55.2-59 Brake booster (2 part Q)

[regan56]

Good day!

back in teh day i got a bit ahead of myself and purchased a bunch of parts that i wanted for my 56. one of these parts was the underframe brake booster and MC. i go on my merry way and re-start my build after a long halt due to life and kids and whatnot.

i go to finally install my brake system over this holiday break and find that my trans cross-member is directly in front of where my new booster will go. F*** me! well, kinda..TBH i wasnt really all that excited about it as i had kinda wanted my brake pedal to be a hanging set-up anyway, so i was bummed, but not torn-up about it. im more pissed that i spent $$$ on it and now cant use it. And at this point revising the trans mount is not an option im willing to explore.

so i now have the Speedway 55-59 frame mount kit in my garage sitting on my workbench.

Which brings me to my 1st question. i know i can re-use the MC, but the booster is rear facing (a pusher), can i modify it in anyway to be a front facing (puller) on my firewall? or am i totally not getting how these work and they can work in either direction?

2nd Q..if the above cannot be used in a firewall mounted situation, i need to go out and get a new setup. I'm running front discs, rear drums (81 Camaro). is a dual or single diaphragm better? 7" or 8"?

[dsraven]

a hydroboost works really well whether frame or firewall mounted. they require a pressure and a return line to the power steering pump but they are very relioable as far as boost and also quite a bit smaller so tidier, in some respects (there are those hoses).
a vac operated booster usually uses a pivot to operate the acutal booster section so, depending on the mount of the actual booster to the mounting bracket, i am sure you could make it fit to a new bracket for firewall mounting. post up a few pics. if you look back you may see the booster was from a firewall mount originally and simply remounted to the new frame bracket (usually there are 4 mounting bolts). small boosters like the ones sold for frame mount kits are usually a dual diaphragm style to allow the same amount of square inches of surface on the diaphragms for the vacuum to work on.

[leegreen]

vacuum boosters all work the same. vacuum on the master side of a diaphragm, atmospheric pressure on the pedal side and a valve

https://help.summitracing.com/knowle...SR-05293/en-us

[regan56]

ya, i thought of a hydroboost, and maybe still will if i cannot re-use the pieces i have. all it would take is just a tee in both of my PS lines. I'm still running the OG straight axle with a PS conversion kit so no rack to steal from.

yes the bolt up to a FW mount is certainly achievable, with the proper mount of course...my question was more the operation of the booster's diaphragm. does it matter which way the diaphragm moves? does it operate the same whether I'm pushing the diaphragm or pulling on it? (does a FW kit have a different dia then a frame mount??)

[regan56]

Originally Posted by leegreen

vacuum boosters all work the same. vacuum on the master side of a diaphragm, atmospheric pressure on the pedal side and a valve

https://help.summitracing.com/knowle...SR-05293/en-us

ok, so no matter which way it faces...

[nvrdone]

its my understanding that a brake booster only works one way. when you push the pedal, the rod goes in pushing the diaphragm in causing pressure in the m/c & lines. I've never seen a booster that pulls the rod out and causes the needed pressure. I did see a setup where the m/c & booster were mounted under the dash but that had a bell crank and other linkage to make it work.
Some one correct me if I'm wrong on this.

[regan56]

Originally Posted by nvrdone

its my understanding that a brake booster only works one way. when you push the pedal, the rod goes in pushing the diaphragm in causing pressure in the m/c & lines. I've never seen a booster that pulls the rod out and causes the needed pressure. I did see a setup where the m/c & booster were mounted under the dash but that had a bell crank and other linkage to make it work.
Some one correct me if I'm wrong on this.

EDIT..i see it now..THX all..

[dsraven]

here is a link to how a basic vacuum brake booster works
https://www.google.com/url?sa=t&sour...6GYX5O0ctDQ_GD
yours is likely from a corvette or something that had no room for tge booster so they used a dual diaphragm style. anyway, take the pin out of the pushrod to disconnect the rod from the booster from the rest of the assembly, then unbolt the booster from the frame bracket part and youhave the basics for your firewall mounted booster. some will use a direct mount to the firewall at this point, so a large hole for the booster's pushrod and valve body to slip through, with 4 smaller holes surrounding that to bolt the unit to the firewall. it is recommended to reinforce the area of the firewall around that spot to help stop it from flexing, which causes cracks. most "hung" or hanging pedal assemblies will bolt up to the same bolts that hold the booster onto the firewall and this will help with that and also keep the geometry/dimensions between the parts ike they are meant to be. the other end of the pedal assembly, closest to the driver, is usually attached to the rear part of the dash, where the steering column drop bracket is bolted down. it kinda goes without saying that since the firewall and dash were not made to support the load that a brake booster and pedal assembly can place on the relatively flat firewall it is a good idea to build or purchase a kit that is going to spread that load over a larger area. imagine sitting in the seat and pushing as hard as you can on the firewall, simulating the force you would apply if doing a panic stop.
here is a link to a pretty standard set up for a 55-59
https://www.performanceonline.com/19...e-Booster-Kit/

on my 57 I am using the pedals, booster and master cyl from a 2004 gmc envoy. the system has a big bubble shaped formed sheet metal bracket that bolts onto a large hole in the firewall and this is what the entire brake pedal, accel pedal, booster and master cyl system is bolted to. since the sheet metal part is a bubble shaped part it really helps strengthen the firewall there. the steel bracket that holds the brake pedal (they only came with auto trans) also holds the accel pedal for drive by wire. the "inside the truck" pedal bracketry in the stock formation is actually a couple of parts that would be really easy to modify to make fit into a lot of different projects. one wouldn't really need to use the bubble shaped sheet metal part if you don't like to cut a big hole in your firewall to accomodate it and the extra space you would lose under hood from the bubble. the steering column also feeds down through a bellows in the bubble. I will see if I can find a pic

[dsraven]

here is what it looks like out of the truck from a wreck I salvaged.
other vehicles have something similar that may work for you as well. a trip to the local wrecker would maybe help you visualize it all.

[regan56]

Originally Posted by dsraven

here is a link to how a basic vacuum brake booster works
https://www.google.com/url?sa=t&sour...6GYX5O0ctDQ_GD
yours is likely from a corvette or something that had no room for tge booster so they used a dual diaphragm style. anyway, take the pin out of the pushrod to disconnect the rod from the booster from the rest of the assembly, then unbolt the booster from the frame bracket part and youhave the basics for your firewall mounted booster. some will use a direct mount to the firewall at this point, so a large hole for the booster's pushrod and valve body to slip through, with 4 smaller holes surrounding that to bolt the unit to the firewall. it is recommended to reinforce the area of the firewall around that spot to help stop it from flexing, which causes cracks. most "hung" or hanging pedal assemblies will bolt up to the same bolts that hold the booster onto the firewall and this will help with that and also keep the geometry/dimensions between the parts ike they are meant to be. the other end of the pedal assembly, closest to the driver, is usually attached to the rear part of the dash, where the steering column drop bracket is bolted down. it kinda goes without saying that since the firewall and dash were not made to support the load that a brake booster and pedal assembly can place on the relatively flat firewall it is a good idea to build or purchase a kit that is going to spread that load over a larger area. imagine sitting in the seat and pushing as hard as you can on the firewall, simulating the force you would apply if doing a panic stop.
here is a link to a pretty standard set up for a 55-59
https://www.performanceonline.com/19...e-Booster-Kit/

on my 57 I am using the pedals, booster and master cyl from a 2004 gmc envoy. the system has a big bubble shaped formed sheet metal bracket that bolts onto a large hole in the firewall and this is what the entire brake pedal, accel pedal, booster and master cyl system is bolted to. since the sheet metal part is a bubble shaped part it really helps strengthen the firewall there. the steel bracket that holds the brake pedal (they only came with auto trans) also holds the accel pedal for drive by wire. the "inside the truck" pedal bracketry in the stock formation is actually a couple of parts that would be really easy to modify to make fit into a lot of different projects. one wouldn't really need to use the bubble shaped sheet metal part if you don't like to cut a big hole in your firewall to accomodate it and the extra space you would lose under hood from the bubble. the steering column also feeds down through a bellows in the bubble. I will see if I can find a pic

great stuff here...thank you.

[dsraven]

here is a pic installed. please dont be too critical of the surroundings as things are far from finished in that pic. it gives you an idea of what it looks like with the larger booster though.

[Rickysnickers]

I'd be ashamed to post that photo Dennis!! Look at all that clutter!!!! LOL, just kidding

[dsraven]

Yup, hadta think hard before I let myself hit post. Haha.
I'm starting at the rear of the truck and working forward. Finishing everything down to a final coat of epoxy. I'm at the back of the cab now. So many other things in life come along to interrupt.