Hi
i just picked up a master cylinder / booster combo for my 67 camaro with front disc, rear drum. It's part no 6474BB2. I've installed it - bench bled the MC, installed and bled the lines. With the engine off, the pedal easily pushes to the floor, about 4" away. I tried bleeding the lines again, but no difference.

any ideas? I thought maybe the booster rod was not extending, but if I take the lid of the master cyl, I can see fluid squirting up when I press the pedal. Could air somehow get trapped in the MC again after the bench bleed? I also checked the proportioning valve, and it is not tripped.

Any help is appreciated.

edit: forgot to mention I bled the lines with a vacuum bleeding tool - in case that's relevant.