4 Wheel Disc Problem

[epeterson]

Hi guys, I have a problem with the brakes on my 1980 Firebird. The car came originally with drums in the back but the guy before me added a disc brake setup off of summit for the rear. Ever since I bought the car I thought the brakes weren't performing as well as they could of been for a 4 wheel disc setup. The pedal feels quite odd (not like air in the lines odd, but hard and doesn't go down the proper length. Only have about 3/4 of what I feel pedal travel should be) Anyways, the first thing I checked was brake fluid, seeing if the levels were right and the fluid color was good, both checked out in the reservoir. My booster is one of those double diaphragm ones, vacuum port is not cracked. I wasn't seeing an obvious problem up there so I took all four wheels of and inspected. It has newer rotors and pads all the way around, but the tears looked a little 'too new'. Kind of like the we're just taken out of the box, put on the car and a brake pad had never contacted them. I thought it could be a bad brake pressure bias so today I set out adjusting the proportioning valve. A few hard stops and half turns later I had gotten the fronts to lockup under very hard braking, but the rear still felt lifeless. I backed off the proportioning valve a little to give me front brakes that wouldn't lock immediately in a panic stop, but that's as far as I got today with the brakes. After getting out of the car and feeling the wheels, the fronts were very hot to the touch (90 degree day and plenty of hard parking lot braking). But when I went to the rear brakes they were cool, as if nothing was happening back there. Do you guys have any suggestions as to what's happening with my brakes? Why would only the fronts be working? Is it a brake booster or master cylinder problem? Thanks for the input
-Erik