So I have pluged the outlets in the master cyl and it has a firm pedal. I then left the plug in the front line and hooked up the rear brake line and had a firm pedal. As soon as I hooked up the front line I had no pedal. I then clamped off the rubber brake line at each front caliper. I had a firm pedal but when I unclamp no pedal. I have replaced the calipers 2 times and vac bled and foot pump bled and still no pedal. This is a 78 camaro sub frame with 78 brakes. Chevy changed calipers around 80 to what they call a slow drag cal. This cal will not work with a reg master cyl. Anybody know how to check on what cal this could be. I am running out options?