Topic: 47 1-ton dual master cylinder conversion

chiefe9	-- 08-25-2010 @ 2:22 PM
	I'd like to convert from a single to dual port master cylinder and booster on my 47 1-ton truck that still has the original complete brake setup. Naturally, I'd like to have power brakes but will settle on attaching a dual master cylinder only if that's my only option. Bob Drake sells a conversion adapter (item EC-415)that supposedly attaches to the 3-bolt original attachment allowing use of a Mustang or Corvette dual master cylinder. Anyone know if this works on a 1-ton? Any other recommendations and or solutions will be greatly appreciated! Hopefully, one of you has already done this. Ha! (picture shows current master cylinder bolt pattern)
49fordv8f4	-- 08-25-2010 @ 7:01 PM
	I was interested in making the same change on my 49 F4 (1 Ton) truck. It uses the same master cylinder as your Tonner. My front brakes are the same as your rear brakes also. The rear brakes on my truck use an even larger wheel cylinder than yours. I said all that to tell you this, the problem with adapting a dual master cylinder to our larger trucks is the master cylinder volume. The kits you find are for a 1/2 ton truck which uses smaller wheel cylinders than our trucks therefore require a smaller volume of fluid to operate. You would probably have less trouble finding a master cylinder than I would as your wheel cylinders are smaller than mine but it would not be a bolt on replacement. A master cylinder from a late 70's or newer Ford F350 might work for you but it would take some modification to the truck to make it work. I went to my local parts house to find one for my truck. The only thing I could find that I could adapt was for middle 80's or later F600-F750 with hydraulic brakes but a rebuilt cylinder was going to cost $300.00+ so I rebuilt the original one. Sorry for the rambleing but I don't think a bolt on replacement master cylinder is available for anything larger than a 1/2 ton. The bolt pattern is also larger on our master cylinders than a 1/2 ton-passenger car master cylinder. You can add a Bendix Hydrovac or a Midland Diaphram booster to your truck for power brakes. They were optional on the larger trucks and would work well on your truck. I'm adding one to my truck. I hope this helps. Mark Poley
supereal	-- 08-26-2010 @ 10:15 AM
	Mark is correct about master cylinder volume. Converting a single master to a dual involves replumbing the system to include a proportioning valve. There are boosters available from vendors such as Chassis Engineering (www.chassisengineeringinc.com), and I suspect Dave Wilton has some ideas as well (www.MTcarproducts,com). Most light truck owners are looking for the safety of dual systems, rather than brake power, and simply adding a booster won't do that. Brake systems have to be carefully engineered, and "homebrewing" can cause more problems than it solves.
alanwoodieman	-- 08-27-2010 @ 10:43 AM
	I have a 41 3/4 ton and installed a dual master cylinder from a Ford pick-up, 1968 which was first year to have dual master cylinder and also drums brakes front and rear. a 3 hole to 2 hole adapter was used. 68 master cylinder had 2 slotted holes which had to be trimmed to fit the brake pedal bracket. So far seems to work pretty good. Rebuilt master cylinder was around $35 plus cost of no core to return.
chiefe9	-- 08-29-2010 @ 3:52 PM
	Thanks everyone for replies. Good "food for thought". I'm still researching. Hope to go to the "Shades of the Past" show in Pigeon Forge week after next. Maybe someone will have made the change.
alanwoodieman	-- 08-29-2010 @ 5:57 PM
	some ford products, 55-57 t birds for one used a remote mount vacuum booster that is avaiable repro and can be mounted in just about any location, inside the frame rail would be a good choice, but if you go to a dual master cylinder you definitly need to use a proportioning valve or you would definitly lock up the power assisted shoes
TomO	-- 08-30-2010 @ 8:49 AM
	My understanding of the brake system is that if you have drum brakes at all 4 corners and you have a master cylinder for drum brakes, that a proportioning valve is not needed even with a dual master cylinder. The proportioning valve was developed to eliminate the differences between drum rear brakes and disc front brakes. In a panic situation, the rear drum brakes would lock the wheels fast than the front disc brakes, making the vehicle hard to control. With a dual master cylinder, you should also install a pressure differential switch to signal you when you lose pressure on one of the ports of the master cylinder. Here is a link to an article that explains the purpose of the proportioning valve, pressure differential switch and the combination valve. http://auto.howstuffworks.com/auto-parts/brakes/brake-types/master-brake2.htm Tom
supereal	-- 08-31-2010 @ 7:06 AM
	In theory, that is true, Tom. If the two parts of the master are balanced, no problem. If not, or half of the system loses pressure, a proportioning valve can lessen lockup and loss of control. At our shop, we see quite a few leaking brake systems because the heavy winter road salt causes line perforations. I'm not sure which is more dangerous: losing all or half the braking. We don't do brake conversions due to the liability factor. If I was going to modify my brakes, I'd opt for a disc/drum conversion. That would eliminate the usual drum brake fade in heavy traffic situations.

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