAL MASTER. YOU WILL FIND THAT GM IN THEIR INFINITE WISDOM HAS ALL DIFFERENT SIZE TUBING LINES AND TUBING NUTS TO CONNECT THE DUAL MASTER CYLINDERS ON CARS WITH EXISTING SYSTEMS. THIS WAY SOME IDIOT DOES NOT GET THE WRONG LINES ON THE WRONG PLACES. FOR US, IT WILL BE A PAIN TO ADAPT, BUT IT CAN BE DONE. THE EASIEST WAY IS TO HAVE AN EXISTING CAR (LIKE FROM A JUNKYARD) WITH ALL THE RIGHT LINES\NUTS AND A MASTER. HOWEVER, I DON’T LIKE TO CUT EXISTING BRAKE LINES ON A CAR, SO I TRIED TO USE TUBE FITTING CONNECTORS (FOUND AT A WELL SUPPLIED AUTO STORE) AND NEW READY MADE BRAKE TUBING LINES OF THE RIGHT LENGTHS TO USE AS JUMPERS BETWEEN THE NEW DUAL MASTER AND THE OLD EXISTING 62 METAL TUBING LINES. THERE ARE SOME ADAPTERS FOR BRAKE CYLINDERS THAT GO FROM ONE SIZE TUBING LINE WITH DIFFERENT NUT SIZES. YOU WILL HAVE TO GO TO THE AUTO PARTS STORE WITH CYLINDER AND EXISTING LINE SIZES\NUTS TO FIGURE OUT THE EASIEST WAY TO CONNECT IT ALL TOGETHER. THAT IS THE BEST WAY TO GO WITH THE LEAST AMOUNT OF NEW TUBING, ADAPTERS AND CONNECTORS. REMEMBER THE MORE FITTINGS, THE MORE PROBABILITY OF LEAKING. ALSO, USE FLARE NUT WRENCHES ON THE TUBING NUTS SO YOU DON’T ROUND THEM OFF. ALSO ON THE EXISTING LINES, A LITTLE RUST BUSTER OIL AHEAD OF TIME MAY HELP IN GETTING THE 30+ BRAKE LINES APART.

[eskimonj]

Going along these same lines....

My 64 has already been converted to a 70 disc brake set up, but with no power.

My question, can I use a 64 booster with the 70 dual master, or do I need to go with a later booster as well?

I'd prefer to use the smaller 64 booster, reading other posts regarding the larger later boosters and inner fenders being dented to accomodate.

[Tom Vaught]

Because you are planning on using your Power brake
booster with your new master cylinder your swap
will be easier and safer. The power master cylinders have the shallow recess in the back of
the master cylinder. The non power brake set up
REQUIRES the deep recess in the back of the master
cylinder or on brake release action the release spring can pull the rod away from the recess and
the next time you will have NO BRAKES. I have a
67 power brake master if you cannot find one easily. Tom V.

[SuperDad162]

Hi Everyone,

I just have a comment to add. For my 64 GTO with power brakes, when I converted it to a dual master cylinder, the one for a 67 GTO with pwr brakes was different than mine( as far as the shaft length going into the master cylinder)Because the hole in the back of the 67 GTO master cylinder was shallow, I couldn't use it. I tried one from a 67 Firebird with PWR brakes and it matched up with my old single master cylinder. The hole in the rear for the shaft was deep, just like mine.

I've only owned this car since June and am restoring it for next summer. When I got it is was all apart. I am assuming the power booster came off of it originally ---- but who knows for sure. It does look like those in the shop manuals I have!
Thanks,
Bill

[eskimonj]

Anybody know where I can find pictures of the MC w and w/o the recess? I am not sure what I am looking for and some pictures may help.

Thanks

[Jim Doran]

It appears that the power booster for disc and for drum were two completely different sizes for '67. The power booster is 9" for a power drum car, and 11" for a power disc car. The 11" booster will only fit if you dimple the inner fender of a 64/65 GTO, or if you obtain a power disc inner fender from a 67.

Can someone explain what the functional differences between the two size boosters are ? I'd like to run an original 9" 65 power drum booster, but with a disc brake MC and combo valve. This way I don't have to dimple or change inner fender. Can anyone think of a reason why the power booster for a drum system won't work on a disc system ?

[eskimonj]

I was just looking at the website for Master Power Brake and you should be able to do that.

Look at the Q&A

http://www.mpbrakes.com/

[khkiley1]

Ok, I will start by saying that I am not that familiar with engineering of the brakes on A bodies.

But regardless of the setup, disk-disk, disk-drum, drum-drum, you do need a type of proportioning front-rear. You cannot have the same braking effort going to the rear brakes as the front or they will lockup as the weight transfers to the front of the car when you really lean on the brakes.

So unless there is another method, ie. reduced drum size, or swept fluid in the master cylinder, you will have problems if you don't have a proportioning valve.

You need to reduce the braking effort to the rear wheels or get ready to watch the rear end pass you the first time you panic stop.

The IQ and life expectancy of the average American just passed each other going in opposite directions.

[engineer]

http://ourworld.compuserve.com/homep...Drums_to_Discs

good site for pictures on this discussion. Yes you can use the 64 booster for power discs.