I have a 75 280 w/ AC well there was AC anyways pumps been removed. Does any one know if there is anything vacum related that will stop my heater valve from opening? It was working but the valve itself was sticky so I moved it back and forth at few times with my fingers now NO HEAT. I think lever stripped on the valve but not sure.

The later Z's had dashpot actuated heater valves. (Yes vacuum is needed for the dashpot) This issue has come up before so I'd do a search.

I'd start with making sure the V-line is hooked up. If it is then unplug it and check for vacuum. (car running) If it sucks then that limits you to a , bad controls, bad dashpot, broken/clogged valve, clogged heater core, no water in system ().

Hope this helps

Jim