Herr Otto

Rustyzman, I emailed you the info. Thanks, Otto

I opted for the dual chamber master because I already had to get a new master cylinder and I figured why not go with what is considered safer. With a dual master it is like having a back up system if one of the chambers goes out. This is less than ideal but it is better than having no brakes at all. Since 1968 any vehicle manufactured in the U.S. has to have dual chamber master cylinders. I also will most likely will not be doing much if any expressway driving. The previuos owner already switched the brake pedal to one from a 1965 Coronet, therefore the master was now mounted on the firewall instead of the frame. This master was the type with 4 mounting bolts. I had to drill two different holes for the new NAPA master shown in the picture. This is probably the first time I feel that I can actually contribute to this forum instead of always asking for help.

The NAPA master is UP36359. I believe this has finally taken care of my braking problem. I have a good pedal and the rear brakes stop the wheels from rotating when jacked up and in gear. This was very painstaking as I had tried 4 different master cylinders. Here is what I learned: 1. On a manual master cylinder with 4 drum brakes, the chambers will be equal in size, their chambers are also smaller than power brakes. 2. Typically but not always, the chamber closest to the firewall will be for the front brakes. 3. Drum brakes require a 10 lb. "Residual Valve" either built in the master or external ones can be added. Rebuilt masters will not have these valves built into them, only "NEW" masters will come with them built in. The purpose for the "residual valve" is to keep pressure on the brake shoes so they do not have as far to travel, elininating a soft feeling pedal and pumping of the brakes. 4. The original master on my truck was a single chamber with a 1 1/4" bore. My "New" dual chamber has a 1 1/4" bore and the residual valves built in it. I purchased 2 external Residual valves that I ended up not needing. If anyone is interested in them I will sell for the price I paid plus shipping. $9.95 ea. plus shipping. They were never put on the truck. Thank you all for your help, Otto

My question is , which chamber should feed the rear brakes and which one for the fronts?

After much research and speaking to people from master power brake and NAPA, I purchased this http://www.napaonline.com/Search/Detail.aspx?R=UBP36359_0270674277 master cylinder from NAPA. My problem now is determining which is the front chamber and which is the rear. The master cylinder is for manual brakes and each chamber is the same size. The threads going to the front chamber are 1/2" and the rear are 9/16". When bench bleeding with the cap off you can surely see the front chamber has a much more powerful stream. Any suggestions are welcome. Thank you, Otto

It worked better than it is now but I never felt that it was 100%. The new master cylinder definately has less volume than the one I took off. Accordinging to O'reilly's auto parts it is the correct part number for the replacement.

With a drum removed and someone stepping on the brake pedal I can see the brake cylinders are operating but with minimal movement. They are probably only pushing out 1/8" each. Any ideas what would cause such little movement or how to fix this. Like I said in earlier post, I successfully bench bled the master and then the whole system with good squirts out of every bleeder with no air. The pedal does not feel firm at all. Thank you

I have bonded linings. Thank you

If in fact I end up replacing the rear shoes, where is a good place to purchase them and what should they cost? Thank you

Merle, I did follow the instructions on how to do a major and minor brake adjustment. I know the shoes are not new and will need replacing in the future but I do feel there is enough material left to do their job. Thank you

How do I determine which rear cylinders are working? I know at least one is working on each side as I can stop each wheel from spinning by hand if someone appies the brake. They just will not completely stop if the truck is jacked up and it is in gear. When I rebuilt the cylinders a year ago I also replaced all the brake hoses. Thank you

Thank you for your service to our country and welcome to the forum. Others on this forum are way more knowledgable than I but if ever I can help out give a shout. Mike

When I obtained the truck a year ago it came with rebuild kits for the cylinders and I rebuilt them at that time but never really watched them in operation. I will do as you suggest and see if each cylinder operates with the drums off and the pedal pressed down. Thank you

Don, thank you for the reply. I did read your link and see that you had somewhat of a similar problem. There is no adjustment in my brake pedal rod. I will re-read your link to look for more helpful info. Thank you

I have no idea of the bore size. I never had the truck lifted to see if the rear brakes were actually working correctly. I was able to go down the road at 60mph and stop with this set up, though when backing out of the garage it did feel like the front brakes were doing all the work. This afternoon I bled the system with the new master cylinder and the rear wheels still will not completely stop when lifted off the ground. At this point I wish I could just go back to a single cylinder master cylinder but I am not sure what one to get because the brake pedal has been changed and the master needs to be mounted on the firewall. Thank you