need brake help on 69 Camaro

[sonic69]

My 69 Camaro started out all drum and manual brakes. First I installed a front disc conversion kit. Same m/c set up and had no problems. I just installed a rear conversion system from ABS power brakes and a chrome m/c and purportioning valve. I can pump the pedal up, but 20 sec. later straight to the floor. No leaks at all and we thought the m/c was bleeding off internally, so we put the stock one back on and same problem. We even tried taking the purportioning valve out and running straight off the master. Still it did the same. With the car off the ground we have enought pedal at the bottom to stop the wheels. One of my friends said I needed a 60's style master cyl. from a corvette to push more volume. I need help with this one. Also I'm keeping it manual and not going power right now. Please someone give me the answers.

[6'9"Witha69]

Residual pressure valves. Mine were needed for the fronts, not the rear. The new MC should be reated for Manual drums all around or power? If it is a power booster you also have an issue with not generating enough pressure.

[sonic69]

It's not power because of the motor not being able to build enough pressure

[68nate]

sounds like there's still air in the calipers. Are the bleeders on the top of each caliper and are they at the upward most point of the caliper? If the calipers only have one bleeder and they are installed on the wrong side (bleeder down) It would cause exactly what you describe due to air getting trapped in the top of the caliper bore. I have seen this happen on more than one occasion.

[sonic69]

All bleeders are up. Can it be Possible it's not pushing enough volume for the pistons?

[68nate]

My 68 has wilwood 4 pistons on all 4 corners using stock drum/drum master cylinder and proportioning valve. Brakes work perfect. It sure sounds like you still have air in the system. What method are you using to bleed the brakes?

[sonic69]

Power bleeder and checking it manually. No air in the lines