69 c20 disc brake help

[treveiger]

Hey guys Ive got a few questions. The PO of my truck put front disk brakes on from a 71-72 chevy c20. The problem is my brakes seem soft and when I push the peddle all the way to the floor itll stop but not fast, and I cant lock them up at all. I checked the brake lines and Im pretty sure its 1/4 for the back brakes and 3/16 for the front. Im going to replace a few hard lines/rubber ones when I get the chance but Im just trying to figure out if theres anything on the truck that you notice that isnt right. Like if my MC isnt right or my Prop. Valve. Im stumped so Im hoping you guys can help me out. O ya before I forget, I changed my pads on my front disks yesterday and when I went to "pump" the brakes to get pressure back on the rotors I got nothing, I messed around with the MC a while and with the rubber on the lid and finally got it to at least make it so I can slowly stop. Ive changed a few brakes out before and never had that happen, I about threw up because I was about to take it for a spin and could of only imagined what would of happened....