Has anyone ever tryed putting on a disk brake master cylinder on a drum brake system. I know that you're brakes will suck if you have a drum brake master cylinder on disk brake system. But I can't find any info on putting a disk brake master cylinder on a drum brake system. Anyways I put one on my 65 F-250 and I popped the master cylinder. I'm not sure why it happened. Any help would be appriciated.

 

There is only one problem with what you are asking. If you have a disk/drum master cylinder, there is only one check valve installed, for the drum side only. On a 4 wheel disk setup ther would be no check valves installed. The little valve retains about 5 to 8 pounds of pressure on the system to keep wheel cylinder cups seated against the bores. Aside from this, all master cylinders are basically the same. You can install or remove the check valve depending on the specific application given. Check valves used to come seperate with master cylinders to install when applicable. But nobody knew or cared to "follow the inclosed instructions". Famous quote from an unknown DIY mechanic; "You dont need that little gismo. I have never used one" Guess you can figure out what happened after that.

 

So do I need to put in a valve on the front resivior also? Is the valve you are talking about a residual pressure valve? I ordered another master cylinder for a 78' F-150 tonight, it will be in tomorrow. I need to know if I need to get a residual pressure valve for the front line or not. Since I have my master cylinder off I am also going to add the brake booster.

 

Unless things have changed over the years, that valve used to reside under the brass seat for the brake line. I believe you used a mqchine screw, if the small hole is threaded, and draw out the brass seat. The valve just slides in and you carefully tap the brass seat back down. mThis was normal practice back in the olden days. You ask a "certified brake specialist" today, they might suggest you dont have a clue, or they dont, about what you are talking about.

 

You will need a residual valve. This valve looks very similar to a control/proportioning valve used on disk/drum systems. It accommodates both lines from the dual chamber master, provides dual line capability to the front (like a disk system) and one line to the rear. It may also have provisions for a system failure warning light. My truck had an aftermarket valve on it and dual chamber MC with a 1" bore with an 8" booster power assist drum/drum. I would use components for a later model drum/drum truck with dual chamber MC. Adding a 8" booster is easy. I think if you add a 9" booster you will have really touchy brakes. Buy the catalog from www.mcbrakes.com This catalog is actually a "how to" manual that provides excellent advice. I have the a 8" booster and valve that came off my truck. Shoot me an e-mail if you want to try that.
William in Atlanta

 

Just don't get too happy about your newly installed power brakes until you make sure you have very good drums. I mean the kind that haven't been turned several times and made thinner. Power boosters do just that, they apply a lot more power to the drums than what they have ever been used too. If you don't have some very good drums you will wish you had never installed new floor pans because you may have to pull a Fred Flinstone with feet sliding on the ground to try and get your truck stopped should you pop a drum. I'm not going to include the name of the person that knows this from a personal experience. Good Luck