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There are several things it could be. To keep from hiding the symptom and not fixing the problem, check things in a certain order.
1. make sure ignition is advancing properly
2. make sure carb is clean, no blocked passages
3. jetting, your's sounds fat enough
4. power valve needs to open at the needed vacuum
5. accelerator pump needs to supply enough fuel till the boosters come on line

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it won't get any better until you get some gear. Putting a 2.73 in a 440 car is like having a pretty girl friend that has bad breath. yeah you can get past it but it will take a second or 3.

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There are several things it could be. To keep from hiding the symptom and not fixing the problem, check things in a certain order.
1. make sure ignition is advancing properly
2. make sure carb is clean, no blocked passages
3. jetting, your's sounds fat enough
4. power valve needs to open at the needed vacuum
5. accelerator pump needs to supply enough fuel till the boosters come on line

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1. I'm chasing down a part throttle ping so I've been working with the advance quite a bit: it works.
2. It is a relatively new carb. I can't say for sure I don't think it is funked up.
3. I agree. Could possibly go back to 72s on the primary even.
4. My idle vacuum is 12inhg. So I'm running close with the 6.5 PV that comes in the carb from what I understand.
5. I'll check the pump shot out on Tuesday this coming week when I've got a bit of time free during daylight.

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"The off-the-line hit is great.

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Holley's FAQ says this:

"QUESTION I have a vacuum secondary carburetor that bogs when the secondaries come in. What will cause this?
ANSWER Bogging and hesitation are caused by the secondaries coming in too quickly. You can install a heavier secondary spring and this will prevent the secondary from coming in too soon. If the engine is sluggish in response at full throttle then the secondaries may not be opening soon enough. You will then need to go to a lighter spring. The spring kit is part number 20-13 which will have 7 different springs to fine tune with."

Is this possibly what I'm chasing?

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Start with the obvious and easy fix, then work from there. Pump shots and cam changes will tailor the enitial and mid throttle tip in, but if its coughing when you nail it all at once to the floor, the most likely problem is that you're secondary's are opening too fast.

Put the strongest spring possible in the vacuum canister and see if the problem goes away. If it does, then we know we're on to the right issue. From there, start weakening the spring, I'd go (2) springs at a time, until the problem starts to show itself again. Back off to the last spring that didn't bog..... done. From here, you can start to mess with pump shots and cams, and nozzle sizes. Being off on those shouldn't cause a complete cough, though. Those are things that will add throttle response if tuned properly, but it sounds to mee like the secondary spring is your issue. Especially if those other items are at stock spec. for an 80508.

It seems to me that a good running 440 really should be able to take all of 750cfm right away, I had the same carb on my old 383 with the lightest spring available in the vacuum can, and it would take a tromp to the floor without hesitation. But, your gearing being so far out of line with the rest of your combo is likely to blame. Going to a set of 3.55's would make a world of difference, and still allow 60 MPH fairly comfortably. I'd look to change the gearing ASAP.