[Jack21]

When setting the idle on a Holley, if the primary idle transfer slot is open too far resulting in off-idle stumble, and it seems like drilling holes in the primary butterflies is next; try this.

I replaced the secondary butterfly adjustment screw with an allen wrench setscrew. This allowed minute adjustments with the carb on the car, and the engine running. This allowed me to adjust the idle mixture with the primaries (correct slot opening), and the idle speed by opening the secondaries.

I must admit that I became frustrated with this, and in desparation, replaced the Holley with a BG Speed Demon. What an improvement! The engine even sounded better. And my eyes weren't burning anymore. I'll never put another Holley on a Hi Po engine again.