Idle Fuel Restriction

Cash App - $AirandFuelGuru

[derekcruz]

You are tuning my blow through turbo carb for me thanks. I have it closer to perfect each time I watch your videos. Thanks for sharing such valuable information, truly pure gold.

[Draiakaiden]

Thanks Randy. My speed demon 750dp has lower ifr's drilled as part of the metering block at .033 from the factory. I am going really lean in the transfer circuit. Your advice has given me more confidence that they need to be drilled out to .035 and tested from there, possibly going even larger.
It's also pretty hard starting when warm, needing foot work to keep it running for the first few seconds. Sounds like this may cure that too allowing it to pull more fuel quicker vs me adding it via the accelerator pump with my foot.

[mikedaugharty]

Awesome video there Randy you do a great job of explaining all the intricacies of the carbs thank you Sir

[MattsRageFitGarage]

Perfect timing on this video. I have one of those 600 CFM summit racing Holley 4010 carbs. It always ran great except I had a lean spot in the transfer slot area of the carb no accelerator pump tuning could ever take care of. During the summer the engine ran rich enough from the extra heat it wasn't really noticeable, but during the winter it was pretty bad at times if I was cruising at slow speeds and stepped on the gas slightly to accelerate more. I enlarged the Idle fuel restrictor jets from the stock .046" to .049" and totally cured the off idle stumble and made a world of difference in how it runs overall.

[Nothingtoseehere]

absolute legend Randy would love to see more vids

[fordcleveland]

Hello Randy thankyou for all these videos and info, also helping me with all my questions when my health is back to normal and the doctor signs me off to get back to working them i sm definitely going to test all these out .

[Bigeu]

With respect to the transfer slot, most literature i've read say .020, so thats exactly where i set my primary throttle blades on my Holley Street Avenger 770 carburetor, and with that, i set the idle at a healthy 800rpm on a ZZ4 crate engine, but i did have to close the secondary throttle plates completely to acheive that. Currently running with the unmodified main body, unmodified front and rear metering blocks and unmodified base throttle plate, IAB(.060), IFR(.033), PVCR(.060), antisyphoning(.028) and emulsion(.028). Its been known the SA line of carburators run leaner because its a street carburetor and not a performance one, but when i compared it to my spare, late 90s 3310-2 carburetor i have, front metering block only, all the orifices are exactly the same size(+/- .01) everwhere, unless its a later revised version of the SA770. If you are familiar, would you care to shed some light on that because i thought the orifices would provide totally different AF mixture ratios due to the design with different models, other than that, so far, so good, all i can do for now is read the plugs(mr43lts), gapped .040, the porcelain stays white with a dark tan ring on the threaded portion, no AFR meter in use yet to properly tune the carb/engine, but thats next on my list. Thanks

[steveduleck]

Good videos! Can you do some on the 0-9776 450 tunnel ram carbs? How to set them up Please

[johnbnos]

The irf should be in the lower facory spot. The idle afr is more consistent under the fuel level. I have fixed more drive ability and idle problems on the newer carbs by moving the ifr down.

[jimoliver]

Can you talk about indexing the needle and seat. Does it make a difference

[claythomas]

Thanks for the YouTubes. I sent something that went to Matthew Cribb. Is that correct?

[aaronblyth]

Hi Randy
Have you done a video on what changing the idle air bleeds do and also how the high speed air bleeds work ?
I have a 650DP on a 351C
The blades were already drilled and I’m just not as happy with it as I think I should be, I’m thinking it might be better without the butterfly’s being drilled.
Had a 750DP without holes and it ran beautifully but it’s much more responsive with the 650.
Would the drilled blades have anything to do with this ??
Best regards from Australia.
Great job on your content 👍🏽👍🏽👍🏽

[DonCatherman]

I have a proform 750.. on a hot 360 SBC...run rich at idle...idle mixture screws are out only 1/2 a turn, any more then that car will stall from being way to rich...I believe I need bigger air bleeds.. am I correct.. transfer slots are about closed...put a bigger cam in it and now it's really rich....at idle....I mean really rich...any suggestions.?...70 front jet..81 back..
Dropped from 74 n 84 helped ..
6.5 power
May drop to 4.5 . maybe drop to 65 front jet n 75 back ..not sure if that's to small or ok....car is 3, 400 lbs, , , runs 11:20 @118 MPH..1/4 Mile..488 gear, , on 31-18.5 x 15 tier....pro street car.78 Grand LeMans.... thanks for any

[TheThirdWheel]

Great video thanks i just drilled some blank IFR air bleeds to to lean out my idle it seems the metering blocks that have the IFR at the top give me a richer idle that i cant lean out . My 4160 came with the lower IFR 65 main jet idle is ok at 13.0 i had a replacement block with the upper IFR 0.30 size and its at 10.0 afr at idle ??? Same jets turned in mixture screws to lean it out not even close 10.80 or so AFR im missing something ? . Jetting down to compensate is not going to work i tried it only think i can think is the carbs that had the upper IFR had a slightly larger Slow idle air bleed ?? I ended up putting the lower IFR block on and the AFR went up to 13.0 ? Can someone explain why this is happening???

[StandAloneAdventures]

Hey Randy, is it possible to use the Quick Fuel 650 dp metering block on a Brawler 600 dp, both are mechanical secondary carbs

[StanfordWelch]

9510 holley 4 barrel smog style carburetor rebuilt..have you worked on it before? The second be be where does it sit..I know the one came out from the fuel sprayer

[barrykilts]

Question, it’s unrelated but what is the best way to refinish an old carb and parts that have no finish or is it needed without sending them to Holley?love your info

[oldsrktracer]

Is there a way I can contact you. I have a Holley HP series 750. Same mods have been done. And I'm idling fat at one turn out . But if I close it more I have that lean stumble. I have to get my gauge pins in there but it's a pretty sizeable restriction. I got this carb from a friend. Low speed cruise it breaks up alot . I assume I'm still pulling from the idle side .

[Darrenlawrence]

Hey randy I’ve tried adjusting mixture screws and restricting the idle fuel restrictor, my wide band still registers 12:8 at idle, ,, curious how you would approach this issue ?

[tonydee]

Hey Randy I wanted to ask you one more thing please & if you can give me your opinion & expertise on this. If I were to do the 750 main body mod to the 850 baseplate but use a 2 corner idle baseplate would I still have to do the modification on all 4 corners of the main body or just on the primary side? Let me know please & thanks. Also keep continuing to bring that knowledge to us we're just loving it man.