After lots of thought I think I want to mount the master cylinder on the firewall with booster. It just seems to make sense, easier to service and not sure how an under the floor unit will work out with the th350, exhaust, etc. I see speedway has a pretty decent all in one unit for a good price. I have discs on all 4 corners also. Anyone here done this on a 41 or close to 41 ford? Any reason not to? And before anyone says it, I don't care about it not being period correct. I will be driving this car a bunch, it won't see a trailer unless I'm broke down.
I have always heard you need to reinforce the firewall or the flex will cause it to crack. Did one on a 46 Ford and used two pieces of angle iron on the inside of the firewall for the reinforcement over the studs holding the booster then installed the nuts. Ran it that way for several years till I sold it. Took up a lot of space in the engine compartment, can't go too big on the booster or it starts running into stuff.
I know that this information is maybe not appropriate for USA availability but I found that an Aussie VT Commodore master cylinder, booster, and automatic pedal box was a perfect fit into my RHD converted '46 Tudor build. The master cylinder is a fast fill style dual circuit with a built in proportioning valve that can have the spring customised to help balance front to rear braking. The booster is a 10" double diaphragm size that takes up less space in the engine bay. The VT firewall is almost vertical so the master cylinder inclination and the VT pedal box arrangement suits the '41 - '48 sedan's firewall well ..... bonus is that the VT throttle pedal ***embly also bolts onto the VT pedal box and uses a Bowden cable to actuate the carb. I also fabbed an angle iron and square tube sub-frame to support the pedal box and to add re-enforcement between the firewall and the steering column mount under the dash. I'm not sure whether the Aussie built Pontiacs GTO's have a similar arrangement or not. I hope that this info helps some for you.
I would reinforce the firewall from both sides, use something like 3/16" or 1/4" steel I did my Ford from the outside with 1/4" steel plate, still get slight flex, but it stops well.
I use a remote fill MC/booster under the floor of my 40, works super and keeps the firewall looking good.
I have my setup under my driver seat on my '49 and no issues and very easy to service, just make a latch on the floor with small hinges. I am not running a booster, but there is space to add one if need be. The less on the fire wall the better for my build. Either way you go, use 1/4'' plates for any brackets or reinforcements.
On my 41 I did as rusty did, I braced it to the bottom lip of the dash and it reduced the flexing markedly. Use the the smallest diameter booster possible or be prepared to have extra work whenever the driver’s side valve cover needs to come off. Mine has many miles and no sign of cracks in the firewall
Not on a Ford, but I did this on my '39 Chev when I built it. I used a piece of 3/16" thick plate as large as the space inside the firewall would allow to reinforce the firewall. Used a 80's Corvette dual master, and a junkyard pedal ***embly from a Subaru Legacy around 2000. I've used these pedal ***emblies on two other builds because they're cheap, and made to hang on a flat firewall like most old cars have. I made a cardboard template to match the brake master, and pedal ***embly. Then transferred the pattern to my steel plate, and to the firewall to drill and mount it. Once it was fitted, I removed it and added 2.5" to the arm to get the correct manual brake ratio, and welded a 12-20 nut on the end to accept an old Ford truck round pedal to get rid of the rectangle pedal. These are about $30 at wrecking yards for the hanging pedal.
I used a speedway pedal/booster/master on my 46. Has a bar I bolted to the dash/ column mount to triangulate it. Been a bunch of years works slick
I’m leaving mine low. just don’t like the look on the FW Service? I’ve got a lift and floor jack. Stranded on the side of the road? Both locations will if the MC goes bad. Exhaust clearance? I’ve put em under the floor in smaller cars with newer v8s and no issues. Just seems like effort and work not needed and definitely isn’t a visual improvement. This is the current set up I’m working on
On my 47, I used a piece of 1/8" steel, and broke the edge 90* to stiffen it up even more. Installed that on the interior side of firewall, between pedal mount and firewall, and ran a brace to dash. I might have even put a couple tack welds to hold it in place.
I took the master cylinder set up straight out of a 1977 Camaro. I cut the firewall out and welded the whole thing into the 47 firewall. Retained all the Camaro support rods as well. Worked well enough. I ended up with the clutch stuff as well and it all fit pretty good.
Mine isn't a car but it is a 41 and I ran out of room under the truck for the M/C. I don't favor the look of the firewall mount but it is what it is. I started by welding a reinforcement to the firewall. My truck's firewall has a reveal that runs right through the spot that I wanted to utilize so I built the bracket with that in mind. There was a bracket that came with the ***embly but it was cheezie and I am not. 4 pieces of 1" inch flat stock welded together, drilled, trimmed and then welded to the firewall. I modified the hanging pedal bracket (weld in studs) prior to powder coat so that I could run a U channel brace I fabricated, running from the pedal bracket to the steering column-drop mounting bolts. This a bolt in brace to make install and removal a bit easier. You can also see in the picture another U channel that is welded in to brace the center dash and support the new cowl vent motor. You cannot brace a dash enough if you are hanging the column from it. I did not use the two lower mounting holes in the bracket as this was firm enough without drilling more holes in my firewall. The 4 speed Mopar automatic poking through the floor was the cause of the relocated master. The finished product, like I said above, is what it is. Not my favorite look and if I was running a hoodless car I would have not done this. If I was running a 4 speed manual, I would not have done this. But there was just no room in the inn, so to speak. There probably easier ways to do it but this was my way. Brake components are CCP, I have used them for decades on F body GMs and they are a good package and are available chrome plated including the proportioning valve and it's bracket. I hope this was helpful.
The Subaru pedal ***embly I used already had a dash brace, so all I had to do after bracing the firewall was to make a plate to go from the existing brace to the dash.
If you get the correct MC for 4 wheel disc brakes and have a pedal ratio of 6 to 1 there is no need for a booster. I believe a 7/8” Master will do it. I would inquire brake system manufacturer like Wilwood and ask a tech. I’m not a fan of boosters on a firewall because I believe they are just **** ugly.
The booster hanging on the firewall looks terrible although it is probably not that big of an issue with a car with a full hood. If you have room under the dash have you considered a 90 degree under the dash M/C and booster? Speedway and others sell a 90 degree bracket and you can add your own M/C and booster.
Well, I wound up getting the adapter flange and put it under the floor. Only thing is I will need to cut a hole in the floor which is no big deal, except I have to cut the floor brace in half. It's exactly over the rear bale on the MC to where I can't even open it up while it's on the car. I think I will make a new brace directly behind that from the frame to the x. Especially since I'm using bucket seats. I have all my lines bent up and ran with residual valves and a proportioning valve inline for the rear.
This thread has some more info to add to what @36cab posted. https://www.jalopyjournal.com/forum/threads/under-dash-brake-setups.1089300/ Although this is closer to what I was thinking https://www.ozerodsshop.com/product/disc-brake-seal/
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