OK ... I can not get brake pressure. I have bleed the brakes. When I pump the brakes without the car running pressure seems good but while running the brakes want to go to the floor. I put speed bleeders on a couple years ago and usually they bleed simple and fast.
I have looked over the forum and the internet . One article said master cylinder and another advised differently. Any brake pros here?

thanks,
Gene

You've either got air in the system, or possibly the master is leaking internally. It's also possible that one of your speed bleeders has a stuck open valve/ball, allowing air back into the system when you bleed it.
When you bleed the brakes, use a section of hose on the bleeder(s), and stick the other end of the hose into a container of brake fluid. This will keep any air from re-entering the system.

If you are 100% sure there is no air in the system, then I'd have to say your problem is the master cyl.

From my own experience I had a problem in the '78 I had.  No matter how often the brakes would be bled of air, it would shortly lose its pedal.  It had all the symptoms of a bad master cylinder. 

It turned out to be a bad seal in one caliper.  Instead of leaking fluid it would suck in air and the pedal would disappear.  Once that was diagnosed and fixed, no further problem.

Thanks, for the input. I bought a Master Cylinder.  I have been cussing all afternoon! I don't remember rethreading the steel lines being this difficult, hopefully I get them before my old back gives out.

Wow... I had to cut one of the power booster nuts off and lay the master cylinder sideways and low to get the back brake line on.
    New master cylinder is installed.  Not sure I bench bleed it good enough. When bleeding I got some big bubbles form the R/R the rest only little bubbles.  I have more brake pressure now but still not firm and it does go to the floor. It stops but not too quickly. Brake Light is still on. I guess next step is Pressure Bleed . I will either have to buy one or make one.
Two years ago after some brake work I had a similar problem. The fluid was dirty also. Same as this time. That time all it took was bleeding .  I switched to the synthetic fluid  dot 3, pretty sure I got all the old fluid out.

thanks for the help,
Gene