MC/Booster combo function - issue?

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.

I would certainly recommend another off the car bench bleed of the master. With what I read it sounds like there are air pockets in the master. Here is a link to our truble shooting guide as well:
http://www.classicperform.com/Instru...brakeguide.pdf

Being that the proportional valve has a internal residual; the use of a vacuum bleeder like you are using will not work as well as you would think. Nothing is going to beat/compare to a traditional proper bench bleed and old fashion pedal bleed.

In the article above we also explain a Syringe method of bleeding the masters that also works well.

Thanks Aaron - I'll do as you suggest tomorrow and report back.

Thanks for the help.
Bench bled again via syringe, then stroked. Bled all lines again via conventional method pumping brakes.
Now have a firm pedal, all is well.
Thanks again Aaron.