A Body Disc Brake Swap 101

spencer0731 said

I converted my 70 340 duster drum brakes to the 74 big brake set up. I also bought a new mastercylinder/power brake booster kit. I had no problem doing the swap but, now, no matter what i do, i can't get any pedal. I can bleed and bleed but, i still have to push the pedal to the floor to even consider stopping. I am not sure if i have the right proportioning valve or not. does anyone have a picture of the 74 disc brake proportioning valve? i have like 4 different types. I can't think of anything else it could be unless i have the brake lines hooked up to the wrong sides of the proportioning valve. can you get a diagram of how to do it right?

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I've seen this on the BBP conversion when the caliper bleed valve is lower than the caliper brake hose. An air bubble forms in the caliper. It appears like the caliper has been bled, but the air in the pocket gets compressed before anything like braking action happens.

One correction is to remove the caliper from the spindle, block the caliper piston fully retracted into the housing (I use a giant C-clamp), then hang the caliper in a way that the bleed valve is higher than the hydraulic fluid hose.

Every time I have seen this, the caliper is mounted to the rear of centerline. It may be corrected by reversing the spindles, but I don't know for certain.