Understanding Your Holley Idle Circuit

[@mikef-gi2dg]

Wow, you are truly a BAD A CARB MAN. I took my 1850-3, the only Holley carb model I have ever used over 30 years, and drew on it like you did, and the relationship of idle and transfer just leaped out at me. Now I understand why things i tried many, many, years ago didn't work, on a very mild SBC. The way you broke that down with a marker was huge. More Holley 101, with a marker videos would do the trick for us old timers who lose our way on Holly's from time to time, from a BAD A CARB MAN!

[@holleycarbshowtosadvice40y90]

Thanks bud

[@pelicansurfking]

Halfway through this video and I understand exactly why my truck idles with the needles all the way in. Like you say, "Too much fuel flow through the actual transfer slot!" Thanks much. I think I'll just watch them all.

[@holleycarbshowtosadvice40y90]

I'm glad i could help. Thanks

[@Adrenacyde]

Randy, just found your Channel. I know my way around a 4150 pretty good, but you've definitely made me view a few circuits in a different light. I do feel like a Novice could easily gain confidence with these productions. The best part of these videos is that you thoroughly explain AND demonstrate the path, theory or method several times over so it really sticks in your mind. Having all of the pieces on the bench (float bowl/metering block/main body/etc) really helps the viewer as you follow along. The camera also gets in nice and close and clear. A newly earned Sub from Canada. Thank you.

[@holleycarbshowtosadvice40y90]

Thanks for the kind words.

[@umakemerandy3669]

Hj Randy. Randy here. Idle air bypass, cool! Never saw that before. I got a qft 750 ct carb that came on my camaro and I bet that will help me fine tune. Love that. I havent seen anyone else mention that.

[@holleycarbshowtosadvice40y90]

Happy to help. Take care

[@denistorres8337]

Thank you for the great explanation and sharing your experience.

[@holleycarbshowtosadvice40y90]

You are most welcome.

[@26tbucket]

Thus is the only explanation that has ever made sense. I now know that I adjusted idle too high and the teanfer slot is dumping fuel. May need to drill the holes. Hope u have a video on that

[@holleycarbshowtosadvice40y90]

I do have a video, i believe its under idle circuits mods for high duration camshafts, but you might try raising the secondary idle speed and lowering the primary side, sometimes this works if not then drill bypass holes. Hope this helps.

[@paulhershberger8774]

Thanks!

[@holleycarbshowtosadvice40y90]

Thank you

[@PeggyParrow]

What does the holley book cover look like, i want one , There are so many books out there!

[@holleycarbshowtosadvice40y90]

The holley book i have just mainly deals with specs and parts. I'll get that information for you in the next couple days.

[@holleycarbshowtosadvice40y90]

My book is the ( Holley Performance Products 2012 ) there may be an updated version now. My copy is falling apart lol. Hope this helps.

[@davecaresforyou7606]

You are brilliant

[@holleycarbshowtosadvice40y90]

Thank you

[@e3skeen427]

Lots of good info, thanks

[@holleycarbshowtosadvice40y90]

Thanks for watching

[@StandAloneAdventures]

Are the idle air circuits strictly for idle during operation? I’m new to tuning carburetors and your channel has helped me a great deal in understanding the tuning of the Holley carburetors. Thanks for the videos you post because it is a blessing for people like myself who truly need this type of help.

[@holleycarbshowtosadvice40y90]

The idle air bleeds are for the idle circuit and for the transfer slots. The transfer slots feed fuel to the engine between idle and where your main jets start flowing. Hope this helps. Let me know if you have any questions.

[@jacobrusso9522]

Hi. Thank you for a great understanding of the idle circuit. I just bought a summit 750cfm carb for my pontiac 421ci. The engine is very tame/lame. I can not get rid of my off idle stumble no matter what I do to the accelerator pump settings or idle mixture screws. If I'm barely cruising or at a stop and barely touch the peddle, it stumbles. I'm about to send it back but thought I'd ask your opinion.

[@holleycarbshowtosadvice40y90]

Alright do you have m08750vs or a traditional 750 holley, tell me what you've tryed so far any information will help.

[@huntzilla360cave3]

My father and I are trying to get our logging truck running, we can get it to run if we drip some fuel in when we turn it over, then if we hold the throttle it'll stay alive for a little while but slowly get rougher. I adjusted the floats so that they barely trickle out of the port, and I went 1.5 turns out from bottom on both idle adjusters.. we checked all the spark plugs and cables, we got the distributor spot on, with harmonics line and the jagged timing plate and adjusted while we had it at a stable higher RPM.

[@holleycarbshowtosadvice40y90]

I need to know how long the truck has been setting up, and smell the gas does it smell like shellac ( stinks) . Also I need more information the year of truck, and the engine cubic inch. You could have bad gas if it set up very long or could just need the carburetor overhauled. With a little more information I'll tell you more things to check.hope this helps.

[@huntzilla360cave3]

@@holleycarbshowtosadvice40y90 so this is a refurbished 600 CFM Holly, it is on a 4-barrel intake manifold for a Chevy 350 84 Blazer, it was running, earlier this year, we emptied out the fuel tank and the lines and put fresh fuel in, there was fuel pouring through when we pressed on the throttle, there is 0 idle because even when we said it fuel with the throttle it was able to run, able to run without using throttle and dripping in fuel, but I believe it may be timing issue then, because we put a two barrel 500 or less CFM and when we use throttle it ran but once again as soon as you try to let it idle by itself there's no hesitation between zero throttle and it dies off, so we are taking the distributor from one of our other trucks currently and putting it into this one. The distributor that we are taking out is from another K5 dump body, truck runs perfectly fine all eight cylinders and shoes on the gas. We put in a brand new distributor in that one, because that is our plow truck, we're taking a working distributor and throwing it into the skidder that's the next step so far. Because if that isn't it it skipped a gear from the timing chain and that worries us

[@holleycarbshowtosadvice40y90]

Well good luck.

[@holleycarbshowtosadvice40y90]

If you think that your engine has jumped cam timing, the best way is to line up #1cylinder on compression stroke at maybe 8 degrees btdc and remove dist. Cap and check to see if the rotor button is pointing towards #1 dist cap plug wire, but its to late after you move the distributor timing, now use this for future reference. Now if its jumped cam timing the compression will be low on all cylinders if its off one tooth usually on a stock engine it'll be about 90 psi enough it will run but poorly and will be real low on power, advancing ignition timing will help but the engine will still be low on power. Another way is to remove the distributor cap and turn the crankshaft with a wrench back and forth and watch to see how much movement of the crankshaft before the distributor rotor moves, this measures timing chain slop, if there is alot of movement before the rotor button reacts this is another sign that timing chain and gears need to be replaced. There is still another way but this should tell you if its jumped. Ok good luck. Hope this helps.

[@huntzilla360cave3]

@@holleycarbshowtosadvice40y90 thank you, definitely will check this out because we haven't been able to get to the machine yet, but the cap was in the same spot that it was started in. So we'll check that but I'm pretty sure that the arm was pointing at cylinder one contact. I'm going to post a video showing a held throttle and it is still dying out.

[@Itsyaboyharry98]

Trying to get a 650 to run on my 13b Rx7. This explanation of the transfer slots makes much more sense than Holley's

[@holleycarbshowtosadvice40y90]

Thanks and good luck.

[@donthompson2188]

Don’t know if you’ve mentioned this before but I noticed the body has been machined flat. One of the main reasons these carbs don’t work correctly is the main body warpage and the passages bleeding across one another.

[@holleycarbshowtosadvice40y90]

The main bodies do warp ,especially since they came out with the nylon bowl screw washers that everybody over tightens. Take care.

[@alldabeanzracing9650]

good video!

[@holleycarbshowtosadvice40y90]

Thanks

[@theredwedge9446]

Randy, on your other channel that was hacked years ago, you made a great video on modifying the throttle blades for high duration cams by drilling holes in the plates. Can you please advise if cracking open the secondaries is a good alternative to drilling holes? Pros and cons? There is not much info on secondary idle to add air to help close the primaries. Running a 750 AED Holley HP double pumper with a big cam on a small block that’s rich at idle with a bit too much transition. Plenty of timing at idle. Also, can you please confirm the maximum the T slot should be exposed? I keep reading .020-.030, but you mentioned up to .060 is ok. Thanks

[@holleycarbshowtosadvice40y90]

The transfer slots can vary on a all out drag car, if your looking to clean your idle up then I would stay around .035 for the transfer slots and about .035 for the idle fuel restrictor this is the average ,as far as how much air to bypass, you can open the secondaries , but on a real radical cam it might not be enough you don't wont to pull any fuel out of the secondary transfer slots I still like to drill my throttle plates and then use the secondaries to finish the tune, all these numbers change with the size carb and cubic inch of the engine.and how radical the engine is. Some of the newer holleys have an adjustable bypass built in. Hope this helps.

[@StandAloneAdventures]

Hi Randy, I have a rich idle and was wondering if drilling these holes would help correct my issue. The carburetor is set up pretty good I believe according to my afr gauge, it shows a 13.5/14.1 at cruise and pretty dang close to the same when accelerating hard at wot, but at idle and idle only it’s showing a 11.2/11.6 and I’m stumped on this one. My 4 corner idle screws are along with air bleeds and power valve are just where I need them to be and the carburetor works amazing, no stumbles or nothing, I just can’t seem to get it to idle any leaner. Carb is a 600 Brawler with mechanical secondaries and electric choke and it works great on my 306 sbf. Any advice would be greatly appreciated and thanks again for all the schooling you have provided for me with your videos because without them the carburetor wouldn’t be working as well as it does. You have been by far the best carburetor tech I’ve ever had!!

[@holleycarbshowtosadvice40y90]

If you have a 4 corner idle circuit you might not need to drill holes in the butterflies, try changing your idle air bleeds larger in increments of .003 thousandths, change all four bleeds and reset your idle mixture , if that's not enough go .003 larger and reset mixture each time this should take care of your problem. Hope this helps.

[@UpVoltageOverclocking]

can you do a video on proper setup of electric choke... i have a 600 cfm 1850 vacuum secondary that had a heat riser pipe for the choke coil, i removed that coil and put an electric coil on it, do i need to change the housing that screws to the body of the carb? what do i do with that passage that draws air in? do i plug it? do i leave it open? ive heard plugging it overheats the coil. please i would love information on this. i have seen the holley kits and the housings look like they have some small filter on it and say no to block the fresh air intake, but it looks like they have a metered air jet where the passage connects to the carb body. thanks

[@holleycarbshowtosadvice40y90]

Do not block your vacuum to your choke housing, I'll do a video.

[@JustTruckinAroundLLC.]

I have a Holley 4118-2761 that is giving me absolute fits. I am having trouble finding factory specs and really any informarion on it. Where, if at all would ya'll suggest I look? Thanks again for the great content.

[@holleycarbshowtosadvice40y90]

I have some specs primary jet 68 and secondary jet 78 , accelerator pump squirter .025 power valve 85 , vacuum secondary spring color yellow. Hope this helps if not let me know if I can help.

[@dannysanchez5301]

Are you going to finish the series on converting a 2 corner idle to 4 corner idle?

[@holleycarbshowtosadvice40y90]

Absolutely

[@holleycarbshowtosadvice40y90]

There's three parts to this mod, part 2 an 3 are further down.

[@emmetthelm4160]

In the video, you mention that if the mixture screws are all in, and still idle, then fuel is running in through the transfer slot. I have a pair of 509cu big cam marine engines that are fresh, on the dyno they ran flawlessly, but once in the boat and idled down to shift into gear I had to adjust the idle and mix to about 850 R's idle and about 650-700 R's in gear. I am considering the throttle plate mod. My carbs do not have secondary mixture screws.. They are 800/Mech Secondaries. Should the secondary butterfly's be drilled also or only the primary to stabilize the idle?

[@holleycarbshowtosadvice40y90]

Emmett don't know much about boats but make sure you timing is right before you do to much to your carb, I drag raced alot, had a 1050 three circuit dominator on a bbc an had a stumble, I locked out my timing on my msd distributor at 36 degrees the engine ran so good, the stumble was gone and the idle was perfect and ran at 200 rpms lower at idle. You engine might have all of this and i don't know about locking your distributor out in a boat, may want to talk to a boat racer, but as far as drilling the holes in the butterflies its ok to drill the secondaries if you need the extra air or if you rather drill 4 small holes compared to two larger holes it will work either way, you just won't to bypass enough air to close up your transfer slots to about .020 to .030 thousandths and if you have changeable idle air bleeds try opening them up a little see if it helps. Hope this helps.

[@randywl8925]

Honestly, I like the way you repeat and keep going over in different ways how these passages work. You could go over it once and say it goes from here to here to there and call it good. Some people catch things and understand it first time around. The way you showed the passageway to describe what they do was extremely helpful with a little bit of repetition and wording at differently each time. I love the way you do your videos. You make what to some is rocket science, understandable into laymen's terms. I've never understood before today, how that little air bleed functions. Great stuff. 👍 Just out of curiosity, what behaviors might occur if that bleed was not flowing correctly.... slightly plugged up? I have a friend with a 70 1/2 Z28. It has a 350 with a 780 vac secondary. It idles best with the idle air screws 1/4 turn open...... .....something is leaking inside, I'm sure.

[@holleycarbshowtosadvice40y90]

There are several things can cause this concern one is the transfer slots to far open or idle air bleeds restricted or a power valve slightly leaking this is what I would check first . With the carburetor removed look at the transfer slots and see how much is exposed .035 is good. Hope this helps. Thanks Randy

[@randywl8925]

@@holleycarbshowtosadvice40y90 Thank you for the reply. This factory carburetor has direct manifold vacuum. The primary throttle adjustment screw is virtually closed. I assisted a couple years ago to get this carburetor running. It has the wrong gaskets throttle plate screws in the wrong position causing incredible flooding and the accelerator pump needle was seized in place. Although it's not recommended by Holly to touch them I did change the secondary stop screw. I recall closing the throttle blades then turning the adjustment screw one quarter turn open. Anyway it currently runs and drives okay but the exhaust smell burns your eyes even though there are no plumes of black smoke. So in a nutshell, it runs and drives okay but the idle air screws are 1/4 to 1/2 turn open and the primary throttle blades are nearly shut. I believe the initial timing is set at 12° At some point when we remove the carburetor, I want to do it after we have the engine idling as well as it can be. At that point when removing the carburetor I'll know exactly what the transfer slot looks like. I will also be able to check how far open the secondary adjustment screw is. When figuring out the problems that the carburetor had a couple years ago, the one thing I didn't know to check was warpage on any of the surfaces. This time will check for that in addition to installing different power valves.

[@ford351cleveland]

Thankyou for the video you guys deserve way more subs keep.up the good work 👏 . May i ask does fuel pressure effect idle quality and very very light in gear acceleration ? Any advice

[@holleycarbshowtosadvice40y90]

If fuel pressure is correct and carb is not flooding no it will not effect idle quality or cause off idle hesitation, let me know if I can help you with any problems. I'm glad you enjoy the videos.

[@ford351cleveland]

@@holleycarbshowtosadvice40y90 Hello thankyou for your help. My problem is that i have very lean idle when motor is a bir cold and also lean of idle accelration i have pulsing 3 psi fuel pressure and nswaped a 25 squirter to a 35 it improved a bit but not ideal. I would really like to idle as low as i can liek 550 rpm etc and wondering how i acan achive that with the help of aome carb tuning. I am vacuum leak testing my engine this week as i only have 7 inch od vacuum at idle and not the big of a cam and also have 175 psi cracking compression so trying to find more vacuum and hope to be the carb

[@holleycarbshowtosadvice40y90]

I dont believe your engine is ever going to idle down properly to 550 rpms with even a mild camshaft there is just not enough vacuum , and that's why it's so lean.If you are determined to due this ,you might try talking to a camshaft company and try a special cam and possibly work with your ignition timing. Good luck .

[@ford351cleveland]

@@holleycarbshowtosadvice40y90 thankyou for the reply good sir much appreciated. I have re watched your videos again on the fuel economy series and i an going to try to lean out the transition circut on my 1850 since while crusing at 2400Rpm 65mph my afr is reading 13,5. Will it be better if i change the booster to an annular one for better signal as when under ver light accelration its goes lean up until 18 afr and i changed the squiter from a 25 to 35,might it be weak signal on the carb ? Thankyou

[@frankrizzo3922]

😁 Alrighty appreciate your help however I do have a weird situation with a brand new holley 650 dp - it is a 4 corner idle carburetor and no air horn from factory... only a week old now... - anyway its on a new 302 Ford with bit of cam and heads but I'm getting alot of popping in the exhaust while engine is cold it clears up once warms up.. I've tried adjusting air/fuel screws which is effecting engine rpms but the popping continues till it warms up... Good throttle response when warmed up but I know this isn't normal popping so much when its cold.. if I fatten up the ratio ( 2 turns out) black smoke is present during idle... so it's either to lean or to rich... can't seem to adjust it to a good happy medium... I've got ignition timing about right.. weird for such a new carburetor all stock out of the box.. I thought you'd be a good one to ask this question 🤔 Thanks in advance for any help!!

[@SHONTONGA06]

Randy, on an older double pumper, with only 1 metering block with idle mixture screws, can't you open the secondary's slightly more if you need a little extra idle rpm while keeping the primary closed enough to keep the transfer slot exposed just enough? That way you don't have to drill the throttle plates..

[@holleycarbshowtosadvice40y90]

Yes you can Nick to a certain degree and there is nothing wrong with doing it that way, I'm just use to drilling holes in the plates to bypass the air. I guess it comes down to personal preference. Have a great day.

[@SHONTONGA06]

@@holleycarbshowtosadvice40y90 I can certainly see that having a better effect on a 4 corner idle circuit carb, I was just curious if doing it with my 650 would work.. I don’t know what motors I’ll end up possibly using it on, is why I hesitate to drill it lol thank you sir!

[@holleycarbshowtosadvice40y90]

I totally understand , keep working on those carburetors and have a great day.

[@tj484]

Hay I have a 3310 750.i rebuilt it.but when u give it gas on the Dench gas pools alot out of the bottom plate where there's a small check ball .and not comming out of the top nozzel.?

[@holleycarbshowtosadvice40y90]

I think you have the wrong metering block gasket, the wrong gasket between the metering block and main body will cause this problem, match your gasket.

[@beyondupnorth]

I have a 650dp that wont flow enough fuel on the idle circuit 280 comp cam, 351c 4bbl, torker intake with common plenum for all ciylinders. So to enrichen the idle circuits is it better to add 4 corner idle circuits or open the main well orifices? Also with a open plenum manifold is it necessary to jb weld the channel from front to rear in the throttle plate base for 4 corner idle circuits? Thanks

[@holleycarbshowtosadvice40y90]

Make sure you don't have a vacuum leak anywhere if not check the idle circuit for restriction or blockage, now if the carb has been rebuilt look at your throttle plate gasket it is so easy to put the wrong gasket on and it will block your idle circuit, remove your throttle plate from your main body and lay your gasket on your main body if it covers any of the mixture holes (the two outer holes on the main body) this will cause it not to idle. Try this first and let me know.hope this helps.

[@beyondupnorth]

@@holleycarbshowtosadvice40y90 it runs not too bad, but has always seemed just a bit lean and it liked a little squirt from the Aceell pump. Especially when not fully warmed up. Carb was new and behaved this way back 25 years ago. Just digging it out of mothballs and needs a clean and rebuild now. Haven't attempted to fire it yet. Drained tank and fresh fuel. My idle screw is set to high and I need to enlarge the .045 holes I drilled ( years ago) in the primary butterfly as 3/4 the transfer slot in exposed. From memory the base has never been off the carb. It has run 13.27 @ 104 in a 3400 LB all there street car so no real complaints except occasionally needing to tap the throttle to give it a little accelerator pump shot while driving on the streets. It needs float needles, power valve ( leaking) metering plate and bowl gaskets and a good cleaning. I'll follow the points in your videos and check that base gasket before considering any further mods.

[@holleycarbshowtosadvice40y90]

Please let me know if I can help, usually if it has the wrong throttle plate gasket it want idle at all. There all a little cold natured but should be fine as it warms up. Let me know I'll help if you run in to any problems. Hope this helps.

[@beyondupnorth]

After more digging the biggest issue was my front and back inner air bleeds were plugged and I never had anything small enough to go through them . Some furnace drills and a pin vice and this car has never idled this good. Starts warm without touching the throttle now. I'll have to look into some upgrades for the 30 year old 650dp but just glad to have it running decent for now.​@@holleycarbshowtosadvice40y90

[@alicenfred]

My 650 Holley double pumper does not have an idle set screw on the primary only the secondary?

[@holleycarbshowtosadvice40y90]

I've never seen a 650 dp without a primary idle adjustment screw, without an idle screw of some sort the throttle blades would bind up and there would be know way of setting your transfer slots. I think its miss built or the screw is just missing. Good luck.

[@nickwilson2475]

So... Would I need to drill holes in the primary throttle plates if the idle adjustment screws are only out 1/2 turn on all 4 and I still have a rich idle? I have tried cracking the secondaries more but then I'm closing down the transfer slots more that recommended. Carb is a 570 vacuum secondary on a 302 with trick flow stage 1 cam

[@holleycarbshowtosadvice40y90]

Nick if your transfer slots are right, you can try a bigger idle air bleed , if you have screw in bleeds. Other than that yes you have to close up the transfer slots more and drill the butterflies to bypass more air. It is possible on some carbs to convert to screw in air bleeds if you have enough metal around the press in air bleed.hope this helps.

[@nickwilson2475]

@@holleycarbshowtosadvice40y90 Ok thanks, I've been trying to avoid drilling holes. I think I'm going to start small maybe a 1/16" and go from there.

[@dougcoleburn1579]

so on a holley 600 vacuum secondries is it a problem if the curb idle screw is turned out so much that the transition slots are no longer showing? Thanks

[@holleycarbshowtosadvice40y90]

Not always, if you dont have a lean spot coming off idle ,chances are you wont have to do anything. Sometimes when you close your throttle plates that far you can cause the throttle plates to stick or bind in the bore, always remember almost every combination is different. The good part about this is most all of your idle mixture now is controled by the mixture screws. A race motor usually you have to modify it to close up the throttle plates that far. Hope this helps. Ps the more you get into this, the more you'll understand, you have to strive to get what i call a great tune. First acohol carb i built when we where racing open wheel modifieds took some time to get just right but the throttle response sounded like thunder cracking when i hit that sweet spot, so quick. Sorry sometimes i get a little long winded. Take care.

[@TedRitchie-cz5pu]

so I did everything as it’s supposed to be , can’t find any vacuum leaks , blocked off anything that might leak, all proper gaskets and still too lean to idle. apparently it use to idle. there is one semi blocked circuit on one side of the secondary block that i can’t get any better. it’s a 750 vacuum secondary. any ideas? the carb kit came with flat faced float needles , are they ok? the 45 the time i took the carb apart the back bowl was empty (first time that happened) but its ok now

[@holleycarbshowtosadvice40y90]

Ted are you near jacksonville florida?

[@TedRitchie-cz5pu]

thanks for responding, i’m in Canada. i changed both metering blocks and all good now. what’s weird is i checked every passage and they were all clear.

[@holleycarbshowtosadvice40y90]

Somewhere along the line it must of had a restriction in the idle circuit, its always good to have extra parts. Take care.

[@jeffrevill6492]

How will I know if I drill my hole too big?

[@holleycarbshowtosadvice40y90]

The engine won't idle down low enough if the holes are to big. When I drill holes in the butterflies I'm creating a vacuum leak to raise the idle so I can close the butterflies to keep the transfer slots correct. Hope this helps.

[@auxc.6805]

So if my car is idling rough on cold start and blowing white smoke that smells a lot like fuel. The culprit is these circuits not being cleaned out and are just clocked up.

[@holleycarbshowtosadvice40y90]

I need your carb information and all your information about the concern. If it only happens during cold starts it may be your choke is to rich.

[@auxc.6805]

@ from you reminding me about the choke that i totally forgot, i was able to properly reset and adjust the choke. Huge thanks for the reminder cause after doing it, no more white smoke and engine idles super smooth off coldstart and fires up perfectly fine now. Also i have a holley carb 4 pumper just like in this video. Super helpful advice. Anyone who says otherwise is probably dumb.

[@holleycarbshowtosadvice40y90]

Thanks bud

[@proracing9025]

My holley sat all summer, won't idle ,I need to keep pumping gas to keep running, then kills .

[@holleycarbshowtosadvice40y90]

I would clean the idle circuit or maybe just go ahead and rebuild it if its been awhile. Hope this helps.

[@proracing9025]

@@holleycarbshowtosadvice40y90 it's only year old , will take it apart and clean it out

[@eddieb1408]

I have a 830 main body on a 850 base plate, do I have to modify anything for it to work?

[@holleycarbshowtosadvice40y90]

If your trying to increase the velocity in your carb the 830 main body want help you, because it has the same size venturi as the 850 so if you modify the 830 main body and you will still have a 850, if you are trying to increase velocity use an 800 or a 750. Back to your question yes the 830 has to be modified to match the 850 idle circuit and matched to the 850 plate. Hope this helps.

[@eddieb1408]

@@holleycarbshowtosadvice40y90 I thought the 830 was a 850 main body, by putting the 830 body on a 850 plate, they wouldnt need any modification. Thanks for your help

[@coreykallmbah7580]

I have a old 4779 and I’m tuning the idle using a wide band . I have to have the idle screw out 2.5 turns to get 14.1 afr at idle . If I turn it in to 1.5 it goes dead lean up around 18. I’m thinking I need a smaller low speed idle bleeds

[@holleycarbshowtosadvice40y90]

Corey have you done any mods on the idle circuit, air bleeds , idle fuel restrictor , transfer slots and when did this concern start also have you checked for vacuum leaks. And are your air bleeds changable. Let me know and I'll try help.

[@coreykallmbah7580]

It was a 750 that I ran on a 408 the only mods it has is a pro form center section but it’s un touched with screw in air bleeds . I did change the power valve in it because I run a big cam and only have about 10 “ of vacuum . Transfer slot is about .035 carb has great throttle response and even good part throttle and full throttle afr it just takes 2.5 turn out on the idle air screws to get it ideling in the 14.1 range . If I go less it goes very lean 1.5 out puts me in the 18.1 range . Idle is 850 rpm and timing is 30deg locked out .this is a 6.0 ls based engine . Thanks for the advice ,it’s much appreciated

[@holleycarbshowtosadvice40y90]

check and see if you have an idle fuel restrictor if so what size, I would run .035 and if this doesn't help then try a smaller idle air restrictor. Hope this helps. Corey you are definitely on track with your thinking good job.

[@coreykallmbah7580]

Thank you sir . I enjoy all your videos and appreciate your advice

[@robertbeckman2054]

I just need to know how much of those slits to be open, that's it. This was just too in-depth for me.

[@holleycarbshowtosadvice40y90]

.030 thousandths of an inch.

[@rooster68able]

Why does everybody talk about the transfer slot and never give us a number of turns from contact of the curb idle approximately 1 turn or 1/2 turn ? On curb idle ? Without having take of carb and look thanks

[@holleycarbshowtosadvice40y90]

You set your idle speed screw on the primaries to get the transfer slots in the right spot and then bypass air at the throttle plates to get your idle speed correct if you only need a slight adjustment, you may use your secondary idle speed, if you need alot of idle adjustment then you may need to drill bypass holes in the throttle plate butterflies, if so start out with small holes (.080) and go from there. Hope this helps.

[@stevoschannel4127]

You know a fella that has that accent knows exactly what he’s talking about

[@holleycarbshowtosadvice40y90]

That guy does talk kinda funny. Lol.