i just recently had disk brakes put on my 69 chevelle in the front....i think they were used and came off another chevelle or something relevant but we have bled them over and over and none of my brakes work....we dont think theres any cracks in the line no brake fluid is leaking anywhere other then the bleeder valve when we are bleeding them (duh :X) the pedal gets a bit stiffer not too much while we are bleeding them but once all the valves are closed back up brakes dont work....also when i baught the car 2 years ago the brakes worked

Tell us what parts you changed please. we need more info

Any Chance You Have The Calipers Switched? The Bleeders Must Be At The Top Of The Casting. That Metering Valve Also Is Susceptible To Sucking Air On The Up Stroke. It Is Also Important To Leave The Cap Loose On The Master When You Bleed, As The Suction On The Draw Down Of The Fluid In The Reservoir Can Create A Vacuum In The Reservoir, Pulling Air Back In At The Weakest Seal. Some Of The Mail Order People And Others Sell You A 1" Or Drum Brake Master With These Conversions. Disc Brakes Require A 1.125" Master, And Match The Push Rod Depth Of The Master Hole And The Booster Pushrod. There Are Two Lengths. Last, Make Sure You Power Brake Pedal Rod Is Now In The Lower Pin Hole Of The Brake Pedal.