D30 disc brake conversion - Low brake pressure

I just recently installed a D30 on my '67 CJ5 and included a Bronco disc brake conversion. Years ago I made the switch to power brakes with a brake booster and master cylinder from a YJ (1" bore), which has been working fine. I also replaced all of the brake lines at the same time. Now that I'm pushing bigger brakes in the front, my brake action is pathetic. I thought my problem might be with the proportioning valve, so I put in a Wilwood adjustable unit so I could tune the brake pressure. Aside from being able to modulate how much my rear brakes lock up it hasn't really solved the problem. I do have 10" rears that are new as well. The system is well-bled.

At this time I've just about replaced everything and the only thing left to do is scratch my head. Should I consider installing a bigger master cylinder? Would larger front brake lines make a difference? Fairy dust? Appreciate your advice and consideration.

 

Describing your brake action as "pathetic" tells us nothing. Please give more detailed information like low pedal, soft pedal, poor stopping but firm pedal, etc. Then we have something to work with.

 

Soft pedal and poor stopping. Have to put it to the floor to get any action and can't lock anything up. Thanks for catching my omission.

 

Are your rear drums adjusted correctly? Did you bleed the rears? Did you ever get your rear brakes to function after or before the installation of the disks?

 

Rears are bled, adjusted and sporting new shoes/drums. When I adjust the proportioning valve down I can get the rears to lock up as often as a want. Just don't have good 4 wheel braking action (soft pedal).

 

I had the same problem with my 71'. What M/C are you using? I used a Cherokee M/C. I talked to an gentlemen who told me the M/C did not push enough volume to bleed the brakes on the vehicle. He told me to remove the calipers, place a wood block between the pads and raise the caliper as high as possible. Then bleed the brakes normally. Something about air getting trapped and the M/C not being able to push it.
I also had to adjust the rod in the booster. Should only be about 1/16 inch play at the pedal.

 

I'm using a Wrangler M/C. Is the rod adjustable from the cab side of the firewall? I'm not aware of any adjustment on the engine side. Otherwise, your suggestion seems pretty darn easy and cheap...so where's the down side? Thanks for the advice! I'll give it a try.

 

The only ajustement is between the master cylinder and brake booster. For ajustment just turn 1/2 turn at the time and end with 1/4 turn.

 

Exactly, take off the M/C and adjust the rod. I adjusted mine out too far and had constant pressure. I backed it off 2 full turns but need to play with it some more. Going to try out 1 full turn to see it that is right.