Carb Idle Mixture Screw - How To Adjust Properly (EXPLAINED/DEMONSTRATED)
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- Опубликовано: 8 сен 2024
- this is for you ERIC WUEBKER - how to adjust idle mix screws on your carburetor properly (since i have never done this on a running engine on camera) holley carb idle
Back in the day, me and my brother would do tune-ups all the time with all of our cars and for relatives and friends and we still do it with our 65 Impala. Takes a little time, but overall its easy and a nice small project to do on a lazy weekend. Takes about half an hour including the time for the engine to warm up. Tach/Dwell meter, vacuum gauge, timing light, distributor wrench, small screwdriver, and an allen wrench are all you need. Same technique applies to all makes and models, four, six, or eight cylinders. Standard engines with hydraulic lifters would go well over 20 inches of vacuum with a proper tune. Be sure to kill the vacuum advance and plug the port on the carb while setting the timing, the rest of the tune-up can be done with the advance hooked back up again. Automatic transmission and by yourself? Do the whole tune-up in Park, throw it in Drive, look at your idle on the tach, back in Park, then keep doing that until you have correct idle speed. Most old style V-8's go about 600 RPM while in Drive. You'd be amazed at the difference once you're finished. Its rewarding and lots of fun too.
Hi i have a quadrajet carby whats the best way to do the mixture i just brought a vacuum gauge any help appreciated
@@Farmer2492 ruclips.net/video/Nbih0zm_Ldw/видео.html
@@troydzuricsko7331 Thank you very much
Great presentation! I remember doing this back when cars were not completed computer controlled robots😁
Finally I see someone who knows enough to go slightly rich by turning the mixture screws out a quarter turn. No one else on RUclips knew this. That allows you to go longer until you need to adjust the screws again. If you leave the screws at their highest vacuum, highest idle speed setting just the slightest bit of contaminants in the idle circuits will cause a poor idle. Better to be a little rich. You people out there should pay attention to this video. It is the only one that is right.
Everyone knows you go a quarter of a turn.
@@d711van1 i didn't. Thats went im here
I’m looking for help adjusting 6 pack carbs. Is that a similar process compared to this?
If you cannot get to mixture screws with air cleaner on, what would you do? best video I've found explaining how to!
Hey really like it when you and Kevin work together. I live in Hungary as a Missionary and I really like what you guys are doing. Thank you for doing these things for older American like myself. Keep seeking your dreams.
Hi brother, I want to thank you for all your help you only one goes into Details most of us forget or didn't know, timing and fine tuning is a lost Art as Fuel injection has become most common well old school 55 years old won't find no electronics in my v8 S10 we owe you Sir
one of the best videos I've seen . thanks
Good info pretty much what I do!
Off the subject a little , on some of these dual plane carbs have you ever cut the divider wall of the intake about a 1/2” maybe 3-4” long?( just under the carb or at the base of the carb mount)
Normally I’ll run a 1/2” phenolic spacer but in some cases hood clearance is an issue….so I cut down that divider wall and helps a bunch with signal balancing and intake pulse! Makes a noticeable difference in low end torque .
You know what you thought you said. I wish I knew what you were thinking. What are the 2 screws you are talking about. You sound as they are both for fuel. I thought 1 was for air. I then than not knowing what you are turning, good video.
Learning alot from your videos where do you hook up a afr to
Love all your videos very informative. I’m just to the west of you in eastern South Dakota.
I just to the west of you in Central South Dakota
@@UnyieldingSeraph im just to the north of you in north central South Dakota!!
HEY Luke, i cant wait to get my truck sounding and looking like your engine bay.
that being said, it might be helpful to actually say wether enriching or leaning is turn out or turn in.
same for timing. advance or retard means nothing to a newbie unless you also say CCw or CW.
i just picked up a 76 F150 looks prettier than it runs though... .
Seemed to run decent at speed but large stumble off idle.
Accel pump seems to squirt both barrels, is set to out lever spot and top cam spot.
Doesnt seem to be any power valve leaks
Shaft seems a little loose but i dont know how loose causes vac leak?
then replaced cracked brake booster line, idle/stumble got worse.
Checked fuel filter, it was FULL of large grain rust.
replaced filter at carb and another see thru one before pump for visual reference.
then reset the mixture screws from about 3 turns out to1.5, wouldnt even start, barely fire.
SO i unplugged all vacum hoses and plugged them with multi sized plug kit.
IT fired right up, but still has off idle stumble.
Then i advanced, turned distr CW and idle picked up.
Stumble is a little better
Im thinking carb needs to be opened completely up and check for sediment and blow out all orfices and replace wear parts.
What do you Ford/Carb experts think?
which of those carb vac hoses need to be hooked back up?
right now ive only got brake booster, w/o which i have about 10% brakes and also the vac advance to dist. all others are still blocked off.
not even sure what that thing behind the carb is hooked to vac lines?
Wow very informative video thanks for sharing man
I have a single barrel carb i would like to know standing from the tail pipe my fuel mixture screw is in the center at the back of the carburetor so standing from the tail pipe which way must i go inorder to lean the mixture out beacuse when i turn the screw all the way in the car cuts off and when i turn it abut 2 turns anticlock wise then the car starts
Thanks for sharing 👍
Would be good to know what direction you were turning the screws to lean it out and which way makes it rich.
In is lean out is rich
Hello, your videos are awesome..Hope you could answer 2 questions for me on timing and carb 1) My 1966 Mustang 289 seems to like pretty high timing - 12 to 15 degrees which is much higher than FACTORY spec. Does that mean something is wrong? 2) I have an Edelbrock carb and manifold, did the steps you outlined. What is the BAD you mention (as have others) if you make it too lean (like if I left it at max manifold vacuum)? Damage? Poor performance? Thanks !!!! Keep em coming
12-15 degrees is fine as long as it doesn't ping. Nothing bad will happen if you adjust idle mixture to max vacuum. That is the ideal setting but in reality is difficult to achieve precisely without an AFR meter and, with a carburetor, even then. Once you find the best lean setting turning the mixture screws and extra 1/8 turn or so rich reduces the possibility of stalling and rough idle under less than ideal conditions such as being stuck in traffic on a hot day. Engines can tolerate an overly rich idle mixture much better than a lean one.
@@65sohc Thanks !! In final settings, Its actually about 18 degrees for best run and that also gives about 32 degrees total advance. I am also told this is not unusual so ...I go with it :-) Again thanks
@@arcorob Is that 18 degrees initial with vacuum advance connected? Because if it is w/o vacuum advance in play (the correct way to set initial timing) that means your distributor is only supplying 14 degrees of centrifugal advance which is unusually low.
@@65sohc Vacuum advance disconnected and carb
port capped to test ...been trying to figure ..why so high..and as you say full advance kinda low ...if I drop it (initial at 10 or 12) a vacuum gauge on the carb port tells me not enough advance ..if I set for about 15-16 I only hit about 30 on advance...It has a pertronix unit but could my distributor or advance unit be bad ? I am REALLY tempted to do a distributor change but not up for the challenge yet. but could be..Thoughts?
@@arcorob Pertronix distributor or just Pertronix points to electronic conversion of stock distributor? If it is Pertronix distributor the amount of centrifugal advance is easily adjusted.
Ford F100, 360, 4 barrel, Automatic. What is the procedure with an automatic transmission? Would you do this with the transmission in drive as that is how the idle is supposed to be set with an AT? Or would you set the idle in drive and then perform the vacuum adjustment with it in park? Thanks in advance. I have followed your channel for awhile and enjoy it very much. Your videos are well done and thorough. I can also appreciate how the video production has evolved over the years. Well done sir.
Hey, thanks so much. I really fail at mentioning to do autos in drive with either a friend on the brake, or the parking brake on (a little risky) 👍
What do I have to do to get my vacuum steady, thanks.
Good info, I enjoy watching your vids thanks, Did you ever try using color tune plug ?
Screw in to richen or out?
Screw out
Are you adjusting this idle with the vacuum advance or without vacuum advance?
What is the vacuum number I’m looking for
Thanks for the video
running a very quick cam with 102 lobe degrees, it wont hold an idle under about 1200. I had to drill the plates on an HP holley.....all in a boxed frame 71 vega.....truck sounds nice though!!
chevy vega I’d imagine so, that’s a heck of an LSA! I believe this cam was around 108 or 110 - I’d have to look at the old card!
cheers well explained
I have an automatic , does the car have to be in gear? Or in park?
Does most of the same stuff apply for a 6 cylinder 1 bbl?
hi 289 question I adjusted the carb but when I'm in drive it spiders a bit what.wouls u recommend
To go rich in the mixture, do you turn the idle/mixture screws clockwise or counterclockwise?
Counterclockwise
It’s confusing if you have worked with tractors since often turning them in is richer
@@ThunderHead289 would that apply to all carbs? I have a Rochester 2GC on my Pontiac 400.
What about the mixture screws in the back. You don't turn those?
If you have them, they need to be adjusted as well. All evenly at the same time and the throttle blades should be open the same. This carb here just isn't a 4 corner idle screw system
So each of the screws should be the exact turns?
Is a vacuum gauge the same as a fuel pressure gauge?
It is different in the sense that fuel is pressure while vacuum is a suction effect! So unless they are set up to accommodate both, most are specific to one or the other
Dakota if you don't know much , stay away . answer not even close
How about if it’s not a Holley carburetor is it the same way you explained it?
Little late but yes!
Trying this asap
How do I ajust a eldubrok 4 barrel I have no sound for some reason so I can't hear them
I've got a 70 mustang with a 351 W. motor has been rebuilt and know I'm using a 600 cfm edelbrock. can you do a vid on adjust this thing. It's driving me nuts
I have a 600 CFM Edelbrock as well. Edelbrocks don't like fuel pressure over 6 pds. Once you have the correct fuel pressure it is easier to adjust. I put a regulator on the fender well and permanently attached a 1 1/2 inch fuel pressure gauge on one of the two outlets of the regulator as I am not running a return.
If I remember right the ideal mixture is 14.7 : 1 for gasoline engines in you got a digital air fuel guage.
+TRUNKBACK JIM it is, that is indeed stoichiometric ratio for gasoline BUT on a carbed engine, you will have fuel and air density variation with humidity and temp change, so 13.5 target is much more reasonable and forgiving. fuel injection is a different story.
ThunderHead289 We certainly get some temperature and humidity change in Iowa for sure. Thanks for sharing.
we sure do, we finally got some warm weather here where we can do something this weekend. what part of ioway?
ThunderHead289 In Des Moines, I worked at Whitlock and Jockos Auto Parts stores here in town if your old enough to remember either of those. Whitlock has been gone for 20 years but most people remember Jockos before it sold to carquest.
+TRUNKBACK JIM my mother worked there some 30 years ago. I'm up in ames
Can you tell me why my 68 mustang stock 289 making a little popping sound from driver side? Has new plugs and wires two years old? No nose from vale cover.
exhaust leak maybe
It’s lean. Fatten it up
Awesome!...Thanks!
I have a 72 with a 360 2bbl and when ever I take the choke off it stumbles and dies. Motor is up to temp.
sounds too lean. 2bbl? may need to upgrade to a 4
Thanks
Has someone already said that I didn’t know Ray Romano fixed trucks?
Hey I have a Holley 750 cfm on a 400 sbc. I don't have a vac gauge to test anything but I'm working on getting one. My problem is that I have no idle. I drove the car on the highway for an hour until it started surging and stalling but I managed to get it home. I have to set my distributor at full advance just to get the engine to crank up. My carburetor backfires now ( like a cannon going off) but I tried turning the distributor clockwise and never turns over but if I set it fully counterclockwise it fires up and backfires.
I managed to get it running lately but only for 3 minutes then it dies. It starts with a very high idle around 3000-4000 rpm and just stays there surging up and down until it dies. Oh yeah that's with the idle mixture screw back completely off.
Some people tell that I should try to keep it idle at 5000 rpm to set everything but I'm nervous about the backfire.
on the chevy with the distributor in the back, i believe you turn it counter clockwise to advance the timing. nevertheless, dont idle it that high. you will have to get a timing light on it since such a small turn will change the timing significantly. do this, get your distributor to about 8 degrees of timing at top dead center, then pull your carb and flip it over so you can see the transfer slots (long thin cut line in the carb bores) set your throttle plates so that there is only a square showing. then turn your carb screws all the way in and set them to one and a half turns out. this should get you where you need to be and you can fine tune from there.
Kendricks Hayes Jr It sounds like your distributor is 180 out, have you taken it out lately? You may need to put the motor TDC and drop it in
Kendricks Hayes Jr
Do not listen to this guy Thunder Head, eH sounds like he was dropped on his dunder head, speak simple. every fucking chevy big block and small block V8 is the same ,stand in front of engine. rotate your vac advance toward you that,s advance, turn it away from you thats retart like a lot of folks here.
Amber Chrismen please tell us more so we know!!!
Hey guys I put a 750 dp on my big block rl Camino buy my mate at his carb shop and it stinks fuelled out of the pipes
Chevy 350, edelbrock carb, just bought a vacuum gage and I thought I was supposed to hook it up to the port in front of the carb? There’s two, one going to the vacuum advance and the other plugged up. I do have a port behind the carb on the intake. Which one is best? Then, I was told to turn one screw in, then back out to see when it gets to the highest point. Then the other screw.....Please help, thanks
Whoever told you that is wrong - follow the video as I have presented it.
Also, any port that at idle is sucking air in is a good one to hook your gauge to 👍
thank you
So your adjusting all 4 screws correct?
Many carbs only have 2. If you have 4, adjust 4. All evenly
can you send me a link for both?
Wait you need your air filter on while testing?
Junk Cars - This is not "testing" it's setting as such the closer the conditions are to the real world use the better the results. ;-)
i have a 1973 f250 with a 2bbl stock carburetor, im looking to getting it looked at weather it needs to be replaced or not. It probably hasnt been tuned in years. Should i just try and tune it and see if it helps? the truck starts idling rough when i come to a stop at a light, and occasionally when i go into reverse. Also, i want to try and stay stock for now, can i just stick with the 2bbl, tune it, and get new headers and new exhaust? im going with the flowmaster super 44, will that boost performance and make a difference just until i switch to a 4bbl set up in the summer time?
I'd try and adjust it, I have a lot of carb videos discussing how to tune. I'd have a better idea before you jump into adjusting it
ThunderHead289 so try and tune the carb first before I think about replacing?
+mike anderson I definitely would, though a 4 barrel is better all around. If you do go to a 4 - get yourself a summit 600.
Do those adapters work at all for 2 to a 4? Or do I have to do the manifold too
+mike anderson you have to do a manifold.
Told us no info on which way leans and which way makes it richer
I realize this video is 3 years old but I felt compelled to comment anyway. Get rid of that POS miniature air filter! You've got long tubes on it so one can assume you want it to breathe efficiently but that certainly can't happen with that filter smothering the carburetor.
What happens if the idle mix screws were screwed in and seated and not turned out ....what would happen.Is turned all the way in max lean?
If your screws are all the way in and it still runs, it means you have too much transfer slot exposed on your carb ie your throttle percentage at idle is too high
I love EFI. 😂
sounds like you need a lot more idle, thought it was going to die at the end . either by drilling a 1/8 inch hole in each butterfly of the mains or turning the idle screw
chevy vega that’s what she sounded like idleing at a steady 900. Solid lifter cam engine
And if your running a open breather and a pvc your just sucking through that open filter breather think about it ...
the grinch what are you referencing?
That air cleaner is way too small and restrictive; great video though !!
Oh it’s horrible at any hard throttle - idk if I showed it in this video, but that’s what under hillborne scoops.
Funny how putting one of those on anything makes folks think you have some crazy insane engine - when in reality they are like breathing through a straw
I think if you did a more hands on adjustment explanation, you wouldn't get so many questions.
Come to my place and tune my truck Please lol
When you say enrichen, is that clock or counter clockwise?
In is lean, out is rich
IN as in towards the rear of the vehicle? out as in away from the vehicle?(forward?)
in as in turning the screw in (clockwise/righty tighty)
What if my idle is COMPLETELY fucked over and I need to restart the whole tune from scratch? There’s nothing on the whole entire internet on what to do about it
Wrong - watch my carb tuning 101 videos 👍
Welcome to the house of carburetors
ThunderHead289 Thanks brother man, I was really frustrated earlier sorry about that
I hooked up a gauge and getting 15 to 16 vacuum .idles at best after less than 1 turn .but idle is not perfectly smooth I had tan color spark plugs after this set up .if I turn it more than 1 turn I got black plugs .vacuum gauge does not really go down though it's hard to find that sweet spot any ideas?
how much do you have your transfer slots exposed?
+ThunderHead289 good question let me find it out
+casanovaevren it was exposed too much I set the screw all the way up its still like 2 square slot now but before throttle was crack open.I set the mixture to the best idle then drove it I got back fire on the carb which was too lean then I set them up 90 degrees out and started to smell a nice burn but not too heavyand not burning my eyes like it did before it runs better idle is not perfectly smooth but I can live with that just got the car 79 Corvette with a mild cam 12 initial 34 total timing and waiting for some appropriate vacuum advance to hook up currently I maybe get 6 or 7 mpg
sounds like you are getting fairy close! the bigger the cam, the more precise you will have to be with everything. it may just be your idle speed, i have to idle at 900 for a clean running idle with no load up.
+ThunderHead289 at 900 it's smooth I ll see how it ll be when I hook up vacuum advance thanks for the video
Ekkkk teflon tape on a holley. Run run away
Si
Very confusing! Which way richens? Which leans? You started at 2.5 turns out...where did you end up? 1.5? At the beginning is seemed that two vacuum gauges were optional, by the end they both were needed. You are assuming way too much knowledge on the part of the inexperienced viewer. A common RUclips foible...
This is a really old video of mine - as I got older my presentation skills dramatically improved - here’s an exponentially better walkthrough:
ruclips.net/video/bUv5tUC6Ioo/видео.html
@@ThunderHead289 Hey, thanks. I didn't mean to be unnecessarily critical just constructive. I have watched some of your other video's and gained useful information from them. All in all I'm glad you take the time to do these. I'm finding that there are very few people that have carburetor knowledge!
Hi brother, I want to thank you for all your help you only one goes into Details most of us forget or didn't know, timing and fine tuning is a lost Art as Fuel injection has become most common well old school 55 years old won't find no electronics in my v8 S10 we owe you Sir