my dad recently bought a 72 ss 402. it is completely stock for right now. my question is when the back secondaries open up the car just seems to bog bad. is this because it is running to rich. i dont know a lot about carbs, i am more on a fuel injection guy. any help would be great.

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stock 72 ss waiting for mods

Holley or q-jet?
It can be either a lean or rich stumble. It could be a problem with the accelerator pump, or a timing issue. If it still has points, it could be that the points are worn and the dwell and timing are off. Give us a little more background, and be sure the basic tune-up items are in good condition. Make sure the points (if equipped) are in good condition and the dwell is properly set. Make sure the timing is where it's supposed to be, and set the idle mixture. If the problem persists, then we can get into fine tuning the carb.