How to Set Idle Mixture Screws

People monkey with idle mixture screws way too much. Do they really know what they are doing? Here are all the details on how the system works, the inside of an Edelbrock carb and all the details you need to know to be successful. Edit: yeah I realized I said pound of vacuum. Oops.
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[@rustybritches6747]

Soooo much fun tuning carbs, it's a trial and error learning process especially if you're doing it with a butt Dyno and without an AFR gauge, but once you've messed around with them enough and you understand how everything works it's so much damn fun fixing peoples errors!

[@jeffschubert4715]

I enjoy watching and learning from you...needs to be more people like you...great job..always look forward to seeing new videos from you..

[@MuscleCarSolutions]

Wow! I really appreciate your kind words. I do it for fun and to hopefully help folks with their projects. Thank you!

[@ViktorBludov]

fantastic tutorial. thank you for explaining how things interact with each other. Without knowing how carburetor components work with all the adjustment screws it would be impossible to properly tune

[@felkerforcongress]

I really do appreciate your video... I have an edelbrock 4 barrel carburetor and had it adjusted on my 1986 monte ss, and when it gets hot outside and the engine warmed up, the car chokes itself and sputters when you hit the throttle hard. My mechanic adjusted last fall before I stored it for the winter and noted he adjusted it on the lean side. This showed exactly what i needed to adjust. Think I was running a little too lean. I ended up making slight 1/4 adjustments counter clock wise to both screws, and that so far seemed to take away that stalling away when I get into the throttle. Very informative and easy to understand.

[@MuscleCarSolutions]

Idle mixture screws aren’t in play past 1000 rpm. Keep the name in mind. IDLE. What you’re describing gets into the actual tuning of the carb. I’d verify the float level. This is where having a pressure regulator becomes critically important. Dial it in at 6 psi and adjust down from there. Make sure you have a spacer between the carb and intake to block the heat transfer. This time of year in hot climates need that spacer to block the transfer of the heat from the engine to the carb.

[@felkerforcongress]

I finally purchased a 3/4" Spacer from Edelbrock and it took care of my issues completely. No more stalling after car is up to temp, and starts with ease after its up to temp. Thanks again for the great info MCS!

[@kirklarson116]

Welp, this vid completely explained a problem that has been confusing me for years. I have one of these edelbrocks on my lightly built 283 thats in my 56 chevy truck. Slightly bigger cam, intake, headers and distributor and a bunch of chrome dress-up stuff. I couldn't figure out why I had to run my idle mixture screws all the way shut...it made no sense to me. It ran "just ok" but I could tell it was rich, I started playing with the metering rods and jets and got it the best I could. Well, today is carb rebuild day because the accelerator pump was leaking. Got it cleaned up and started back together but had to come in the house to get my glasses so I could read the jets and figured I'd have a beverage and watch a tuning video. I'm glad I did...you gave me some great information!!!

[@MuscleCarSolutions]

Good! If you have any questions, don’t hesitate to let me know. Always happy to help.

[@kirklarson116]

@@MuscleCarSolutions ​Thanks for the offer to help...not sure if I need help but maybe. First off, I have a 283 that came out of a 57 Chevy truck and since 1996 has resided in my 56 Chevy 3100. I had the machine shop do whatever they needed to machine just to clean it up for a stock rebuild. I wanted a little bit of a cam for a little bit of that sound. Have headers and an Edelbrock manifold from the late 90's. Got the rebuilt carb on today and went through the process of setting idle mixture and idle speed. It's idling good now and responds instantly to WOT. I have it idling at 780-790 and at that idle it's at 9.5" Hg. Now for the weirdness. I get tach and MP responses when I mess with the drivers side idle mixture but I can close the passenger side all the way and there's little difference in idle. My manifold is a square bore but it has a divider that separates the left and right side of the carb. This divider isn't sealed by a gasket...is this a problem? I am certain all ports and passages are clear. It's running good but I'm not sure it's running right. I've seen spacer/adapter plates that are installed between the carb and manifold...is this something I need? I'm a competent mechanic...just not totally competent in tuning with performance stuff. I look forward to reading your thoughts, Thanks, Kirk

[@diesel1586]

I love this because I’m in the process of replacing the old Qjet with a 1406 on my ‘85 K10 and I’ve been referencing these videos over the weekend, yesterday was the rebuild and mounting phase, today will be running the fuel line, I bought the Edelbrock line with the banjo bolt which I’m not too crazy about but hopefully it’ll work out. That being said, it does give me a little extra confidence to be able look back at some of the videos, so thank you for that

[@MuscleCarSolutions]

That was the whole reason I started doing these Edelbrock carburetor videos! Glad they’ve been useful for you!!!

[@vickikgibson9470]

This is such great information. You are the first one I found who actually shows how to use a vacuum gauge system to set it up! Now I will go get that so I can get a better set up on mine for my 85 Camaro I drive every day. One has to change things for winter vs summer driving!:) Thanks so much!!!:) Great job! Now all I have to do is figure out the throttle cable. My mechanic put a tie on it! Like whaaat!?? Now I have to replace or fix it better!

[@MuscleCarSolutions]

Glad it was useful! I try to be very through in these videos.

[@vickikgibson9470]

@@MuscleCarSolutions And that is really appreciated. People don't know that older cars will be needed, even if they are transferred over to other running systems. But being able to work on my own car over the years has sure helped me out. Living alone means you also have to be very self sufficient as possible. Information like this that is detailed, telling how, why and what to do MATTERS...A book can only say so much! Show and tell was always the best teaching method. So great job there buddy. I will recommend your videos and use this myself as I trim mine this spring:) I have one just like this! I learned to weld so I could rebuild my entire car. She is looking way better than me!LOL Cheers!

[@MuscleCarSolutions]

Something very satisfying about putting your hands on something and leaving it better than you found it! Thank you for the kind words. If you can weld, tuning a carburetor will be easy! 👍

[@robbroberts2180]

Great Video with commentary that is understandable for guys like me. C3 with a SBC 350 Edelbrock. Many thanks !

[@MuscleCarSolutions]

Cool! I know these make for longer videos, but I want to cover all of the “why” when going through the process. Very glad you found it useful.

[@bradsheap6474]

I just got me a new truck with a carbureted 5.7 350 and it’s idle is a little rough. I was thinking I needed to play with some screws but thanks to you I now realize I need to double check my fuel pumps and spark plug and even my air filter before I even consider messing with the carb. Thank you!

[@MuscleCarSolutions]

Timing!

[@bradsheap6474]

@@MuscleCarSolutions ya I’m hoping it’s not timing or imma have to recruit my uncle to help me out with that lol

[@MuscleCarSolutions]

@@bradsheap6474 timing and carb tuning are done together.

[@cutl00senc]

Now we need a video about setting initial ignition timing and what to do about vacuum advance. Great video!

[@MuscleCarSolutions]

It’s coming. Just waiting on an engine to get out of the machine shop. Hopefully in try next month or two. Thanks for watching!

[@AZHighlandHomestead]

@@MuscleCarSolutions have you made this initial ignition timing video yet?

[@nursecuenca]

On my edelbrock carburetor, vacuum manifold hose goes toward transmission. Is that port where I place vacuum gauge? I'm learning about cars from watching your videos.

[@cutl00senc]

@@nursecuenca vacuum gauge can be attached to any port on the manifold. I use the port on the carb in the front on the lowest level closest to the manifold. Should read high at idle and drop on rev ups.

[@GarrettGaina]

I've watched this and your dual quad video recently and I feel like I've learned so much. I've been helping my dad wrench on his 1962 Chevy Impala after many years of sitting. He's had the car longer than I've been alive and I'm happy to finally be able to work on it with him after being generally useless when I was a kid, lol. It's a dual quad 409 with 650 cfm edelbrock's. It's bored .030 over from a previous rebuild, has lower compression pistons, and my dad said it has a bigger cam than stock. I got it timed better earlier this year, about 35 degrees total mechanical advance, but I don't remember the initial timing. I had the idle mixture screws set for around 1.5 turns, but we can't get it to idle below 1400-1500rpm. I've got it in my dads head to put a fuel pressure regulator in the system and to pick up a vacuum gauge so we can get accurate readings. He was just happy to get it running better than it was this year and wasn't interested in pulling the carbs to see if we were engaging the transfer slots or making any other heavier adjustments. I know there are a lot of unknown variables in this rambling paragraph, but do you have any tips for helping a dual quad 409 idle happier?

[@MuscleCarSolutions]

I think you’re on the right track in verifying the transfer slots aren’t exposed. Easy job to pop the carbs off to verify. Then you know your starting point with the carbs. Verify the fast idle cams aren’t engaged on either carb. What is your engine vacuum at idle? What step up springs do you have installed? 650s are w bit aggressive for a low compression engine so you’ll likely always fight a rich condition. Start with the above and see what you can discover.

[@GarrettGaina]

@@MuscleCarSolutions I don't have many answers for you. Unfortunately my dad has the car put away for the winter now as it cools down here in Michigan. I appreciate the response I hope to get on the right track in the spring.

[@MuscleCarSolutions]

@@GarrettGaina if you’re using ethanol added fuel, make sure you drain the carburetors and put an additive in the tank to keep it stabilized and as much of the moisture out. This is what I use for long term storage. amzn.to/3vyT29A

[@db3170]

Vacuum leak my guess

[@BPattB]

Thank you great job just picked up a use Edelbrock 1406 and and the transfer slots were exposed all the way. The idle screw wasn't even touching anything, I backed off the fast idle screw and watched the transfer slots disappear. This is a great this is a great video for someone that's about to put a used a Edelbrock on their car!!

[@MuscleCarSolutions]

Glad it was helpful!

[@BPattB]

@@MuscleCarSolutionsyour videos are what KZbin used to be, and still should be. People with an area of expertise giving their opinion and help!

[@MuscleCarSolutions]

Very much appreciate your kind words. You’re the exact reason why I decided to make these videos. Couldn’t be happier it was useful for you. Thank you!

[@BPattB]

@@MuscleCarSolutions 👍

[@rubenfraire8926]

I will try it in the morning .thanks will go through your steps

[@hvspeed6102]

Great video. One question I can’t seem to get answered. Doing all of what you’ve shown, I end up with over a half turn difference between sides, in order to get the best readings/ idle quality. Is that normal? Stock SBC 350, essentially same stuff you’re working with. Runs fine, just always hear the two screws should be adjusted the same number of turns. I just replaced my older Edelbrock 600 with a new AVS 650, both carbs were the same way, 1 1/2 turns on one side, 2 1/4 the other. Thanks.

[@Procrastn8rsUnite2morrow]

Perfect tutorial for me. Thanks so much!

[@timgiesin4025]

Very good video you did a outstanding job explaining what you are doing and showing what you are doing

[@b-17wingman37]

The cut away is really helpful. Thank you.

[@MuscleCarSolutions]

Thank you! I’m really glad you found it helpful.

[@rallyechall3827]

Another awesome video. WIll use these tips and knowledge to tune my car when the assembly is complete.

[@MuscleCarSolutions]

Nice! Well don’t hesitate to ask any questions along the way. I don’t mind helping where I can. What are you building?

[@turnipsucks6416]

I'm a newbie at this, and the video is fantastic. Will be practical applicating this to my kids car soon. Thank you!

[@MuscleCarSolutions]

Glad it’s helped! Just let me know if you have any questions and I’ll do what I can to help.

[@turnipsucks6416]

@@MuscleCarSolutions Sounds great. Thank you.

[@superdave103harley]

Still one of my favorite videos! Excellent brother

[@MuscleCarSolutions]

Thanks! Glad you liked it!

[@stiefbeen22]

I assumed the engine was rather new/fresh, but this explains it. Thanks for the video and your reply.

[@MuscleCarSolutions]

Its fresh now! That poor old small block was worn OUT! I’m surprised it ran as well as it did.

[@1badombre82]

Super helpful! Will be doing this after I reset my timing this weekend. And I'm glad you told me to check the metering needs after. And as always I gotta make a joke. "Don't be that guy that's always playing with it" yeah yeah my girlfriends always saying that too 😅

[@dgiorgi1725]

Now this is the video I need to see, thank you. Great information content here.

[@oleandreasjensen5263]

THANK YOU. You are an awesome teacher . - Its awesome to learn so much as I do with support from your videos.. Love these Edelbrock Carbs.

[@MuscleCarSolutions]

All I can do is show it. You’ve got to apply it and so the work so good job!

[@oleandreasjensen5263]

@@MuscleCarSolutions Well, In my opinion you do so much more than to show how these carburators works. Thank you for the insight I have learn from your very well done , and highly valued videos. Best greetings from Norway : )

[@MuscleCarSolutions]

@@oleandreasjensen5263 very much appreciate the kind words. Very glad these have been useful for you!

[@raylewis5570]

I'm trying to get this downloaded in my head. So I can be confident on doing this like normal. Thanks

[@MuscleCarSolutions]

Once you spend a little time hands on doing it, you’ll pick it up pretty quickly.

[@ryankennedy9414]

Great video. I used your guidance today trying to sort out my 1406 on a 1980 Dodge 318. The truck was given to me so I don't know the cam, but initially I thought it had some lope, but after some tuning, maybe not. Has long tube headers, that's it. We had issues once warmed up, at a stop in gear the truck would start to lurch against my foot on the brake, to the point where it would eventually stall if I didn't shift into neutral. This only started when I had the transmission rebuilt, I assume as it no longer had the slip the old one did. I did the screws all the way in, then two turns out, and backed the idle down and it was much better. Vacuum over 19 all the time. It still has some issues though, which I was looking at your other video about tuning charts on. I personally thing the 600 is a little overkill for this engine, and I am guessing its running rich. It smells rich, and at any throttle off coast you hear small backfires within the exhaust. I am just ordering a timing gun with RPM so I can do this idle tune more correctly (going by feel right now) but this sure did help alot. I did notice, when screwing in and out to find the limits where it started to stumble, it definitely does way out, or nearly in, I found the range in between hard to choose. It seemed between those two point there was good two turn of screw adjustment that didn't alter the RPM or vacuum so I was a little stuck on where to leave it. I am looking for cruising, and thinking its running rich I went on the lean end. Thanks for the great video!

[@MuscleCarSolutions]

Yup, that’s entirely possible. It’s kind of on the edge of being too big. If you look at the video on how to select a CFM, you’ll see it’s probably close to one or the other. I think if you’re honest about the max rpm, it will probably point you at the 500 being a better size. But you’ve got the 600, might as well run through the tuning chart and see how good you can make it? Sometimes it’s tolerable once you get it dialed in. And for sure, there is always a point where no matter what you do, it doesn’t get better. That’s usually your time to lock her down and go have fun!

[@ryankennedy9414]

@@MuscleCarSolutions Thanks. I forgot to mention, while I had the Vacuum gauge on that port, the EGR valve had no vacuum and the engine seemed happy, but when I put the vacuum line back on the EGR the idle went more choppy. It seemed like the truck was much happier with no vacuum on the EGR. Any thoughts? I sorted adjusted around that so it was sounding happier when I put the vacuum line back on, as setting it perfectly without it meant it didn't run great when I put the line back on.

[@VinoRatRodbuilds]

Thanks for sharing this! Great info thanks again!👍🏆

[@MuscleCarSolutions]

Thank you! Very much appreciate you watching! 👊

[@mintypotato777]

well explained. would like to know how you mounted your fuel pressure regulator. looks really clean right there. so clean i cant even see how its attached lol

[@erica8664]

Thank you for your time and expertise .

[@MuscleCarSolutions]

You’re very welcome! I’m always hopeful these are useful to someone. Thank you!!

[@HectorGonzalez-db3mz]

Very well explained and so easy after watching your video..tkz.

[@MuscleCarSolutions]

Nice! Glad it was useful for you!

[@clenchedfury6019]

Thank you for the in depth info🤘

[@cbb_joker24dpmotorsports61]

By far 1000% this video has helped me the most I appreciate you going from top to bottom with this and all the in-betweens❤ thank you!!!

[@MuscleCarSolutions]

Nice! I’m glad it was useful! Thanks!

[@lyleleavell6200]

What about secondaries activating to soon? Is the weighted vacuum secondary sufficient to prevent premature secondary opening? I may be attributing a part throttle bog/gasp to the wrong system in the carb.

[@brycedelaney4301]

I'm about to start my sbc for the first time with the distributor roughly set and the carb. I haven't ran this edelbrock before so I don't know what to expect. Any tips on how I should go about the first start of the engine with rough timing and carb?

[@jackn5048]

Do the holley 4bbl secondary's add any fuel or air in the idle circuit? Or is the entire idle circuit fueled by the primaries only?

[@AGClassicCarTuning]

Great video and as ever very informative. Are the transfer slots visible when the carb is fitted? I'm just thinking in terms of how to know if the transfer slots are exposed or not when the idle mixture screws are seemingly not effective. on a 383ci if I lift idle to 1300 or 1500rpm I have a nice steady vacuum at 20"Hg, but when I bring the idle down to 850/900 rpm it's an unstable 15 to 17 Hg". No effect on CO readings, Vacuum pressure or idle speed from the mixture screws so I'll be cleaning the idle air mixture screws and holes tomorrow with carb cleaner / compressed air and careful piano wire however if it's not effective I want to be able to confirm or eliminate the transfer slots being too influential and over powering the idle mixtures involvement. Cheers...

[@MuscleCarSolutions]

What’s your engine idle rpm? That will give a better idea of where the carb is currently sitting in regards to the transfer slots. And as a bonus, I just released this video yesterday on the transfer system; kzbin.info/www/bejne/eqG4aKOMabGcaaM

[@hybridmusclegarage4590]

Great video, and info! Thanks

[@MuscleCarSolutions]

Thanks man. Appreciate it!

[@Brian-lu3tf]

What do you do when due to cam, ect, in order to get the idle where it needs to be(950 in my case), the idle speed screw has be far enough that the transfer slots are exposed? I know on Holley's I can set the secondaries cracked, and that helps with that, and in extreme cases in the past, drilled holes in the throttle blades...what about on the 1406 AVS? The overlap on the cam in this engine (350 chevy, prior owner installed a pretty hot cam, not sure what the specs are), and I am pulling a max of 12.5 inches of vacuum...Got the initial advance on the HEI at 14 degrees, total advance 38, all in by 2800...if I advance more the idle goes up, but so does the temp...so I cannnot really go much further...I have a vacuum advance that adds 10 degrees at idle as well, so with that hooked up, I am idling at 24degrees. I have heard everything from drill small holes in the plates like we used to on holleys, to adding a vacuum bleed to the PCV or Full Vacuum port(right now feeds the HVAC system)...right now, I turn the carb over after getting it idling as good as I can at 950, set the mixture screws best I can using vacuum guage, I get very little effect, and almost half the transfer slot is exposed under the blades...

[@joshdavis1257]

Brilliant. Thank you!

[@daledyer3741]

Great information. Thanks

[@MuscleCarSolutions]

Glad it was useful to you!

[@taylormach1699]

A lot of info, I did not know. THANKS.

[@MuscleCarSolutions]

You’re very welcome.

[@rodolforios1057]

thank you for this video i learned a lot from it, and look forward to studying your other videos

[@MuscleCarSolutions]

Let me know if you run into any questions as you’re tuning.

[@raymondmoreno7442]

Thank you for a great video really helpful

[@MuscleCarSolutions]

Awesome! Thank you.

[@Wikkus]

Hi man! Great video, very useful. I've not had an Edelbrock carb before, but now I have one (a 1406) and I'm having trouble with it idling very rich (like eye-watering-standing-next-to-a-nitro-motor rich ;) ) My first step was, having read the manual and watching a couple of your other videos, to install a fuel pressure regulator -- this motor came with a non-stock Carter 0-2208 pump which, from what I gather, is most often used on marine motors. It was delivering 6.5psi, so I wound it back to just over 5, but it's still running rich. The motor is the original 350, but I don't really know the history of it and haven't opened it up to peek inside. What I do know is that it has an (older) Edelbrock Performer manifold, a pair of Trickflow aluminum heads, some long-tube headers, an MSD 6A, MSD billet dizzy, MSD coil. Cam is unknown, reciprocating stuff also unknown. Was seeing ~15"Hg on the vacuum gauge when I hooked it up, and it's running ~32deg total advance. My next step is going to be to pull the idle mixture screws out and check them. I don't have compressed air -- I'm just a guy with a single car garage -- would canned air suffice? Any other ideas gratefully accepted.

[@MuscleCarSolutions]

Before blowing through the idle mixture screws, I’d pop the top off and check for debris in the bowls. Blow through the needle and seats. Adjust the float level lower. Then blow through the idle mixture screws. Check the electric choke setting. Reassemble and check again.

[@w2tty]

Good video, thanks.. I once had a friend's engine backfire when I snapped the throttle and the piston and spring shot out. The spring went down into the carb secondaries! Thankfully it did not go into the engine but laid on the throttle plate and I was able to retrieve it with a magnet. But I sure did panic there for a minute. I'm hesitant to try that again.

[@MuscleCarSolutions]

Ha! That’ll wake ya up quick! Good thing is with no load on the engine it’s not possible for the secondaries to open up. But it will sure get your attention!

[@CCAutoWorks]

Great info thanks for sharing

[@MuscleCarSolutions]

Cool. Thanks man!

[@williambissell5943]

EXCELLENT VID, THANK YOU!!!!

[@rmpge]

Great information 👍

[@johnnyturbo8460]

Great and to the point video! Thanks

[@MuscleCarSolutions]

You’re very welcome. Thanks for the feedback!

[@johnnyturbo8460]

@@MuscleCarSolutions 😁👍

[@johnnyturbo8460]

@@MuscleCarSolutions I just noticed you have Merch.. I had no idea... I like and will be buying the "just because you don't know how to tune it, doesn't mean it's junk" shirt Thanks to your videos, I am truly enjoying tuning my Edelbrock AVS 2 650

[@metropdmhatt]

Thanks so much! Does it matter what side of the carburetor to plug-in vacuum gauge? I get different readings, depending on which one. I may have a cracked header.

[@MuscleCarSolutions]

8:40 in the video tells exactly what port it goes to. Full manifold vacuum. If the gauge reads zero vacuum, there’s no reference point to adjust.

[@AndrewPhillipsqualityassurance]

Thank you for this ❤

[@fairlanephantom]

Transfer slots used to mess me up. Another thing I've come across is that highest vacuum isn't always the best goal for tuning. I've had better luck shooting for closest to stock settings. Spec on my engine is 19/20 inches in park, it can make 24 inches at vacuum, but you end up over compensating elsewhere to make that possible. I'm fine with just setting it to spec, I don't want to beat on an almost 70 year old engine too hard.

[@MuscleCarSolutions]

There’s something to learn from this. Sometimes a final setting at the highest vacuum is not the best. That can also reduce power and torque. There’s a happy medium here and one that isn’t always evident at the time of adjustment. That’s why it’s best to spend some time driving it to see how it feels and if an adjustment needs to be made one way or another. Good points!

[@fairlanephantom]

@@MuscleCarSolutions Yeah. Have some confidence in your adjustments or you'll never get out from under the hood.

[@davidhaxton5050]

Great video for helping people like me who are not great at all this tuning stuff!

[@MuscleCarSolutions]

That was the entire reason why I started this channel in the first place. It’s not difficult. Just need an explanation and you’ll find out you’re capable of it! Thanks for the feedback. Much appreciated.

[@dldldl8028]

Thanks a lot, great vid! Helps me a lot

[@MuscleCarSolutions]

Awesome! Don’t hesitate to ask any questions along the way. Happy to help if I can.

[@blackforestvintagefords7872]

Thank you - that helped much!

[@markmontes3469]

Amazing video! I’m 22 Tryna to learn how to do this on my c10 not many people in my area can do it.. If you do have a big cam, headers, intake etc, how much vacuum should you reach for? Also the springs bounce up and down on idle. Could it be the springs like you mention or the truck being not tune correctly? Thanks again!

[@MuscleCarSolutions]

If the springs bounce at idle, then you have the wrong ones. Measure your full manifold vacuum at idle and match up the corresponding spring. How much vacuum you can achieve is a moving target. Your engine will tell you what it’s capable of.

[@markmontes3469]

@@MuscleCarSolutions thank you big time! So I need to try to get the highest vacuum I can get. Going to try and re tune it since my idle has been dropping after I did a burn out.

[@jennysmith3224]

I enjoyed your videos 👍 Is there a way to know if the transfer slots are exposed with carburetor already installed? 2nd question , Why is there two air fuel mixture adjustment screws. 3rd question The carburetor we have only has a vacuum tub going to left slot and right slot is closed off. Son insisted on buying 1984 Chevy s10, Small block, serial number is faded. Stripped down to just engine and carb. Help please

[@MuscleCarSolutions]

Well it’s a bit of a guess but one way to know almost for sure is if the idle speed is around 1000 rpm. Other than that, remove it and confirm and start the fix. Thanks for watching!

[@danielbaker8865]

great video

[@dennishouk4630]

That little torx bit coming off the driver could have caused some heartburn😊

[@MuscleCarSolutions]

0% chance. At idle, throttle plates are closed.

[@dalejohnson3520]

Would you also use a air/fuel ratio meter to help with the adjustment. I use one on each bank to ensure that both sides are balanced and also use a thermal reader to check each cylinders temperature so that you get the most out of each cylinder. This also tells me if there is a weak cylinder so that I can correct an issue earlier instead of having a bigger problem later.

[@MuscleCarSolutions]

You certainly can but with a simple idle adjustment it’s really not necessary. If you see something way out the norm as far as lean or rich goes then you can compensate. But using a vacuum gauge is generally the easiest, safest way. Love the AFR for the rest of your tuning though!

[@Asphaltsquadron]

Awesome, thank you I learned a lot. I notice your fuel PSI gauge is indicating well below 6lbs? I have a stock Chevy 350, performer manifold, headers, and a Edlebrock 1406 (600 cfm) most I've read thus far mentions 6lbs is optimum. Can you elaborate? THANKS!!!!

[@MuscleCarSolutions]

On an Edelbrock start at 6 and tune down from there. There is no “optimum” setting. I usually run 4.5 - 6 as the range. The engine in the video is a mostly stock 350 with intake and headers with a 500 CFM carb.

[@Asphaltsquadron]

@@MuscleCarSolutions Thanks for the reply, Very MUCH appreciated! I have the same basic set up, do you feel that a 650 is too much? I will likely never upgrade. I also have a Edelbrock 1406, would that be better suited to run with my current setup?

[@MuscleCarSolutions]

@@Asphaltsquadron only you can answer this. I did a video on just this topic to help you make that decision. kzbin.info/www/bejne/fqqXpGx4aZiMg5I

[@deankay4434]

You have to begin cold to check choke operation, linkage to fast idle cam and adjust as needed to factory AFB settings. Check timing chain condition while rotating crank to TDC, backward while watching rotor. If 0-10, some wear, if 12-16 replace, if 15-16 or up, it can jump a tooth. If fresh paint, run compression test, cylinder leakage and adjust hydraulic lifters both roller and flat tapper at zero lash on push rod up only, not spin or rocker wiggle, then tighten 1 1/2 turn to place the plunger pistons in the lifters bore. Then place on 8-10 degrees BTDC on power stoke. With key on, engine off, "ST125" or other spark tester in wire #1, retard distributor and slowly advance until spark occurs. Tighten distributor and use timing light. It is just left of the die cast Tach-Dwell Meter in the tool box on top of the 7 distributor wrenches. Have a nice day. DK, ASE master tech since 78, retired.

[@rksg2003]

What are those spark plug wires? Great Video!

[@Wazoo117]

great video, but one question. how do you go about adjusting a reverse idle carb? like a Holley 7508

[@MuscleCarSolutions]

I’m not familiar with that carb. Is it one of the OE two barrels.

[@mickangio16]

@@MuscleCarSolutions there were Holley 4 barrel carbs from the emission era that the idle mixture screws adjusted the amount of air admitted to the idle circuit instead of how much fuel mixture that was admitted. Turning the screw out leaned the mixture. Turning the screws all the way in was as much as you could richen the idle mixture. I think I got a couple of them working satisfactorily many years ago by richening the secondary idle bleed circuit a bit to make up for the lack of adjustability. My opinion- don't bother with it unless you are a tinkerer and familiar with Holley carb. I think they may have used different metering block gaskets, too, which would probably be very hard to find now.

[@stephencrisci2905]

What color springs n metering rods should be in carb for stock 5.7 dual exhuast...stock cam...😊thank you..good video helpfull...

[@MuscleCarSolutions]

There is no set answer. Make sure the carb is to the factory settings and start tuning. Springs depends on your engine vacuum.

[@jessestone4650]

Question: if u are using a spacer/ elderbrock heat insulator spacer, should you richin up the mixture a little bit? Example get the most vacuum, for the best lean condition, and then Richin just a bit?

[@MuscleCarSolutions]

Reset if you feel it’s necessary. The engine will tell you if it wants more (or less) fuel. Remember idle is just a condition under 1000 rpm. Once you’re past that, the idle circuit is no longer metering the fuel the engine needs.

[@joshuaatkins5197]

Great refresher! There's a reason I don't use multi-purpose screwdrivers with attachments on carbs though. It's hard to drop a hole screwdriver down the throttle blades but a screwdriver tip? Bye bye. Also thank you for not playing obnoxious music while you're trying to explain this.

[@MuscleCarSolutions]

It’s at idle. Throttle plates are closed. Zero worries.

[@joshuaatkins5197]

@@MuscleCarSolutions guess I was thinking they aren't always closed in every situation and dropping something down the carb is never a good situation 🤷‍♂️ so for people learning ( what this video seems to be aimed at) it might not be a good habit. Happy Sunday 🍻

[@73ac39]

I'm enjoying all your videos,very good,very informative. I've got an issue maybe you can help I'm lost here. I've got a sbc in my Monte Carlo. Usual 30 over 350 with vortec heads and a comp cam holley 750 vs, msd billet hei. Car runs and drives well. I set idle 850 rpm but it will change,at times I will see 1,000 rpm (in park) or 650 rpm. Is this fuel pressure issue? It's done this with 2 different carbs 2 different dizzy's. Can't figure it out. TY !

[@MuscleCarSolutions]

Could be a number of things. Sometimes it’s carb related, sometimes it timing, internal engine related. Start with the east things and work your way from there.

[@73ac39]

@Muscle Car Solutions HI. Yup you were right. Seems the throttle return springs were binding with each other. Got it fixed. Thanks.

[@MuscleCarSolutions]

Glad it was something simple! Good work!

[@Wahayawolf73]

Great info thnx

[@danielworden4695]

I have a 318 that's all stock has a hei. Ignition on it it idles really smooth only thing it smoke when I first cold start it .but after 2 minutes it's all good .2280 stock carborator

[@Diamondsintherubble]

So I’m new to tuning carburetors, I haven’t done one myself yet but I’d like to convert from efi, but would setting the idle higher like maybe 1100-1200 rpm cause issues with the fuel slots you mentioned or would I still be in a “safe” range? I ask because if the cam chops too hard for 800rpm, raising it would maintain the idle

[@MuscleCarSolutions]

Yes, anything higher than 1000 rpm and you’ll bypass the idle circuit and be into the transfer slots. If you’d like to check that, set your idle at the 1100-1200 on the car and then remove the carburetor. Flip it over and if you can see the transfer slots, you’re no longer on the idle circuit.

[@Diamondsintherubble]

@@MuscleCarSolutions okay perfect. Thanks for the solid advice

[@lazydaze9947]

On a Holley, some people say to crack the throttle plate so that you can see a tiny square of the transfer slot or about .025" of it. Then tune idle screws from there. Would you recommend to do this with an edlebrock?

[@MuscleCarSolutions]

Too many variables. There is no one setting for all. Doesn’t matter the flavor carburetor. I wouldn’t recommend that setting unless I knew the combination.

[@jeffpowell2467]

Thanks for reply🤓

[@mrkwllms340]

I’ve enjoyed your videos. Just one question. When my AVS came out of the box, the idle mixture screws were fully seated (closed full right). On the BG carb the directions stated to open the idle mixture screws two full turns , then start the engine and work towards turning right (lean) to get the engine to run rough, then adjust back towards rich. Is there any guidance as to where I should process with my idle mixture screws?

[@MuscleCarSolutions]

On an AVS? 1 1/2 turns is a good place to start. Its plenty to get it started. First thing we talked about in the video is timing. Not sure what engine you're working on, but getting some timing in it will help you adjust the idle mixture and start the tuning process.

[@mrkwllms340]

@@MuscleCarSolutions I have 12degrees on a 73 Mopar 340. Thanks for the answer. I’ve been looking for a starting point to reference. I used 2 turns because that is what BG recommended for the Demon. 1 1/2 would have been faster.

[@MuscleCarSolutions]

Don’t be afraid to add more timing!

[@neilbrackstone6923]

Great video sir...I'm 2 days away from attempting this very deal however I noticed as my 350 is bine stock other than an I take and headers do I or would u recommend a pcv valve as of now I have not installed one thanks

[@MuscleCarSolutions]

Yes absolutely install the PCV. You need the crankcase evacuated to avoid further problems.

[@neilbrackstone6923]

@@MuscleCarSolutions thanks a ton for the info definitely subscribing to your channel

[@MuscleCarSolutions]

@@neilbrackstone6923 anytime. Always happy to help.

[@romac2534]

At the 9min mark I noticed the carb has a happy face at that angle, kind of looks like Rick lol. Anyways been watching your videos they are very helpful, thank you!

[@MuscleCarSolutions]

Happy they have been useful for you! Thank you.

[@jordanisles9767]

Any thoughts about a ford 400 mild build nothing crazy 1406 carb always stinks of gas but recently I added an electric pump and it idles rough in gear but smooth as butter in park or neutral and runs great driving around. I noticed it before the electric pump but I’m seeing about 800-900 idle in park

[@MuscleCarSolutions]

All the normal things. Timing. Fuel system set up. Fuel pressure. Junk in the system/bowls.

[@oldmanintheshopbuiltnotbou8726]

Great info

[@MuscleCarSolutions]

Thanks!

[@GOTTACO]

You are a life saver!!!!!!!!!!!!!!! Thank you soooo much for this video!!!

[@MuscleCarSolutions]

Glad you liked it!

[@bobbydelamar606]

Great video. I need to tune up my 1970 Roadrunner with the 383. It starts and idles but it's hard to get it there. The exhaust burns my eyes. I just got the car so don't know everything about it. Sounds like it has a bigger cam. It has a 4 barrel Edelbrock and the mixture screws don't seem to effect it. I have not put a vacuum gauge on it yet.

[@MuscleCarSolutions]

If the mixture screws have no effect, you’re into the transfer slots. Nothing you can do until you fix that and get the idle down. What’s you’re initial timing set at?

[@bobbydelamar606]

@@MuscleCarSolutions I dont remember, It's been awhile but timing I think is at 8. What's a good set point? I've been fixing a few things on this car from the previous owner. I found a rag wrapped around the oil pick up tube!! Probably when they messed with the cam.

[@bobbydelamar606]

@@MuscleCarSolutions I'll check the timing again. The vacuum advance wasn't hooked up to the distributor. I think I have it right now.

[@MuscleCarSolutions]

@@bobbydelamar606 8? Go 12-16 initial. Guess we need to start at the beginning. What’s your fuel pressure regulator set to? 4.5-6 is your best target range.

[@bobbydelamar606]

@@MuscleCarSolutions Okay I'll recheck timing again. If it's mechanical fuel pump, is it the same procedure for checking pressure?

[@db3170]

Digital tach a must adjust air/fuel mixture for maximum possible rpm then readjust idle screw then readjust mixture screws for maximum rpm then readjust idle screw again down ultimately closing the butterfly and creating high nozzle velocity and remember to fatten up for cooler temps

[@tnposeys]

I have a new carb on my 78 Ford F150 351M. It's a 650 EVS2. When I turn the idler screws in, the rpm don't change and it doesn't kill the motor. On both screws. So, sound like you are saying I may already have some trash in the little slots. I guess I can take it off and check that. I do have a new tank, lines, and pump. But, it did have the old tank when we first tested it and noticed there was rust in the tank, so we changed all the fuel lines and tank out. I guess there could be some trash in the carb from that. When I idle and the engine has been running about 30 minutes, it surges a bunch off of a stop light. So much that I have to put on my emergency flashers for a bit until it gets back to running normal.

[@MuscleCarSolutions]

I’ll link a video that you’ll find useful. kzbin.info/www/bejne/eqG4aKOMabGcaaM

[@Vxc6]

Once you done you done , this engine is done 👌🏽😎

[@dynamike7108]

If you put the vacuum gauge on the ported side to begin it will tell you if the transfer slots are closed. No vacuum means they’re closed. I usually screw the idle adjustment in to get max idle with no vacuum. Then I know I can always turn the idle down but not up

[@camerinsmith5182]

Man you make some awesome videos!! Can you do one on setting time on a sbc with hei?

[@MuscleCarSolutions]

Thanks! Yes that’s on the list of ones to do but I’m waiting for the rebuild on the small block in the GMC before I shoot that one. Going to be a few months when the weather gets a little warmer. Thanks for watching!

[@captainshimmer7319]

Hello so the transfer slots are those little rectangular holes and I want them exposed before tuning the carb?

[@MuscleCarSolutions]

You want them covered by the throttle plates. Exposed will introduce fuel and bypass the idle circuit.

[@guillermocastillo3833]

Great info, as always. I have a question - finally got a fuel pressure regulator installed on my engine, and decided to start tuning. I have the AVS 2 with a 1" 4 hole spacer on a SBC 355, Comp 262-XE, Brodix IK180, about 10-1 compression, dual plane intake, headers, 2.5" dual exhaust w/h pipe if this info helps. Also has MSD ignition with a recently replaced cap and rotor, wires and coil. Initial timing is set at 14 BTDC, haven't checked total timing. Tried a bit of tuning with advice from your videos and had fair amount of positive results, but daylight got away from me and I had to call it a day until next time. As you say, this is a process. My last adjustment, and only one changing rods or jets (so far) was to try number 9 on the calibration chart. The engine responded well at WOT, but the idle went up, and at idle it sounded a bit rough. Is this the time to adjust the idle screws? Thanks for all your assistance!

[@MuscleCarSolutions]

Yes it’s typically a back and forth game making adjustments at different points in the system. Once you make an adjustment (like a rod and jet change) it’s not uncommon to make others you already adjusted. Accelerator pump, AVS door, fuel pressure, timing. It’s a balancing act. It’s also why it takes so long and people give up too soon.

[@guillermocastillo3833]

@@MuscleCarSolutions got it, will keep plugging along! Thanks, and I have a beer heading your way! Cheers 🍻

[@MuscleCarSolutions]

Sounds like you’re on the right path. Don’t hesitate to let me know if there is anything I can suggest during your tuning process! Much appreciated!

[@guillermocastillo3833]

So I had the carb off today and checked out my transition slots. They were exposed quite a bit so I adjusted the idle scew to just touching the cam. The car would not start and I had to adjust the screw in quite a bit. I have the 650, should I have gone with the 750? Maybe another issue?

[@MuscleCarSolutions]

@@guillermocastillo3833 not with that tiny cam. Start with the simple things. Dial the timing back. Search for a vacuum leak. Verify float settings and what pressure the carb is seeing.

[@frankg5177]

Great video but have a quick question, I have a big block Buick with a good sized cam 469 lift at 268 duration, Edelbrock 750 with Edelbrock B4B manifold with Headers the best I can do is 17" of vacuum timing is set to 15 deg at idle (no vacuum advance and I get a lot of needle bounce on my Vac Gauge assuming that is the cam, any thoughts on this situation?

[@MuscleCarSolutions]

Step up spring! Change to match that 15” of vacuum at idle. What’s happening is the spring is too light.

[@frankg5177]

Great I will open the hatch and see what they are doing and order a tune kit

[@frankg5177]

Forgot should I expect to see them sucked down or floating?

[@MuscleCarSolutions]

@@frankg5177 at idle the pistons will be down and steady there.

[@porterpowerrotary7619]

Instead of a vacuum gage can u use afr gage?

[@anomalous9448]

Thanks for this video. I noticed you are running the vac gauge off of the carb port. I have been using my manifold port. Can you explain the difference?

[@MuscleCarSolutions]

Yes. The vacuum gauge is there to measure the engines vacuum while you make your adjustments. The manifold vacuum port is below the throttle blades of the carburetor and will read full manifold vacuum. The timed vacuum port is located above the throttle blades. At idle when they are closed, no vacuum is registered. So to make the adjustment, you need manifold vacuum. .

[@anomalous9448]

@@MuscleCarSolutions thanks for the clarification. I have been using the manifold port for tuning but still my car runs rich with a strong gas smell. I tuned it for the highest vac reading (22) but I think I will back that off to 20 and see how that goes. Again, thank you for responding.

[@MuscleCarSolutions]

@@anomalous9448 setting idle isn’t tuning. Once you have that basic setting done, NOW you can start the tuning process to get the best performance and get rid of that rich condition.

[@stuckinmygarage6220]

Ditto on the learning. Thank you. Here's one I think means something to an expert: I *think* I got it good enough to drive along. Then, I pull the brake vacuum hose and she ups 50-100 RPM?? Am I running rich? E-1406, mild Comp cam, 440, elec '74 ignition. Thanks.

[@MuscleCarSolutions]

It’s possible. Typically when more air is added one of two things happen. Runs rough or speeds up. 100 rpm is pretty noticeable. If you feel like it is getting a little too much fuel (assuming it’s at idle where taking about), you can add a little bit more timing and reduce the idle speed and or mixture screws. Just kind of a little trial and error type of thing but shouldn’t take too much time or effort. Here’s where an AFR really earns it’s money. You’ll know exactly what the output is and can quickly determine if your adjustments made the right changes. But in this case, I’d it starts easily, idles ok, doesn’t smell too rich and everything else is good, then I might not mess with it. But it’s a great observation!

[@raybinker9472]

At 14:02 my butt puckered seeing the bit stuck in the torx when her was checking the plunger springs...omg my heart skipped.. I had a helper years ago I was teaching on a bigblock in my Barracuda and he dropped a bit down the carb and BOOM new motor that just got broke in had to be RE Built again..ouch Great video btw!!

[@thorstencoates9255]

Question! For a 360 5.9L V8 small block. What size jets do I need for the carb. 0.107 inch, 0.098 inch or 0.089 inch jets.

[@MuscleCarSolutions]

Follow the tuning chart. Don’t make arbitrary jet size changes. Leave the stock rod and jets in and follow the changes on the tuning chart. I promise you that the results will be a lot better than making random changes.

[@chicanoperez6377]

I noticed you had a spacer between the intake, manifold, and the carburetor, does that really help with warm start ups? Can you give me the part number for that? Thank you.

[@MuscleCarSolutions]

If you look at my other videos, I did one on heat soak and all the part numbers are in the description. Makes a big difference.

[@evelynlopez669]

what are you pointing the timing gun at when your checking your rpm? at the distributor? is it wireless?

[@MuscleCarSolutions]

Not pointing it at anything. Using it to show the engine rpm.

[@cesarguzman6346]

I just got a new edlebrock preformer series 750 cfm, and I looked under and saw that the transfer slots were very exposed. I turned back both the idle and fast idle screws and nearly backed them out, but the transfer slots are still slightly exposed. What do you think that could be?

[@MuscleCarSolutions]

Could be a number of things. Bound somewhere. Return spring is weak/out of alignment. Getting stuck on the choke mechanism.

[@alfredovegacortes777]

Hello Sir I have a question about a 4 barrel carburator on a 1985 winnebago itasca motor home it has the 7.2 engine on it that it doesn't pass the smog check as it seems the carburator is using too much gasoline, is there an adjustment to reduce the amount of gas the carburator uses ? thanks

[@MuscleCarSolutions]

Unsure what engine that is. Factory stuff is usually pretty simple. If there’s a problem, it’s not usually an adjustment. It’s determining where the problem is. Rebuild. Filters. Garbage in the carburetor.

[@MrCbell57]

My new Edelbrock AVS is whacked. I can turn my mixture screws all the way in without any change in motor response. Nor does moving them out change anything other than it runs very rich. I’m thinking there is an issue with this brand new carb since it’s not adjustable. Ive got it about 18 in vacuum pressure however and the screws are both at about one full turn. I’m not sure why when all the way in the vacuum doesn’t fall away.

[@MuscleCarSolutions]

Your throttle blades are open too far and the transfer slot is exposed. Turn the idle speed screw all the way out until it does not contact the throttle cam. Set your idle mixture screws to two turns out. Attempt to start the engine while turning the idle speed screw in slightly until it idles. In park (if you’re an auto) it should be around 1000 rpm or less.

[@asslowshop396]

I appreciate it. 351 isn’t running like crap anymore

[@Ty2Tymes14]

I have a 350 sbc i cleaned the carburetor while running with carburetor spray and it shut off now it won’t stay running any suggestions?