Main Jets

The 2 main jets in the carburetor are usually different sizes. The larger numbered jet goes on the accelerator pump side of the carburetor.

Power Piston
At idle and low speeds, the power piston is held in by vacuum. as the vehicle speeds up, vacuum drops, which allows the spring loaded piston to move down into the float bowl pushing the power valve open and allowing more fuel to flow.

The only thing that moves the power valve piston is vacuum, so the piston needs to be very free. You can try using carburetor spray cleaner, or as we do Silicon spray lubricant. Spray the piston area as you move the piston up and down, or twist it one way, then the other. Using your finger push down on the spring end, then remove your finger so that the rod snaps up. Doing this repeatedly will make
the assembly pop out of the top. When reinstalling the piston, lightly stake the side so that it stays in the cylinder.

See our Holley 2210 parts catalog.