Fine Tuning a Holley Carb

[75CherokeeS]

I have a Holley 4160 on my 360 and seem to be having trouble setting the idle. I have it set at about 1100 but would like to drop it a bit more. Turning the idle adjustment screws while the engine is running seem to make no difference. Does anyone know how many full revolutions of the screw from completely closed it would take to set the idle at about 800rpms?

[Lindel]

The idle adjustment screws aren't on the sides of the metering block, are they? If so, then they're idle mix adjustment screws, and you should have them set somewhere between 1 full turn open, and 1.5 turns open.

The actual idle adjustment is almost directly behind and slightly under the throttle (where the cable attaches to the carb). It'll have a flathead type slot in it, with a spring on the threaded portion of the screw.

If you go to Holley's site, www.holley.com (http://www.holley.com) you'll find an adjustment procedure for their more common carburetors.

[ October 09, 2003, 01:28 PM: Message edited by: Lindel ]

[75CherokeeS]

Thanks!

[Obi-Wan]

For the idle mixture screws, 1-1.5 is a good starting point, but you should tune them to your specific engine. The correct procedure is to start with both screws turned out the same distance, then turm them in (clockwise) 1/4 turn at a time, alternating side to side, until you hear a noticeable drop in idle speed/quality. Then back them out 1/8 turn. When you hit this point with one screw, keep turning in the other screw until it drops the idle as well, then turn it back out 1/8 turn.

In order for this to work, the idle speed screw, which is on the throttle linkage and controls how far the throttle arm can return when you let off on the accelerator, must be turned out far enough for the idle to drop.

[75CherokeeS]

Thanks Obi-Wan I am going to put your theory to work this weekend!