Holley 2280 Power Valves
The Holley 2280 has two (some only have 1) power valves located in the bottom of the float bowl. One is a mechanical and the other is the vacuum. Be sure to keep each power valve assembly together because they work together and are different. Each valve may have a calibration number stamped on the side. Write down the number for each. The vacuum power valve is located on the throttle lever side. Obviously the mechanical power valve is located on the opposite side, or vacuum kick side. The mechanical valve needle is longer than the vacuum power valve.
If you have problem when at part, or full throttle, the power valves can be one suspect. Review the information above.