72 Blazer break question

[N2Clsx]

Looking for some help here with a problem that I can not figure out. The Blazer does have power brakes. A short time before we parked it for a couple of years a new master cylinder was replaced and from then the brakes were never perfect. We have bleeded (sp?) the brakes atleast 20 times now and not really much better. We replaced the front pads and the rear shoes(that were worn) and nothing. I can pump the brakes once or twice and the work like they should. I can get the rear break to lock up but not the front. What am I missing here?
My next question on a different thread was gonna be the vacuum secondaries will not open on the quadrajet. I have a gauge to check it just got to do it. I could have the line plugged in wrong. Around town it runs great. Could the two be tied together?

Sorry for jumping around on the subjects. These are the last two mechanical problems left on the Blazer. I told Jake that after we fix these I will take him to Azusa canyon or somewhere that he can actually lock in the front hubs and play. Thanks for the help everyone.

[fxdxharley]

first question, did you bench bleed th master befor installing it? may have air trapped in there.
2nd, have you checked your vacuum pressure? you may be loosing vaccum off of idle. check for leaks etc.

[rsavage]

When you bleed the brakes, do you get a strong stream from each bleeder? The reason I ask is that I had a similar problem on a 68 Impala wagon and the problem was a rubber hose going to a caliper that had swelled almost shut from age.

[Ole Beater]

I ended up replacing my front calipers because of uneven braking. It pulled to one side harder. I agree with Rsavage too, the flexibly brake lines on these old trucks can get block. I replaced both with stainless braid from a local supplier.
But it sounds more like air or a blocked hard line to me because the problem is common to both front brakes. Is your warning light on?

[FoxHound]

like harley said if you didn't bench bleed the master cylinder there will be lots of air trapped in it. bench bleeding takes a long time (did for me anyway, about 20 minutes of pumping) but you have to do it until there's no more bubbles in the fluid after each pump.