Most of the time when I take off in my car from a complete stop, the engine hesitates for a second before taking off. and when I rev it from a stand still it hesitates before reving or completely stalls if I apply too much gas. it does it worse when its cold, but even after its warmed up. Even after a tune-up. Why is this? (72' duster slant 6 225 single barrel carb)

Several possibilities, the first 2 that come to my mind are accelerator pump problem (broken, not adjusted right...) or faulty fuel pump.

A maladjusted or nonfunctioning accelerator pump could indeed cause this kind of hesitation, but not a faulty fuel pump. Take off the air cleaner lid and look down the carburetor (engine off) while you operate the throttle. If you don't get a solid shot of fuel each time you open the throttle, there's a problem with the accelerator pump. Make sure the engine is in proper tune; tune-up parts and technique suggestions are in this thread. Try a base timing setting of 5° or so for a start. Make sure the valves are adjusted correctly; here's the valve adjustment procedure. Make sure the EGR system is either hooked up and working all the way correctly or is disabled fully.

And there's some attention to be paid to the carburetor; see threads
Here
and
Here and here.

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Accelerator pump out of whack strong possibility - fuel pump faulty? Not with these symptoms

BEFORE I would look at the fuel pump things like vacuum leaks, bad timing, valve lash adjustments come to mind.

Follow Dans advice - never fails to help

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Regards,
Fanie Gerber
It's never junk, it's just a part you're not currently using

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