i drove my 85 iroc today to burger king and everything worked just fine, i got there shut it off and came back out about 20 minutes later and for some reason my brakes feel like im stepping on a rock, i can barely press it down, whats causing this

 

My 83 is doing the same thing, my buddy told me it could be master cylinder or distribution block, i guess start with the lesser of the two in cost. I pulled the brake line off on front passenger caliper and had no fluid come out.

 

Have you checked the vacuum line to the brake booster and the booster itself? A leak in either one of those will give you a real hard pedal as well.

I doubt its the master cylinder since that usually gives you a real soft pedal that goes to the floor before you feel the car start to slow down when it goes bad.

Its also possible you have a crushed or blocked line steel line, or a rubber line that has come apart internally and is now blocked.

 

I would check the vacuum line and check valve. You may want to post this in the brake section. May get better responses there.