Classic/Antique Car Repair: Brake System, 69 camaro, residual check

Question
I recently replaced the master cylinder and booster on my 69 camaro with a chrome master cylinder.  Since I have replaced it, my brakes have been locking up once they get hot.  (They are fine when they are cold.)  I tried to correct the problem by replacing the proportioning value, two front calipers and two front brake lines.  Unfortunately even after replacing all of the above, I am still having the same problem.  Any advice you can give would be greatly appreciated!  Thank you.

Answer
Alberto, you have fallen into a trap that all of us have fallen for one time or another. Assumed that the newly installed part could not be the problem and start replacing expensive parts hoping to find the problem.There are several possable problems here. First the push rod out of the booster that connects to the brake pedal my not be adjusted correctly keeping some hydraulic pressure in the lines. Secondly the compensating ports in the master cylinder may have become restricted in the chrome plating process and again restricting the flow of fluid back into the master cylinder on brake pedal release. And lastly during the assembly process of the master cylinder they might have installed a residual check valve in the line for the front disc brake. Disc brakes do not use a residual check valve while drum brakes do. This valve holds a slight amount of pressure in the hydraulic lines on release to keep the lips of the wheel cylinder cups in contact with the wheel cylinder bore. Now it is play 007 investigator or conact the folks that sold you the set up and get another one. Good luck.
Brad .