Set & Tune Holley Carburetor Idle Mixture & Idle Speed

How to establish a baseline idle mixture setting for your Holley carburetor and how to fine tune idle mixture and idle speed for your application.

[rockfordhx]

For people who don’t have a older person or father in their life and has to learn everything on their own I truly appreciate people like this who take their time out of their day to show people like me how to do these types of things purchased a 84 olds cutlass with a 305 in it and holly double pumper 650cfm and learning about the things I own and in case one day I’ll need to tune it learning is always the way thanks man

[bottmar]

This is the most accurate video I've seen. It even shows to turn the mixture screws out an extra 1/2 turn which hardly anyone knows to do. Like he said, it allows a cushion in case of a little contamination in the idle circuit. If you don't adjust that way you will be re-adjusting it at a sooner date. Customers are happier if they don't have to see their mechanic as often.

[junkyardsearcher]

Having trouble today with a brand new carburetor and engine rebuild, tomorrow I am going to go at it with some knowledge! Thank you so very much for this video! I’ve seen others that talk and skim over the other two mixture screws but I wasn’t aware that they were that important.

[daviddntait]

I just subscribed to your channel. I have to say you explained that incredibly clearly! Not too many people know about the secondary idle screw under the carb! Adjusting that screw is key to tuning idle on a choppy low vacuum cam!

[Victor-vcov]

Thank you for the time and effort. Been struggling with my Holley for quite a while. Watched the video and made the adjustments yesterday and problem solved.

[migueljimenez]

Best video on tuning so glad you made this video

[KevinNadeau]

Great video and easy to follow. I'll be following your procedure to adjust my 750 double pumper👍

[TheMrmmkkpro]

Man, I never thought about opening my secondary plates to help out with the idle. I'm running a 1972 455H.O Pontiac with a nasty cam and a 850 holley dbl pumper. My idle adjustment screws are not very helpful at 1200 rpm idle.
Thanks for the idea, heading out to the shop now. Subbed. 👍👍🏁🏁

[roosterable]

All great info, only thing when people hear warm the car they think 10 min idle is good take it for 15 min drive the carb characteristics will be quite different then idling for few miniutes

[dougcoleburn]

Nice info. Amazing how important the transfer slots are yet not talked about. Even in the Holley quick set up manual it states adjust your curb idle screw to suit your best idle.
Mine was way off. I pulled secondaries adjustment screw and put and Allen key screw so I can adjust.

[Brooks]

You're the only video i've came across that talks about having a bigger/racing cam. i was wondering why mine never changed when adjusting i thought something was wrong with my new 950cfm race brawler, now i know & need to take my carb off and adjust the secondary screw on the bottom.
I have to run around 1100/1200 rpm for my cam in my 427 big block.
You gained a sub from me.

[kw]

Another good basic adjustment video...thank you

[flinch]

To underscore why a vacuum gauge is one of the better tools to own, a tale of head service gone wrong...
Decades back, I had an old 350 that needed rebuilding. Guides had gone oval, a couple rockers about to punch through at valve stems, seats were pounded enough to remove any evidence of valve seats ever being cut, etc: ether required for most cold starts and plugs being regularly fouled by oil - a sad victim of unleaded gas and years of service. So heads pulled off, and away to a local machine shop. Cracked and not worth rebuilding, a set of suitable heads then got pulled from a junkyard which received all new hardware: valves, seats, guides, studs, springs/retainers, and rockers. Heads being off, great time for a new cam too so in went a hydraulic flat tappet with 224 duration @ 0.050". Fired up, and while it ran... idle vacuum was between 6 and 7". Power sucked - my engine had easily lost 50hp. Sub 10" vacuum is a horrible number for a modest/middle of the road duration obviously. Tinkered with the carb first of course [not believing new parts and a degreed cam could be so off], and that went nowhere - OFF with the heads, and lap valves to see what the shop had actually delivered: they had dropped valves in without ever doing a valve job - off the charts unforgivingly horrible work [no point in going back to get it "fixed" if that was their attention to detail], and another shop cut the seats.
Trust your vacuum gauge: sometimes a "carburetor problem" is actually something else.

[pauljanssen]

Don't forget to set the float Bowl level first good teaching on secondary adjustment

[phoenixblack]

Many thanks! I have an HP750 on a 355 Chevy small block with a split pattern hydraulic roller cam. The car runs so rich at idle that it burns my eyes and throat if it idles too long.

[ozziea.]

Thank you for the video. I have the 4776-4 Holley. I recently purchased the vehicle. The carb has the 4 holes for the adjusting screws but it only has 2 screws. Did Holley make carbs with 4 holes and only two screws or did my 2 rear ones fall out. The car is running rich and closing both front screws does not shut the car off. Sorry I’m not asking for mechanical advice. I was just wondering if I’m missing two screws. Thank you

[lollipop]

If youre doing the idle mixture screws on a tunnel ram, are you doing the screws on the front of carb one then front of carb two then moving to the rears?.. Or are you doing the front of carb one then the rear of carb one and then the second carb...?

[raymondmenendez]

Hey Mr wolf 🐺--- went through your video again and noticed something that I never heard any one say before. I have an automatic transmission, you say to put the truck in gear to check the vacuum, is that necessary? I always checked with the air filter on and in natural. Thank you for your

[lollipop]

Is there a rule of thumb for how you know the secondary butterflies are opened the right amount? In other words, is it good as long as your idle screws are functional and you have the idle soeed you want?

[FEDERALBOYSENTERTAINMENT]

For some reason when my flap is open all the way when I put in drive are reverse car stalls when I close the flap to about a pencil ✏️ width open it’s fine but bogs when driving Manuel choke can you tell me why thanks