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under floor duel power brake install...help needed
hey guys, spring is around the corner and my first project is an under floor duel power brake install. i'm sure this has been discussed here many times but i tend to suck with the search function so are there any good step by step instructions out there.
thanks
mike
My word of advice...don't use an under the floor brake system. Here are the problems associated with it. The 7 inch booster is too small to be effective, the filler hole in the floor will have to be moved, it may interfere with the brake/clutch pedal, it will interfere with the exhaust system, and you will have to run inline residual valves to prevent fluid running back to the MC. There may be others but that's all I can think of right now. Put the MC on the firewall and avoid all those problems. If you are thinking about a floor mounted MC, then you are probably wanting a clean firewall but the elimination of all these problems is worth a little firewall clutter.
Actually my underfloor booster works quite well on my disc/drum system. If it is weak then you probably need a vacuum canister and in extreme cases with wild cams you may need a vacuum pump like most new model vehicles have. But if you have low vacuum you would probably need this with a firewall mounted booster also. And the solution for for the filler hole fit is a translucent remote fill tank mounted on the firewall. And if you purchased a disc/drum booster/MC then the residual check valve should be in the proportioning valve port to the rear drums.
Hanging pedals require the purchase of the pedals and sled and also the firewall should be reinforced to prevent stress cracks.
Either solution is good and is far safer than the single chamber MC that was OE.
In answer to your question: It’s much easier to install with the cab off. I am not implying you HAVE to take off the cab. You also might want to clean the frame and paint it while the old master is out. I agree a remote filler is nice, but you aren’t ,or shouldn’t be, adding fluid that often. I also agree you should buy a kit for what you have, drum/drum, disk/drum or disk/disk. Having cobbled one together it’s by far cheaper AND you are pretty sure everything was made to work together. You also need a different kit if you have and will be keeping a manual transmission. Most kits are set up for automatics. I would suggest running all new brake lines if yours are original. It’s hard enough to install a power master but to have to get back under the truck and track down leaking lines isn’t worth the extra $$$ for new brake lines. (You can actually use pre-made lines) Also pop for a new brake switch while you’re at it. No telling how old the one you have on the truck is and again it’s cheap insurance that you’ll have no leaks. You’ll need a vacuum source. Depending on your engine and carb this may or may not be an issue. If you don’t have a port large enough you can get a spacer that goes under the carb , between the intake manifold and the base of the carb. Don’t skimp on Vacuum line. Make sure the hose you buy is rated for vacuum not just a heater hose.
That should be most of the pitfalls to avoid while installing a under the floor master and booster.
Good Luck and once you’re done there will be no more standing on the brakes to get stopped.
I have been using the under floor booster on the wife's 52 for a couple years and 5000 miles. Disk/Drum, no residual valves as it has a combination valve. Remote reservoir on firewall. Only problem is they are are powerful and you can't rest your heel on the floor when braking so sometimes get more brake than intended.
Not sure why so many are against the under floor MC/booster setup. To me it leaves the engine compartment much cleaner and if you use the correct components it works very well. My 53 has the complete system from a '87 Lincoln except for the 7" booster from a BroncoII and if the brakes worked better I would be constantly wiping nose prints off the windshield. I have put over 90K on mine since finishing the build in '08 and have yet to add any fluid, so to me the remote reservoir is not necessary.
Not sure why so many are against the under floor MC/booster setup. To me it leaves the engine compartment much cleaner and if you use the correct components it works very well.
Right you are!
I have a 2005 F350SD hydraulic booster and 1.5" dual-circuit master cyl in my 55 F-600. I don't have power steering so I still have to have a PS pump but it's going to work great and I get to use the original pedal!
I put the Corvette dual master cylinder with a Mustang 7" booster on my 1954 when I was building it (2012). Not one problem after 15,000 miles and I have yet to add any brake fluid even though I do have a nice billet remote reservoir. As mechmagn stated if my brakes were any better I couldn't stand it. I have discs all around and manual regulator mounted on the frame to adjust pressure going to rear wheels. All 4 wheels lock up at the same time and no pulling right or left. In short, I am well pleased and my firewall is nice and uncluttered. Also my distributor is in the front (351W) so no problems there either! Go for it, Steve
PS Rimrock F1 and Pete, y'all have really nice looking set ups on yours!!!
Does anyone have any suggestions on residual pressure valves? It looks like my MC is about even with my calipers but the brake lines loop up above both. I think I will need three valves since I'm using the CPP kit that has an individual line from the prop valve to each front wheel.
I blocked one of the front holes and ran my front lines like they were original. There are mixed reviews with or without residual check valves. I added them mainly because I didn’t want that feeling if I didn’t have brakes.
I mounted the MC under the floor in my F4. It works very well. I did cut an access hole further back on the floor to fill it. I used Wilwood residual pressure valves, IIRC, 10lb for the rear drums and 2Lb for discs, and a Wilwood proportioning valve that I ordered from either Summit or Speedway. You will need the RPVs if you leave the MC under the floor, unless you find a MC with them built in. The original MC has one. You will also need the prop valve if you add disc brakes to the front.
Mark
Usually the CPP kits have a residual check valve inside the proportioning valve mounted under the assembly, but you might want to ask them about yours as I bought mine a few years ago.
CPP description on eBay (description at the bottom is good but doesn't really say).
great advice guys, the kit came with the residual valves but going with the remote filler looks like the way to go. the engine it a 429 with a stock sounding cam so i don't believe vacuum will be an issue.
taking the cab off is an option so by looking at it the gas tank will need to come off, looks like a good time to relocate.
gotta love it when one project leads to another.
Does anyone have any suggestions on residual pressure valves? It looks like my MC is about even with my calipers but the brake lines loop up above both. I think I will need three valves since I'm using the CPP kit that has an individual line from the prop valve to each front wheel.
I spoke to CPP about residuals since my calipers are above the master, they told me since I was using a combination valve they would not be needed. Also if you use a remote reservoir that is above the calipers it will provide the same pressure in the system that the master would provide if it was firewall mounted.
01-25-2018, 06:59 AM
It’s much easier to install with the cab off. I am not implying you HAVE to take off the cab. You also might want to clean the frame and paint it while the old master is out. 
I agree a remote filler is nice, but you aren’t ,or shouldn’t be, adding fluid that often. 
I would suggest running all new brake lines if yours are original. It’s hard enough to install a power master but to have to get back under the truck and track down leaking lines 
isn’t worth the extra $$$ for new brake lines. (You can actually use pre-made lines) 
Also pop for a new brake switch while you’re at it. No telling how old the one you have on the truck is and again it’s cheap insurance that you’ll have no leaks.
You’ll need a vacuum source. Depending on your engine and carb this may or may not be an issue. If you don’t have a port large enough you can get a spacer that goes under the carb , between the intake manifold and the base of the carb.
Don’t skimp on Vacuum line. Make sure the hose you buy is rated for vacuum not just a heater hose.
feeling if I didn’t have brakes.
