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I have a 1973 Scout II that I had front drum brake and converted them to disk. I did not install a power booster, and installed a new stock master cylinder. the problem I am up against is I have no peddle at all. I am wondering if I should purchase a master for a 1974 scout II with disk brakes cause the reservoir for the front brakes is bigger in that master or any one have any suggestions or have ran into the same problem as I am having? thanks        

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Scoutt73...I'm a strong proponent of comparing equipment on a complete donor vehicle.  For disc brake conversions, I am concerned about the master cylinder piston displacement, reservoir capacity and bore diameter.  Did you use '74 Scout II parts for the conversion?

I also want the proportioning/combination valve to match the disc front brake/drum rear system.  I like your idea of using a '74 Scout II as your prototype for matching parts.  The only additional concern is the size of the rear brakes (drum).  If the same (shoe size and wheel cylinder bore size) between your '73 and the '74 disc brake/drum brake models, you should have it.

Catalogs list the bore sizes for master cylinders and wheel cylinders, but as you suggest, you're also concerned about master cylinder reservoir size and fluid volume (piston/bore diameter) available with each push of the brake pedal.  You need to use a disc/drum application master cylinder.  

I'd consider a booster at the same time and adjust the booster pushrod with care and by the book.  Again, you need to compare all the parts on a '74 booster/disc front brake application, everything from the brake pedal through the booster, master cylinder, combination valve and tubing size.

Moses

 

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thanks for your input Moses, I am going to install the proportioning valve that matches up with the 74 scout II Master cylinder and I am hoping that will do the trick.

will let you know how it turns out. thanks again for your input.

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Scoutt73...You're installing the '74 disc front brake/drum rear brake master cylinder, right?  You need a disc/drum master cylinder to assure enough bore size (piston displacement) and reservoir capacity for the retrofit disc front brake calipers.  Glad you're changing the proportioning/combination valve.  The calibration for disc front brakes is different than drum brakes.  

Be sure that the pedal pushrod is adjusted properly for the '74 master cylinder's piston to retract fully with the pedal released.  Bleed all four wheel brakes and make sure that each wheel brake applies pressure when you're done.  It can be tricky getting the brakes to bleed without tripping the safety valve and blocking out the brakes at one end or the other.  

Let us know how this turns out and whether you have the pedal and braking capacity you need.  If the pedal pressure required for stopping is not to your liking, consider a booster...

Moses

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