The transfer slots are supposed to be slots so that they are available to flow fuel over a slight range of throttle plate opening from the idle discharge openings upward. The top of the slot should be just visible above the throttle plate at curb idle. They probably can be modified, but there would seem to be several easier ways to fix a bog. This larger throttle-blade opening uncovers a large portion of the idle-transfer slot (see photo 9), which draws fuel from the slot at idle. When the throttle is opened more, there is insufficient.

Holley idle transfer slot restrictor

Holley Idle Transfer Slot Tuning

Holley four-barrel carburetors are probably the most common high performance fuel mixing devices on the planet. Given the sheer numbers of carburetors made since the 1950s, you know they work. If there is a fly in the Holley ointment, it’s setting up the idle. Since Holleys are so easy to adjust, it’s also easy to adjust them totally wrong. People will get the idle settings wrong, then blame the carburetor when it doesn’t work properly. That’s a big mistake.

In reality, setting the basic idle on a Holley isn’t difficult. We’ll show you how to do it on both vacuum secondary and double pumper models. What works on this pair of carburetors will work on your high performance Holley, too.

Holley idle transfer slot restrictorTransferHolley Idle Transfer Slots

Holley Idle Transfer Slot Modifications

We’ll take you through the entire process in the slide show below: