I truly appreciate your guys imput on this, but to be honest with ya, I'm really confused more than before. I've always had a phobia about brakes anyways. I know the disc conversion isn't doing me any good sitting on the floor of my garage. I need to install a new master cylinder and completely redo the lines, basically a complete brake overhaul. I just want to do it correctly the first time, especially with brakes!!!

 

I hear you imlowr2, but those new parts wont do you any good on the floor. Good luck.

 

[QUOTE=imlowr2] This is scarey, because I just purchased the disc kit from Classic performance parts. I haven't install the kit yet because I'm still looking for a master cylinder with dual chamber. I'm not sure if the kit comes with the proportioning valve, or did you purchase that separate? According to CPP, you don't need a proportioning valve, however everyone tells me with disc in the front and drums in the rear[QUOTE]

Ed, do you have just the disc brake wheel kit from CPP? Are you going to mount the master cylinder in the stock location under the floor or on the firewall? Are you going to use power brakes or manual? Get a catalog from MidFifty F-100 Parts. They have a good simple diagram of the parts needed to convert to disc brakes. They also sell power brake conversions and manual master cylinders pre-valved or no valves.

You will definitely need a proportioning valve and residual check valves when using front disc and rear drum brakes, power or manual. I prefer to use the adjustable prop valve. It goes in the rear brake line. Residual check valve for discs is 10 lb and 2lb for rear drums.

You can do this! If I can, anyone can.

 

Roy,
Do you have the proportioning valve in the rear brake line?
Bruce

 

George, you've helped out countless people here on the site and I have been one of them on many occassions. But, I have to call into question your statement about pressure versis diameter. Maybe I just misunderstood your meaning. My logic is: Force equals pressure times surface area. IE: 1000 psi on a 3 square inch surface generates 3000# force, while the same 1000 psi on a 2 square inch surface equals 2000# force. So, I believe that small pistons require more psi to generate the same stopping force as bigger pistons. Or, are we saying the same thing? If I'm all screwed up here, be kind. Jag

 

John,

I think we're saying the same thing, you're working at the wheel cylinder and I'm working at the master cylinder.

From the master cylinder side, if you need 1000 psi in your brake system, and you have a 1 square inch piston area, then you'll need 1000 lbs of force from your leg or the booster on the master cylinder piston to get the 1000 psi. If you decrease the size of the piston to 1/2 square inch, you'll only need 500 lbs of force from your leg or the booster (500 lbs = 1000 psi x 1/2 in squared). Keep in mind that you'll be moving only half the fluid though with the small master cylinder bore - ya don't get someting for nothing.

At the wheel cylinder end, if you need 1000 lbs of force on the brake pads, and you have 1000 psi in your brake line, then you need a caliper with a 1 square inch area piston. If you decrease the piston area to 1/2 square inch, you'll need 2000 psi to get 1000 lbs out of the caliper (1000 lbs = 2000 psi x 1/2 in squared).

Hope this makes more sense.

 

Alright George, yu da man. I got it that time. Jag

 

Earl, I just want you to know that mathematics was not my best subject in school (smile). However, I did understand your explanation. So... now that I'm installing a new disc brake conversion kit and have absolutely know idea of how many pounds of pressure it takes, what do I need to make them work? Does this sound like I'm really confused or what? I can tell ya, that when I push down on the brake pedal, my truck stops pretty nicely and I don't see any leaks anywhere. LOL.... I'm really considering having a professional do this project. I can only imagine the cost of install, running new plumbing (which it really needs bad) and a new master cylinder. I've done all the work myself so far, but this one might stump me.

 

Correction, got the sizes backwards in previous post.

You will definitely need a proportioning valve and residual check valves when using front disc and rear drum brakes, power or manual. I prefer to use the adjustable prop valve. It goes in the rear brake line. Residual check valve for discs is 2 lb and 10 lb for rear drums.

You can do this! If I can, anyone can.

 

Here is a link to a simple diagram for front disc and rear drum brakes for the valving. http://www.clubfte.com/users/rogerf100/BrakeSystem.jpg

 

Your reading to much into the project, just install the kit take the truck out on a deserted street, cram on the binders if it don't stop properly then it's time to troubleshoot. All, or most of us guys on this forum are just R&D (Research and development) techs. We sometimes fall and skin our knees, get back up and go some more.

 

Ed,

I can do the calculations, but as the other fellas have said, that's different than puting together a brake system from parts. If you have a kit that was designed by someone that knows what they are doing, you should be fine. Follow the directions and, if you get stuck, ask here - or better yet, get on the phone with the manufacturer. They can tell you things like "No, you don't need a proportioning valve or residual pressure valves because we include them in our master cylinder". Or "Yes, buy a 10 psi residual pressure valve and put it in the rear lines to the drum brakes.

I've been there, when I thought a project was over my head. My first idea is usually to go read everything I can find about the system. I throw away the crap that is confusing, and focus on reliable information that makes sense. A reasonably intelligent fella like you can get all the information you need with some studying and a phone call or two. Roger has a pretty straightforward diagram that should get you 90% of the way there.

 

Since I'm not the one to quit or pass up a challenge against myself. I'm going to give the brakes a go. and if all fails, I can go to my neighbor who recently did his brakes on his streetrod. LOL....
Roger- Thanks for the diagram, I'll be using it. I'll let you guys know how it goes....
Ed

 

Ed what kind of brake line tubing are you planning on using steel, or stainless. Are you going with hose, or steel braided lines. If you are using that steel inner bearing adaptor besure to warm it to 400 degrees prior to installing it. The heat will expand it and it should go on with a few light taps. It can be a nightmare to install cold.

Rod

 

You know brucewolff I dont really know the internal make-up of this valve that I got from classic performance. I just connected as advised on the instruction sheet. By the way I just got the head on my truck and the brakes work fine on the road after shorting that master cyclinder push rod. Go figure. Roy.