Well crap. Now that I have the rears working as they should, it looks like i will have to reinstall the residual valve I took out while trying to fix the brake drag problem I had. I was under the impression that the combo valve had residual pressure built in. Oh well, all should be right when I'm done.
Jesus. This got crazy. After reinstalling the residual valves, I still didn't have a good pedal and my rear brakes were getting up to 250 while the front rotors were a cool85 degrees. So, I decided that the master cylinder must be bad and changed it out. Still had the same problem. Today, I replaced the darned combination valve and, after very limited road testing (due to weather), it appears that problem is now solved. The front rotors were now at 150 degrees and the drums were about the same. I will further test it this weekend. My assumption is that the metering valve was messed up somehow since I could get sufficient fluid flow to bleed my brakes. I hate these valves.
So, after messing with this for months, off and on, and thinking I had it fixed. Today, I think I truly do have it fixed. After putting large bore M calipers on the front, I thought that would do it but NOPE, the rears locked up on me in a bend in the road this past weekend. At this point, I decided to examine everything and was planning to check the bore on the wheel cylinders. After I pulled the drums off, I took a look at the brake shoes and then dug out my shop manual for 57 Chevys. In the chapter on brakes, it clearly says the front shoe friction material should be 2 1/2" shorter than the rear shoe. Mine were equal length. I went back to my O'reillys (where I had bought the shoes) and explained my situation to a couple of the gray hairs there. They said, you are right but we can't get the shoes that are short and long any more. Just take a die grinder and cutoff wheel, make a cut and take a chisel and knock that much brake material off. Jesus. I went back, examine the photo again and decided to cut 1" off the top and 1 1/2" off the bottom. Problem solved.....at least I'm pretty sure it is. I locked up the fronts without locking up the rears. in 2 or 3 stops and it took a lot more pedal pressure than it did when the rears were locking up. So, if you're working on drum brakes. Do not assume that the shoes you get from your local parts store are correct. Examine them and compare them to a known correct set or known correct photos. Lesson learned.
I checked a couple. I could have ordered it from Summit but I would have had about 70 bucks in a pair. I decided to try their suggestion and it worked. The friction material is bonded to the steel with some sort of epoxy like glue. After scoring it with the cutoff wheel, I just used a chisel to knock the undesired pieces off. The rest of the material is still bonded like it always was, so it should work.
Replacing the rear wheel cylinders with ones 1/16" smaller bore diameter would probably have solved your problem.
The Jalopy Journal
