I have a 64 dodge dart and I recently installed a slant six with a Holley single barrel carb out of a 71 dart. When I first saw the engine it was in the car and running fine even drove 80 down the freeway. My issue is now that its in my car the it will start and idle fine for about 2 or 3 minutes then dies out. So I switched to my stock Carter carb and it starts up right away but wont idle less the 2500rpm. Can anybody give me some advice as to which carb to use and whats wrong with my carbs.

Sounds like a bad vacuum leak with the Carter installation.
Did you use the correct base gasket?
DD

Welcome here. Sounds like neither carburetor is in very good condition, and/or the installation has problems (making sure the base gasket is correct and is the right way round is an excellent suggestion). The '71 carb would have several vacuum hookups not used in the '64 car; did you cap them off? And how did you hook up the '71 carb in the '64, unless the '64 has been converted from its original rod-type throttle linkage to a cable-type setup (in which case the '64 carb wouldn't hook up)?

Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. Tune-up parts and technique suggestions in this thread.

And if you installed a '71 engine in front of a '67 or earlier automatic transmission without installing the needed 1/8" spacer ring between the torque converter nose and the crankshaft counterbore, the transmission's front pump bushing and seal will not last long.

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