79 CJ5 brake problem Help Please!!!

Poor pedal...New(not rebuilt) master cylinder. New calipers, pads, front brake hoses, rear wheel cylinders, rear shoes. Both front rotors and rear drums have good thickness. Manual brake system bleeds nicely. First press of pedal goes right to floor, but if you pump it, it comes up to top for a good pedal. Wait a few seconds and press pedal again, right back to the floor.
Feels like air in system, bad pressure, but entire system was thoroughly bled. Bad Proportion valve?

If I plug the outlet port on Master cyl going to the front brakes pedal is great. So I believe prob to be in front. Crimp front brake hoses with vise-grips--great pedal. Anyone out there ever seen or heard of this. Crazy calipers or proportion valve??? Totally stumped and ticked off...

Did you bleed the master cylinder installing it if so check proportion valve

Poor pedal...New(not rebuilt) master cylinder. New calipers, pads, front brake hoses, rear wheel cylinders, rear shoes. Both front rotors and rear drums have good thickness. Manual brake system bleeds nicely. First press of pedal goes right to floor, but if you pump it, it comes up to top for a good pedal. Wait a few seconds and press pedal again, right back to the floor.
Feels like air in system, bad pressure, but entire system was thoroughly bled. Bad Proportion valve?

If I plug the outlet port on Master cyl going to the front brakes pedal is great. So I believe prob to be in front. Crimp front brake hoses with vise-grips--great pedal. Anyone out there ever seen or heard of this. Crazy calipers or proportion valve??? Totally stumped and ticked off...I'd had the same promblem with my 79 cj try the proportioning valve it took 2 before it worked so it must have an ongoing think

Your new front calipers might be holding air. Try tapping them with a hammer while bleeding. Calipers could also be defective, and are retracting the pistons too far into the bores when the pedal is released. They are designed to do this, but only very slightly.
Also, be careful with closing the hoses with vise grips They can be damaged by doing this.