Carburetor Idle Adjustment - Summit Racing Quick Flicks

Holley Carburetor not Idling smoothly? Norm walks you through the basics of how to tune your Holley Carb for a smooth idle by completely discussing the idle circuit. From curb idle screw to the idle mixture screws, Norm covers it all. Be sure to watch our other Summit Racing Quick Flicks on Carburetor Tuning: Inlet Circuit Tuning

[SummitRacing]

Hi Ron S,
There are 3 adjustment screws concerning idle on most carburetors. The first is the “Curb Idle screw”. This controls the engine RPM at idle and is located on the drivers side of the carb down at the primary throttle shaft. The other 2 screws are the pair of “Idle Mixture screws”. These are responsible for the amount of fuel that travels into the motor beneath a closed throttle plate (Idle).

[SMPTEflorida]

This is probably the best carb tuning i've ever seen! Nice job!

[SummitRacing]

When adjusting the “Idle Mixture screws” clockwise will shut off idle fuel and counter-clockwise will increase idle fuel. A steady needle on the vacuum gauge is a good indicator that you’ve achieved the correct idle mixture when adjusting both screws the same amount of turns.

[SuperStormyNormy]

Hi Norm, I'm a Norm too, I bought a 502/502 crate motor about 14 years ago and put it in my old Chevy truck, I know I need to educate myself to maintane and tune the motor myself.  It came with a Holley 850 (don't know if it is a double pumper or not).  Subscribed to your channel and will start watching your videos.  For starters I'm sure my carburetor could use a good cleaning, I was told once not to spray carburetor cleaner everywhere as this will dull the finish on my aluminum manifold. 

[Weezulguy]

Sure would be nice to have the camera actually zoomed in on the hardware, might want ro re-shoot this series.

[allenmccluskey]

Hey norm, I wanted to say thank you for all of your videos. They have been of great help to me. I was having trouble tuning my Street Avenger 770 straight out of the box. Thanks to your videos I have been able to get it where I like it. I think Holley should work more on their statements of a carburetor being preset and as simple as bolting right on. It was far from where it needed to be. Thanks to you though, it has exceeded my expectations. Your videos are very thorough and understandable. Thank you so much!!

[SummitRacing]

Maikolo,
Park or neutral will be fine for setting up the idle circuit and or curb idle speed. Ideally when working with your idle circuit you should have a vacuum gauge and a tachometer that will display down to the tens position or better. Keep in mind that the more accurate your tools are the more accurate your settings will be.

[SummitRacing]

Great! Let us know if you have any requests :) Thank you for subscribing!

[SummitRacing]

Stay tuned...they are coming :) We have a total of 8 carburetor tuning videos. Thanks for watching!

[markg.]

Might as well have just listened to this on the radio.

[SummitRacing]

Sorry about that. We will get it better next time :) Thank you for watching!

[SummitRacing]

Hi 001ains,
Because air & fuel distribution is not equal across the intake manifold at idle (closed throttle), it is perfectly fine if all 4 screws are not adjusted equally; but they should be close!

[SummitRacing]

These 2 screws should be adjusted equally as each one delivers idle fuel to 4 cylinders apiece (V8). As suggested in the video, you can adjust using a tachometer, vacuum gauge or the best would be an exhaust gas analyzer. The latter is generally only available at a professional installation shop.
The “Curb Idle screw” when turned clockwise will raise the idle speed (RPM) of the motor, and when turned counter-clockwise will lower the idle RPM of the motor.

[kokonutt]

Thanks alot for the video. I appreciate you putting out this vid for people like me. Now I can tune my chevelle for the first time. Love learning new things like this that helps me do work on my ol school. Thanks again!

[adamf]

I sincerely admire what you guys are doing! I have a suggestion, see if you can show how to hook up a fuel pressure regulator on a carb. car that is using a EFI fuel pump.

[SummitRacing]

A stock or mild build 350 Chevrolet might idle at or around 500 RPM once at operating temperature in park or neutral; keep in mind that ignition timing directly influences you curb idle speed - here I would consider 4, 5 or 6 degrees of initial timing before top dead center. I hope this helps, let me know.

[imken]

Did I miss it? Not a word about idle transfer port sync setup...

[Ticeracing]

So when you count the just shy of two turns then you went to other side and adjusted more vacuum why do you need to remember the first amount of turns it took on the first reading?

[hotrod]

hello have you got any videos tuning blower carburettors with boost ref valves cheers

[travissanford]

I have a 950 quick fuel carb how much gas should I see in every eyeglass because mines way lower than the otherside