I just converted by old brake system to a new setup with discs in front and the larger rear drums sold by master power brakes. Everything went together fine and I bled everything with no problems. The front brakes are fine but the rears don't seem too be getting enough pressure.
There is no air trapped in the line and the master cylinder is brand new. I have the rear shoes adjusted out as far as they will go and still nothing when I push on the pedal. Any suggestions?

Kochese what year, are you using a proportioning valve? Are you getting any fluid to rear when bleeding? How about master cylinder using a disc master?
Gary

My car is a 67. I am using the original metering block attatched to the frame and the small round valve that came factory for cars with disc brakes. The valve attaches to the master cylinder by the lower bolt hole and the front lines run through it. There is a rubber boot on the back of it with a button you can push in for bleeding them. I have a disc brake master cylinder and its new. I'm thinking maybe I have a defective valve because I can't push the button on the back in at all. I didn't even need to push it to bleed the brakes. Any idea what this type of valve does?

Kochese are you using the origanal valve on the frame? If your car came with 4 wheel drum you will need to change that valve. The Ft disc Rr drum porportioning valve slows the fluid to the Ft calipers giving time for the rear drums to catch up. You said you bled all 4 wheels did you get fluis to the rear wheels? Who's Ft discs are you using did you get a KIT?

I beld all 4 corners and got good results. I am using a kit that consists of original chevy disc brake parts for 67 chevelles with the exception of single piston calipers. I have the original round shaped valve that is plumbed into the front lines and then all the lines go into that brass block on the frame. The block on the frame is just a junction point for the lines if I understand it correctly and not a proportioning valve of any sort. The valve is the round one mounted up on the master cylinder. I have a good pedal and the front brakes grab, unfortunately the rears do not. I'm stuck.

Kochese, I suspect your problem stems from the fact your new master cylinder does not have a 10 pound "residual" valve built into the body near the exit port for the rear brake line. If you look at an original chassis service manual for your year, (or 67 to 69) you will see the valve I speak about. It's purpose it to hold 10 pounds pressure in the rear lines to make rear brake shoes work faster. The MP brake site describes it as holding enough pressure to overcome the return spring pressure. In any event, the newer replacement MC's don't have this valve built in because in 1970 or 71, GM went to a "combination valve" bolted to the frame rail. The combo valve did metering (that is the round bullet style valve you now have) and residual functions together. Not sure if MP brakes sells the residual valve separate, but I suggest you remove your metering valve and replace it with the new style combination valve. Apparently GM sells them new still, for about 60 bucks I hear. Your new combination valve will do all function necessary. Check out the freq asked Q's on the MP brake site on valving for more info. If you intend to get your car judged for originality, then you will have to find a disc\drum MC with the residual valve built into it.

This is just a thought here, but Accomb's Razor comes to mind, the simplest solution tends to be the correct one. Did you properly adjust the rear brake shoes?

MP has an aftermarket Residual Pressure Valve. I needed one for my 70 after my disc conversion. Their aftermarket one fit right in. I think it ran around $29.