The adjustment is made using the Idle speed Screw on the side where the Throttle linkage hooks up. Turn the Carb over and slowly back off the Idle screw until the Transfer slot BELOW the Throttle Plate looks like a Square. You do need to be sure the Choke fast Idle screw is off and not holding the Throttle plate open. Set idle speed as low as reasonably possible to avoid entering the off-idle circuit. Off Idle – Just above idle at very light throttle positions, the transfer slot now provides the fuel. Idle feed restrictions and idle air bleeds are used to tune this circuit. 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. I noticed when I rebuilt my Holley that my idle transfer slots were uncovered quite a bit. I have a pretty healthy cam and a single plane intake and I've read my problem is pretty common. I also installed a 5.5 powervalve to replace the 6.5 since my vacuum is around 10-11.

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.

Youtube Holley Idle Transfer Slots Free

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 Modifications

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