1956 Brake Booster Replacement

I have my brake booster in okay condition, but I was looking to see about replacing it with something more modern. Has anyone had any success putting a modern brake booster in the same position as the stock one? I figure fabricating a bracket wouldn't be too much of a hassle, but more of finding a modern brake booster with a long enough stem. Just curious if anyone has attempted it, thanks in advance!

Just curious. What would replacing your existing OEM operational vacuum housing unit with that of a more modern looking vacuum diaphragm unit accomplish as both create adequate vacuum other than the obvious units in the end just looking different in shape, attachment and appearance ?

Ease of mind more so for my mother, who believes two lines coming from the MC are better than one. I've been on the fence about this one for a while and in the end I just want something more modern to power the brakes so replacing components is readily available and affordable, and not an arm and a leg through a remanufacturer/redistributor. The car has been sitting for 40 years at my grandpa's house, he bought it brand new in '56. I just had the 322 rebuilt last year and now I'm in a rush to get the car road worthy due to family issues (lost title, etc.), so this year's taxes have gone towards the Dynaflow rebuild and essentials like replacing the entire brake system. I've already measured that a 7 inch booster thats approx. 5 inches long would fit in the original spot of the MC was no longer than 8 inches before it makes contact with the steering box, I was just curious if anyone had ever made a similar modification.

On an unrelated note, since I can't quite test the vacuum from the engine yet and I can't find the specifications in the shop manual, can anyone give me the average idle vacuum for the 1956 322 Nailhead?

Then you must be referring to the Master Cylinder and not the vacuum chamber, as a dual split reserve master cylinder will have a split reservoir providing fluid for the front brake lines and the other for the rear brake lines.

Discussion: But each type system, i.e. split vs. mono have their own built-in individual weaknesses and strengths.

The weakness of this so called "modern" split setup is in the master cylinder itself since they are constructed utilizing rubber based plunger/bore wall seal type pistons which can and do often go bad not only due to the physical wear and tear from inner cylinder drag much like that of a piston ring in the engine, but additionally also from the deterioration of the rubber seal type plunger from the brake fluid itself and also from the hydroscopic properties of brake fluid which over time attracts and accumulates atmospheric moisture causing rust thoughout the metal based braking system.

Your original single reservoir power brake setup from the factory is constructed and designed much differently. First it does not rely on a pushing rubber sealed plunger/bore type delivery system but rather on the negative displacement of a metal plunger that does not have a cylinder bore to ride in thus having no wear and tear on the piston itself nor an inner cylinder bore to wear it down. It simply displaces the fluid by the amount the metal mass the plunger takes up in space within the reservoir fluid chamber itself. It has shaft seals placed along it's length to seal the shaft and are in turn protected from the brake fluid itself, unlike that of the exposed rubber sealed pushing plunger/bore type system. However, yes hese shaft seals can and do wear over time but there are a great number of them positioned along the shaft to minimize any possible overt leakage from a properly maintained system. Their only real weakness is where the steel lines end and the rubber lines begin and terminate at either the front wheels or at the center area of the rear end to allow for suspension movement and travel. With that said, the modern dual reservoir system shares this same weakness as it too necessitates this same 3 rubber hose setup. It however is more prone to leakage failure due to the degradation of the rubber based seal/bore type plungers which are required to force and push the fluid on through the lines to the wheel cylinders rather than just displacing the fluid into the system by the shear metal mass displacement of the metal plunger itself. Thus no doubt the designers of the dual chamber rubber push plunger system deemed it necessary for the need of 2 separate front and rear reservoirs and distribution lines as wear leakage is going to occur on this push plunger system sooner than later.

So in the end, your original setup is actually just as safe as long as you maintain the integrity of your 3 rubber psi lines and maintain/change your brake fluid at least every 2 to 3 years because as mentioned above, brake fluid is an eventual chemical antagonist to rubber compounds even nitrile based rubbers so I am told. To combat against this, either of these type systems should replace the stock rubber based brake lines and have installed in their place D.O.T. approved Teflon lined metal braided brake lines as an additional safe guard from brake line aneurisms and leakage as this no doubt is the most abrupt occurrence that could happen and thereby compromise the entire braking system in fast order. These Teflon lined metal braided lines have their weakness too due to the Teflon itself, so should be replaced every 3 to 4 years to be on the safe side.

This then only leaves the possibility if a metal line or connection should spring a very unlikely leak. More likely a rubber hose breakage or leakage will occur and this will facilitate an abrupt loss of brakes and if that should happen you still have in both type systems your direct mechanical cable based emergency brake system to the rear wheels as a holy mary back-up.

Thanks for the read, buick man. Puts a lot into perspective. My grandfather told me he had the old treadle-vac rebuilt twice before the Dynaflow gave out in '78, and suggested that I also do away with it. The first time was with my grandmother driving the vehicle and the second time with my uncle. The last time it was rebuilt was 2 years before the Dynaflow went out so maybe it was a bad model, I'm not sure.

For anyone curious, I went ahead and ordered the Master Power Brakes remote fill dual reservoir master cylinder and a Speedway Motors 7 inch dual diaphragm brake booster with proportioning valves and residual valves for the drums. I know its not original, I have kept all original parts and accessories, but I want to modernize the system a bit more so I have ease of mind driving my grandfather around in his old Buick. When I get the parts in, I'll post some shots of my setup.

Thanks for the read, buick man. Puts a lot into perspective. My grandfather told me he had the old treadle-vac rebuilt twice before the Dynaflow gave out in '78, and suggested that I also do away with it. The first time was with my grandmother driving the vehicle and the second time with my uncle. The last time it was rebuilt was 2 years before the Dynaflow went out so maybe it was a bad model, I'm not sure.

For anyone curious, I went ahead and ordered the Master Power Brakes remote fill dual reservoir master cylinder and a Speedway Motors 7 inch dual diaphragm brake booster with proportioning valves and residual valves for the drums. I know its not original, I have kept all original parts and accessories, but I want to modernize the system a bit more so I have ease of mind driving my grandfather around in his old Buick. When I get the parts in, I'll post some shots of my setup.

I'm interested to learn how this turned out- did you complete this project? And what year and model did you perform this on?

Yes, how did the project finish? Pictures? I'm thinking of doing this on my 58 Buick.

This was done on a 1956 Buick, as the thread title suggests. The system turned out better than expected. If you buy a new brake line kit, the only two lines that need to be cut and rebent are the one that comes from the T behind the front driver wheel and the one that comes from the rubber flex hose at the drive line. I also had to cut a small hole in the frame of the car for the longer master cylinder to fit in the original mounting position. For the NPT threads on the proportioning valve and pressure residual valves I had to use a T+2 Pipe Thread sealer I got from my local McClendon's Hardware, I could not get the brass NPT fittings to seal without it, no matter how tight I got them. I also applied it to the brass elbow fittings on top of the master cylinder, but they've sprung a leak so I think I'm going to load it up with more sealant since before I just dabbed a spot.

Here are some shots of the build:

Note that the front line I had to redo because the wheel hit it.

Here was the revision, I had to cut a small hole for the master cylinder to poke through the fender well.

Again, not original, but more functional and safe. It won't be a daily driver by any means, but my grandfather told me to throw away the old unit and that was enough for me. These pictures are a bit dated, I don't have any photos of the current state of the system, but I've covered the steel lines in the fender well with plastic wire tunnel so it won't be affected by debris.

Thanks for the update and pictures!  Any idea what the bore of master cylinder is?  What did it come out of?

Thanks for the update and pictures!  Any idea what the bore of master cylinder is?  What did it come out of?

For anyone curious, I went ahead and ordered the Master Power Brakes remote fill dual reservoir master cylinder and a Speedway Motors 7 inch dual diaphragm brake booster with proportioning valves and residual valves for the drums. I know its not original, I have kept all original parts and accessories, but I want to modernize the system a bit more so I have ease of mind driving my grandfather around in his old Buick. When I get the parts in, I'll post some shots of my setup.

It is a 1 inch bore, just like the original system.

Have you road tested this setup yet?  I imagine you will have a very stiff pedal to to the large bore of the new master.