Hey guys. I'm running a 650 holley on my 350 and it's been running screamin strong. Today out of nowhere I have a terrible hesitation when the secondaries start to open. High range she runs great. Slow acceleration through the transition is where it's really noticeable. What went wrong? It's going in the shop tomorrow. Where do we start? Power valve maybe? I don't know too much about carbs but some tips would be appreciated on where to check first.
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Mechanical secondaries or vacuum? If mechanical, replace the accelerator pump diaphram and make sure the rubber disk in the float bowl is seated properly. The diaphram could easily develop a small hole over time.

Found the problem. Previous owner installed a pump gas only summit inline fuel filter. The adhesive broke down and a piece was in one of the jets.