Brake grabbing question

[Dodgerdallas]

All drum brakes are new,front to back,all hardware,everything,I had a shop bleed and adjust them and had a bad experience with em and Im not taking it back.The problem is they grab badly,they dont pull to either side so that parts ok but after you apply the pedal over a couple of inches the fronts lock up unless their applied very slowly which is not acceptable in any normal driving situation.My question is by backing the front shoes off a couple notches a solution?Their Pwr brake w a single line Master Cyl

[Dmichels]

Could be a few things First pull all the drums and make sure the primary and secondary shoe is in the correct place and all the springs are correct. Now what I think it is The shoes need to wear in a little This happened to me with new drums. I think this is because the new drum is smaller in dia and closer to the dia of the shoes. The top and bottom of the shoe is contacting first. This cause it to grab. You do not run into this when you are using old drums because the new shoes will contact in the center first befor the top and bottom because of the larger drum dia. Years ago "real" garages use to grind the shoes to the corect dia. Try to brake the edge of the friction material at the top and bottom of the shoe this can help . DO NOT BREATH THE DUST !!!. Drive it around a little the will wear in

[1BAD68]

What about the proportioning valve?
My friends 69 Camaro had that problem and no one could figure it out. They finally swapped that valve and all was good.

[Dodgerdallas]

By proportioninv valve I suppose u mean the junction where u can adjust the flow front to back? I have the old single line Cardone built master cyl and only have the "T" below the MS at the frame. I have the main parts for a front disk setup just don't have the 300.00 to give to autozone to finish it out. Does it matter which way the lines are running in and out of that junction? I may have reversed the front/back lines when all were replaced...

[Dodgerdallas]

As for the drums Dmichels,I said everything was new,the rear drums are new,the fronts are turned...

[Dmichels]

It makes no diference on the T where the lines go there is no proportioning valve on a 4 drum single circuit car. THe front brakes are most likely grabbing because the shoes are not making 100% perfect contact with the drum. Most likely they are contacting at the top and bottom and not so much in the middle.  That is why they use to grind the shoes to the right dia.   Grabbing brakes can also be caused by oil or greese on the friction material.
Dave

[y3chargerrt]

Is the master cylinder push rod correctly adjusted?

[Dodgerdallas]

The MS pushrod was fooled with a litte but was returned to the measured specs from a shop manual-not saying thats not the problem though,are you saying it may be a little too long if its grabbing?