Holley Carb Idle Question

[Takt]

I have a 66 mustang with a 302 bored over, with a high rise manifold and dual quads on it. The carbs are Holley 4160 390cfm.

I can't get it to idle below 1,100. It fast idles over 2,200.

I screwed around with it for awhile, unhook all the linkage, reset everything, and the primary idle screws are backed out.

So after all that, I decided it was time to look at some instructions online. Per the instructions, "This adjustment should be made to both the primary and secondary screws in equal amounts.....".

Huh?

Hell, I didn't know it had a secondary screw. Luckily, it gave a picture of the location on the secondary screw.

I've looked all over the damn carb, I don't know where this screw is.

Any suggestions?

Thank you,

 

[thehueypilot]

The screw in your picture is under the sec vacuum diapram. It controls how far your sec throttle plates are open at idle. The sec plates should be almost closed to start with. If your car is running too rich and does not respond to the idle mixture screws you can slowly open the sec plates with this screw to get more air into the carb to lean it out and bring the idle down. It is the alternative to drilling holes in the primary throttle plates. You will have to remove the carb to adjust it unless you have a very small flat tip screw driver and strong fingers.

 

[Takt]

Thank you very much.

I've located the secondary vacuum assembly in the instructions. This will help a ton.

Thank you!

 

[likesoldjunk]

Maybe your problem is a vacum leak. That can cause a fast idle.
check your PCV Valve and hose as well as power brake hose.
Then take some carb cleaner and spray around the base of the carb.
If the engine bogs down, you have a leak and the cleaner is being
sucked in.