The AVS series Edeldrock uses a 'quicktune' tunable springloaded air valve to adjust when the secondaries open. But the Q-Jet, Carter and 'original Edelbrock' all use spring loaded air valves, and the air demand of the engine opens them, as they begin to open, they expose a fuel port that enriches the mixture enough till main jet starts to flow. If the secondaries open later they will pull more fuel faster.The more resistance to opening this valve the greater the pull on the main jet, but once the valve is fully open it will have no effect on mixture regardless of spring preload
