Brake conversion & proportioning valve

[Cbumpus9398]

Good morning. I have a great 72 f100, 2 wheel drive that I have decided to restore. It originally had all drum manual brakes. I have found a 75 donor truck. I bought the entire front end, I-beams, spindles, rotors, calipers, radius arms, master cylinder/booster and proportioning valve. I have replaced all the king pins, bushings, turned the rotors, cleaned the calipers and have it all together and it looks greats. The booster appears to have the wrong push rod. I plan to purchase a new combo and use the old one as a core. The new one has an adjustable push rod. My question is, do I have to change the valve? As I look under the truck, under the driver side frame, there appears to be a proportioning valve already in the system. I'm sure it's an original 72. Will it work or do I have to change it or do I leave it and add the 75 valve? Actually, do I even need to add the booster? With the front disc brakes, will it make that much difference, to add the booster? The intent was to convert to power brakes and I still want too. I just need some advice on where I am at this point. Please help-thanks-Charlie

[BobbyFord]

Use everything from the '75. The '72 has a distribution block, not a proportioning valve.
Yes, there's a big difference between power brakes and non-power brakes. I would use the booster.

[Cbumpus9398]

Great thanks but would the distribution block have an electrical connections to it? This has a wire connected to the valve?

[HIO Silver]

Great thanks but would the distribution block have an electrical connections to it? This has a wire connected to the valve?

The electrical connection is for the brake warning light... it allegedly comes on if either the front or rear brake circuits fail.

IMO, it's today's equivalent of a 'check engine' light.

[Cbumpus9398]

Ah that makes sense. Thank you. So, should I use the 75' or should I try to get a new one?

[Cbumpus9398]

Proportioning valve-that is.

[BobbyFord]

It's up to you. I don't know what your budget is.
I just converted my '72 over to disc. I used '77 spindles, calipers and rotors with aftermarket master/booster and prop valve.

[Cbumpus9398]

I can get an original 72' reman master/booster for just over $100.00. Will it fit alright and function right? I Assume power brakes were an option in 72'

[BobbyFord]

You need a disc/drum master. 72 is a drum/drum master.

[flyboy2610]

Actually, do I even need to add the booster? With the front disc brakes, will it make that much difference, to add the booster? The intent was to convert to power brakes and I still want too. I just need some advice on where I am at this point. Please help-thanks-Charlie

Here is an article that explains how drum brakes operate. Due to their design, they are 'self actuating'. This is a fancy term for "during operation they try to wedge themselves against the drum, thereby increasing stopping power."
http://auto.howstuffworks.com/auto-part ... brake1.htm

Disc brakes do not have this feature. They depend solely upon the amount of pressure exerted by the pads against the rotating disc to stop the vehicle. You will never be able to exert, just by leg pressure, the same amount of pressure that a brake booster will be able to supply. CAN you get by without a booster for disc brakes? Yes. Will your brakes be nearly as effective as if the booster were there? No. So if you go discs, you really want to add the booster.

[ultraranger]

Explanation of the two valve types (drum/drum and disc/drum) how they function, and the purpose of the plastic switch sticking up out of the valve body.

http://www.ford-trucks.com/forums/12674 ... st14873379