Holley Idle Mixture Screws Too Far Out

Holley Idle Mixture Screws Too Far Out2) The idle speed screw is ALL THE WAY OUT. The mixture screws were out 1 turn in the front and a 1/2 turn in the back to give 13" vacuum at idle, the timing is at 30 deg total all in at 3000rpm with the vac advance disconected, i just measured the exposed transfer slot and it's at. Problem setting idle mixture. Manifold vacuum is 17-18" remember the emissions 6919 has fixed fuel metering for idle and the screws control the airit's backwards from most Holleys. So the first thing to check is the transfer slots visible under the throttle at idle are in the range of. If you are 2 turns out on the ctr carb idle mixture screws and the idle is still too lean - the outboards need to contribute more fuel to the idle. Make sure the timing is set and the engine warmed and up to operating temp, set the mixture idle mixture screws by tapping on the accelerator pump to give the engine a quick shot of fuel, but without cracking the throttle open. For a closer look, check out the following. cudavert DARTAHOLIC Joined Apr 16, 2009 Messages 2,819 Reaction score 449 Location Hesperia, CA Apr 24, 2010 #8 What is your idle speed?. ) Then back off (turn counter-clockwise) each screw so that each is at the . We've found that sneaking up on the adjustment with very small steps toward the final adjustment is beneficial. 5 turns, vacuum is around 8 inHg and the engine seems to like it, but the fuel mix is very rich and smokes even worse at idle. Shop for Holley Idle Mixture Screw 2 Piece with confidence at AutoZone. The primary's are 1 1/2 open from seated & the secondary's are 1/2 from seated. So you can back down on the "idle speed" screw to lower the RPMs. Repeat this process for all of the idle mixture. If you have a hard time getting it to idle, adjust the curb idle speed screw clockwise so that the engine doesn't shut off. The idle screw adjusts the airflow going into the throttle body and at the same time pulls fuel from the float bowl through some very small channels. Make sure the engine is idling at around the normal curb idle speed. and again here And if the needles screw all the way in, check that your transfer slots are setup properly. The vacuum gauge I am using is an Innova 3620 - https://amzn. However, if done wrong, you’ll wind up with stalling, pinging, and a rough idle. Adjust the both screws a small amount each time, i. Last edited by PaceFever79; 03-11-2009 at 05:40 PM. If you only need half a turn to supply the correct idle mixture the circuit is fuel heavy. This was done on the other side and when the screw was turned in too far it started to run rough and then stalled the 289. The previous owner apparently removed the lead plugs and I'm not sure what happened to the screws. This is caused by the plates being too far open at idle, idle speed too high, late intake valve closing events, and timing being way off beam at . That cam will want a LOT of initial timing like 16-18 degrees. If you screw them all the way in and it's still running, your pulling fuel from somewhere. HOW TO SET HOLLEY IDLE MIXTURE AND IDLE SPEED | Holley Carb Secrets | Holley CarburetorAfter A long while I have put the most cohesive method of setting up t. THEN BACK OUT THE NUMBER OFTURNS RECORDED ON DISASSEMBLY. (Turning in the screw too tightly will damage the needle valve and/or its seat. If you are driving it you should be able to tell if the rest of the carb is functioning properly. Holley Idle screw (Or any carb) not being responsive is due to; Overly rich condition Advanced timing Throttle paltes open to far - look into carb primaries with engine off, you should see a square. Back each idle mixture screw out 1/8 of a turn and do it again until you have a nice clean, even engine performance with no surging when she is cruising with your foot just lightly on the throttle. Turning the idle mixture screws clockwise (in) leans the idle mixture. When driving to the office, yesterday, listening to The DirectGov ads, and looking at the posters while in traffic jams, it occurred to me that Learn about Insider Help Member Preferences When driving to the office, yesterday, listening. Everything can be accomplished at home, with (extremely) simple hand tools. Recheck the idle mixture needle position then tighten the hold down clamp. Holley Idle Mixture Screws. Switching to ported vacuum, I lost 3 inHg of vacuum, but now the highest reading is achieved with the idle mix screws at 3/4 of a turn out, instead of seated all the way. com/support/carburetor/ Tips on adjusting the idle mixture on Holley carburetors, using a simple vacuum gauge . At 2 1/2 turns I think you are fine. My 427FE Is Going My 65 Fastback! a70eliminator 2,405 11. When I fatten the mixture back out to 1 or 1. Again the point is if the throttle blades are open too far and the transfer slot is completely uncovered you are not on the idle circuit. Were assuming this is a cam problem. Idle Mixture Screws and Gaskets Holley 26-110-10 Part Number: 510-26-110-10 Holley Idle Mixture Screw Gaskets Cork Idle Mixture Screw Gaskets Cork 10/pkg View Details $15. Manifold vacuum is 17-18" remember the emissions 6919 has fixed fuel metering for idle and the screws control the airit's backwards from most Holleyseven the screws are different. This increases fuel flow making the. Now that I have it running again, the carb is. Try it with all 4 about 3/4 turn out. 031 squirter on it Measure the diameter of the hole the mixture screws seat into when all the way in too. UPC: : 090127418758, such as an unprinted box or plastic bag, See the seller's listing for full details, undamaged item in its original packaging. I'm trying to keep from drilling holes. Get a secondary on top of the base screw adjustment thing from Holley (see below). Turning them in all the way still does not kill the motor, but I do loose vacuum and the idle becomes less stable, so I'm headed in the right direction. Just finish retuning my Holley 4150 HP carb and the Idle mixture two on the idle air bleeds so the mixture screws can be adjusted out?. Just finished putting the intake manifold and everything back on after replacing a few gaskets. When we turn the idle mixture screws, they do nothing, we run the car with both of them turned in, and it doenst even shut off. by nzlwayno » Fri Mar 13, 2015 6:29 am. Most stock motors should idle around 16~18 in/hg. Open each side 1 full turn from the dead stop. If they are too far open at idle, then transfer slot happily supplies all the fuel the engine needs to idle. Now back the screw out until the specified rpm is achieved. One thing , make sure all of the holes intersect in the idle circuit , Take the mixture screws out and shoot carb cleaner through them Make sure the fuel level is right in the bowls ,, i like the orange cam usually and try a. If one side is very open, it can easily run the entire motor at idle. An engine that is idling too high may be caused by a faulty idle air control motor valve that has completely failed or that has simp. and it didn't resemble the typical 4150/4160 Holley carb in any way,. These are the idle mixture adjustment screws (yellow circles). If you turn your idle mixture screws in all the way and the motor doesn't die you most likely have a blown power valve. First of all the carb is the original one but it is not new. After a rebuild of the old QuadraJet and dealing with various starting & running issues last year, I decided to replace it with a new Holley Marine spread-bore. So this is a custom made carb made by Holley for Ford. Then start the car (it will probably be idling very high now) Then turn the secondary stop out until the idle starts to come down to the desired level. If you have the plates too far open you may be pulling fuel from the idol circuit and this will cause the mixture screw to be unresponsive. Adjust throttle screw till it reaches about 6-700 rpms and work the mixture screws till a smooth idle. Vacuum gauge attached to the intake manifold The primary metering block is usually located closest to the front of the engine. If you want to start from scratch, make sure the screws are lightly seated when you turn them in. Is it out of the ordinary to stumble the engine at anything less than 2 turns out? My best idle seems to be about 2-1/2 turns out, . leaning out a Holley HP at idle. Pay attention to their position and back them out two full turns. The idle metering adjustment screws (arrow 2) are located on the primary metering block on most Holley carburetors. 070 drill bit or open the secondary throttle plates some. There are several ways of doing this depending upon what tools you have available to you. You need to adjust each idle screw evenly when the motor is running, not leave one closed and the other open 2 turns etc. then adjust the idle mixture needles for best manifold vacuum. SLOWLY AND GENTLY turn each screw in (clockwise) until it is seated. If I leave it and go to the other side I can finally get the motor to start to die w/ 1/2-1 turn in (set at 1 1/2 out). If it won't run with your idle mixture screws at 2 turns out, throttle plates adjusted properly, and CHOKE OFF. Based on that I have seen some article where it is mention to do following step: - with engine off. Too hard and you will damage the screw. Holley Idle Air / Fuel Mixture Screws Brass With Cork Gaskets. Answer: Original Question: "How do you adjust the idle mixture screws on a Holley carburetor?" NOTE: THERE ARE NO "SENSiTIVE IMAGES" (NONE, ZERO, ZILCH) IN THIS ANSWER. Ratpowered look at the ends of the mixture screws and make sure the tips are not damaged then you might try this before you open the carb up,remove the idle mixture screw put your air nozzle up to the hole then block the air bleed and give it a few blast with the 30-35psi, keep your face away from the carb. While turning in the passenger side screw it went all the way in and didn't stall the engine. From this point you can lean it by clockwise turns, or rich by counterclockwise. Setting-up Holley's is really pretty easy. It's advertised as the direct replacement for this. Carburetors - Holley, unresponsive idle mixture screws! You have the throttle blades opened way too far just to maintain a 900RPM idle . 1/4 Turn each in or out as required. Next, back them out 1 full turn and restart the engine making sure the choke is. Turn them slowly clockwise and counter-clockwise until the vacuum gauge reads the highest possible reading you can achieve. either the throttle is open too far exposing too much of the transfer slots or the power valve is blown leaking fuel into the manifold. getting the idle mixture correct. Take turns with each idle mixture screw. There is a measurement but I can not remember what it is. Adjust all four idle mixture screws the same amount to get to the target A/F. ENGINE AT OPERATING TEMPERATURE REFER TO ENGINE . Same as above, your idle mixture screws should be able to shut down your engine. A clogged vent tube would push unwanted fuel out during idle. If you add a degree, so 16 initial, and 36 all in, it may help stabilize idle. Your idle may be fine now, it won't when you are allowing more air into your engine ! What is happening is that you have too much of your idle transfer slot exposed so your mixture. If you can get some pressure through these channels they might clear out-assuming that's the problem. This quick walk-through will get your Holley carb up. This will "advance" the timing by about 7 degrees at idle. If I turn one side of the idle mixture screw all the way in, nothing happens. Your mixture screws should be near 1 1/2 turns out. Is there a such thing as too far in or too far out if the the screws are If the holley carb idle screws need to be 3-1/2 turns out from . Open the idle mixture screws on the. This is usually 1 and ½ to 2 turns counter clockwise. idle mixture screw doesn't work. Holley Idle Screws Set At 3/4 Turns. Idle mixture screws have no response. Listen to the idling of the engine and stop turning the screw when the engine's idle sound starts sounding irregular, like it is revving too fast. If done right you’ll have a perfectly smooth idle. Get yours online today and pick up in store. However, there's always the Holley idle mixture screw location. Turn the screw counterclockwise and clockwise 1/2 a turn from the middle position and listen to the sound of the idle. - Start then engine and adjust idle speed. This is why your idle mixture screws are having little affect. If it doesn't stall, then you know your throttle's open too far at idle, and you're pulling fuel from the. There are a couple of ways to adjust the idle mixture. Start turning the 4 idle mixture screws in or out 1/4 turn at a time ( whichever way necessary in order to achieve most vacuum or most rpm or highest rev by ear. 040 then your running off the transfer slot and not the idle discharge port and that will make the idle mixture screws unresponsive and give you that problem. With the "idle speed" screw now let out more. I have a 1988 Chaparral boat with a 5. If you get the gasket between the carb and the spacer flipped on a 2100 you will get a big vacuum leak, look there too. The application is a street/strip F100, shortbed, C6, 3:50 gears. Each side should have the near the same amount of turns. Holley Carburetor: Idle and Transition Circuit Calibration Guide. Carb is a Holley 4779-7, datecoded 2464. Idle Mixture Screws All The Way In. The other possibility is that an air bleed is plugged up. bumping it up that might speed up the idle allowing you to close up the throttle and get the idle adjustment back. Run the engine, and adjust from there. If the holley carb idle screws need to be 3-1/2 turns out from seated, to get the best idle, I'd be looking for a carb or manifold vacuum leak. If you are not in the holley specs with mixture and/or idle stop screws adjust the secondary stop so they are. Try that and let us know what happened. I double checked the timing and found it was still at the 8 degrees BTDC, that I had it at previously. You should be able to kill the motor at idle by seating the idle mixture screw. 4) Ported vacuum and manifold vacuum ports are closed off. as far as the screws, with the engine off turn both screws clockwise until they are all the way in. idle mixture screws not working. Idle throttle opening screw is opened only slightly and it's a stock motor, so I doubt if the throttle blades are open too far. To put it another way if you get the combination of idle fuel restriction and air bleed right for proper transfer mixture you usually need to open up the discharge area with the idle screws to 1. After I fixed the carb, it too would idle the fastest with the mixture screws all the way in. This being the case, you can't purchase "official" idle mixture screws. the first thing that comes to mind if your idle is high enough and you have too much of the primary transfer slot exposed beyond about. How to Adjust an Air Fuel Mixture Screw: 7 Steps (with Pictures). 7's w/ Closed Cooling Volvo Penta DuoProp Drives Kohler 4 CZ Gen Set Please, no PMs. Holley Idle Mixture Screw Gaskets Cork. Turn each screw in 1/4 of a turn and wait for a second for the vacuum meter to catch up. As the throttle opens and more of the slot becomes fuel feed and the slot’s bleed function diminishes, the small upper bleed then causes richness. Includes Cork Factory Style Seals. also at times you can have a power valve that is good …. Short for Interface Definition Language or, alternatively, Interface Description Language, a computer language or syntax used to describe object Short for Interface Definition Language or, alternatively, Interface Description Language, a co. Make sure they are free flowing. I have a holley 570 Street Avenger. Once installed you can adjust it until it will pull the advance in at idle,then reset the carb with 2 turns out from closed on the secondary throttle blade and squaring up the primary transfer slot, along with setting the mixture screws at 2 turns out. When I adjust the idle mixture screws to highest vacuum, 21 inches in park & 19 in gear and smooth clean idle, I'm at 10. Adjust all four idle mixture screws the same amount to get to. The adjustment procedure is simple, slowly close the mixture screws until the engine faulters (too lean) and then back it out to where it runs well and perhaps a smidge more. Holley 6919: One Idle Mixture Screw Has No Effect. Idle Mixture Screws Inoperative. They have no effect on the mixture once you hit the gas pedal. My Spelling is not incorrectit is creative R. Now, with the primary idle mixture. Starting adjusting your mixture screws 1/8 of a turn at time clockwise. Once they're properly set if the idle RPM is higher than desired, loosen the hold down clamp and turn the distributor slightly to achieve the desired idle RPM. All the usual suspects have been mentioned - power valve or gasket (lot of problems here as the gaskets don't seem to seal well anymore), metering block gasket seeping or idle transfer slots too far exposed. Holley 4779 750 Double Pumper Fuel Mixture Problems – Rich Idle. The idle mixture screws should be more responsive now. This to a huge extent negates the need for the secondary idle circuit being there at all. Parts are just part of what we do. I was troubleshooting a hard starting condition on one of my Ford 351W engines yesterday, and found that the mix. Holley's products include carburetors, fuel pumps, fuel injection, intake manifolds, and much more. PB The two screws y'all are trying to adjust are the IDLE mixture screws. It sometimes will lope & die, and sometimes idles too high. If the idle speed is too high and the front idle speed screw completely backed off, you have gone too far. Make adjustments 1/2 a turn in either direction to find the smoothest idle speed. What Causes High Idle Problems?. Why do i have to turn in the idle mixture screws so much to lean it out and get the best vacuum reading? Is the carb jetting to big to cause these types of issues? This is a Pro System reworked 850 Holley DP and this carb was setup for a Victor Jr intake but now i changed to a Chevy Factory ZL-1 intake and i do have a Factory ZL-1 4296 Factory. And lucky me, both of my idle mixture screws are missing. You will be shooting for the highest vacuum reading. The clue is that when the idle screws don't kill the motor, it's getting fuel from somewhere. After the engine has warmed up, you can adjust the idle screws to get the smoothest idle or highest manifold vacuum reading. Holley 735 428cj factory carb, float levels are just at the bottom threads. Turning the screw IN will cause the engine to run richer with the inverse idle circuit, as the screw is reducing the amount of idle air. Initial idle mixture screw setting started at 1 1/2 turns out You have about 4" less vacuum, and the idle is too high when in gear. So the first thing to check is the transfer slots visible under the throttle at. Turn the screws all the way in until lightly seated. Both idle screws should be the exact same number of turns out at all times. If it doesn't stall, then you know your throttle's open too far at idle, and you're pulling fuel from the transfer slots. If the engine doesn't respond to turning the idle mixture screws, there's a good chance you're running too high of a power valve value and the power valve is opening prematurely. 040 then your running off the transfer slot and not the idle discharge port and that will. Tuning Your Holley Carburetor Made Easy. Some carburetors have a reverse idle adjustment (some 2300, 4150 and 4160 Holley carbs, for example). Also as soon as you open the throttle the idle circuit stops working and the main circuit takes over. 70 (2) Estimated to ship direct from manufacturer on 09/29/22, pending manufacturer availability. 3) Both idle mixture screws are 1/2 turn out. Idle Mixture Screws – Adjustment and How to Purchase. The number one cause for high idle is an imbalance in air pressure. Turning the idle mixture screws clockwise (in) leans the . Anyhow, if idle is too low, open the secondary plate a tiny bit to get the idle up. 5 turns in order to get enough idle fuel RAIDER SS. Even closing two are unlikely to stall the engine. to/3eg4T5j (affiliate) The carb is a Holley 80457 - https://amzn. Your mixture screws should be . for reference and a look at the original, traditional (clockwise = lean, counterclockwise = rich, idle mixture screws) circuits within holley modular 2/3/4 barrel carburetors since approximately 1957, that work with fully and solidly established (roughly 100 years ago) efficient and powerful internal combustion physics, where air:fuel ratios …. Start by turning one of the idle mixture screws on the primary metering block clockwise until it bottoms out. All the usual suspects have been mentioned - power valve or gasket (lot of. In gear depends but sounds like you're in the ball park. It runs better at 3/4 turns on the idle screws, but the carburetor runs rich (i. Poke the air bleed with a guitar string, shoot a little carb cleaner in there, open the idle screw wide open and blow it through with an air compressor. Now maybe I've got this backwards, but if your idle timing is too far adavanced, you. You must do both screws equal number of turns. drill the throttle plates with a. First run the screws in all the way until they seat, lightly. NEVER screw the idle mixture screws in all the way and too tightly. It has a Holley 4180c carburetor LIST 50260-8. Need some direction to figure out why idle mixture screws do not respond. The carb is a 870 Street Avenger. 7L Mercruiser (Marine Chevy 350). No if three idle screws are feeding fuel the engine is unlikely to stall. Squirting starting fluid at the base of the front of the carb causes idle to blip a little bit. We’ve found that sneaking up on the adjustment with very small steps toward the final adjustment is beneficial. the cam is a comp cams 280H, 280 duration, and. I back them out each one additional turn, and this smoothed out the idle quite a bit, and it was still idling slow, but just fast enough to keep running. First thing is check the float levels. Note that once the throttle valve is opened sufficiently to run from the main metering circuit, the idle circuit is disabled, so these screws would have no effect on the main circuit. At some point, I pulled the PCV valve out of the VC and the engine died. Could be a huge vacuum leak or clogged idle passages, wrong gaskets, dirty carb, etc etc. The simplest, but least precise, me. Tech Tip: How To Tune Holley Carburetors. The inverse idle circuit may readily be identified by the reaction of the engine to a change in the adjustment of the idle mixture screw. Turning the idle mixture screws counter clockwise (out) richens the mixture. General rule of thumb adjust to best smooth idle then lean out 1/4 of a turn. We're using a very common vacuum secondary 3310 Holley along with a 4781 double pumper as the examples (and everything shown here applies to factory installed Holleys too). The basic idle setup of a Holley isn't difficult. The idle mixture screws seem not to work at all, as the engine doesn't stall when they are screwed all the way in. (aka RicardoMarine) Gresham, Oregon 2850 Bounty Sedan Flybridge model Twin 280 HP 5. The idle issue is more one of getting air which is why your carb has the drillings in the primary throttles. The first thing that comes to mind if your idle is high enough and you have too much of the primary transfer slot exposed beyond about. I think this is because these mixtures screws are essentially a controlled vacuum leak and backing them out reduces the leak which increases vacuum, but leans out the mixture too much. Set the screw in the position where the engine's idle sounds most even and smooth to balance the fuel mixture. While at idle, back them out 1/8 turn at a time, alternating between the 2 or 4, until highest vacuum is achieved. 080" and i noticed that the timed vacuum port is starting to get uncovered. Turn each screw out a bit for a start (maybe 1 turn). Now in small intervals and evenly, turn out the mixture screws. If you want to start from scratch,. To change this, you have to re-jet the carb. My 383 with a 670 has the idle mixture screws set under 3/4 turn and most Holley carbs I've tuned on SBC's end up around 3/4 turn and no more than a full turn but I always start at 1 1/2 turns out for a base. Then been advise on checking mixture screw adjustemnet. Most likely the primary throttle plates are too far open and are exposing the transfer slots. if one is blown it will allow excess fuel at idle and thus your idle mixture screws won't work but if you don't have the carb adjusted right along with enough timing and you have the primary's open too much then it also will render the idle mixture screws to not adjust and work and give the false reading of thinking of a bad power valve and it …. Some people think you're supposed to turn the idle mixture screws all the way in, and then back them out 2 1/2 turns. Idle Mixture Screws – Adjustments and How to Purchase. As long as when you screw them in farther, the engine stalls, you are ok. Set the Idle stop screw (speed screw see fig 1) by backing out the Idle speed . Holley 1850 idle screws turned in all the way, motor still idles. YESTUNE Motorcycle Idle Mixture Screw Carburetor with Accessories Replacement Carburetor. You will regain mixture control once again. Fights using the idle mixture screws too. Fits 2300, 4150, 4500 & 4160 Series Holley Carburetors. That 4779 is a great carb and easy to get right. it too far down it might have bent the tang on the float. Both the Holley AA-1 and the Stromberg EE-1 have removable idle jets, so if a leaner idle mixture was desirable, leaner idle jets would have been used. I removed the screw and shot carb cleaner until it came out the idle bleed and it helped the overall carb running but still no affect on that one mixture screw. Turn the mixture screws, alternating. 70 Part# 26-110-10 Add To Cart Overview 2 per pack; includes cork gasket Features: Accessible Large Head Style About Holley Holley Performance Products has been the undisputed leader in fuel systems for over 100 years. 040" SIFRs were contributing too much fuel at idle, with the primary idle mixture screws only at about 1/4 turn out. Answer: Original Question: “How do you adjust the idle mixture screws on a Holley carburetor?” NOTE: THERE ARE NO “SENSiTIVE IMAGES” (NONE, ZERO, ZILCH) IN THIS ANSWER. The car will actually barely idle with the primary idle screw (the one This is because the idle speed adjustment screw is in too far and . Strangely, it has intermittent idling issues, as the throttle speed varies when the throttle is released after high speed. Click to expand So if 3 1/2 turns. The throttle blades of the primary bores should be almost closed. It is a 327 SBC from 67' that has a 350 crank in it. To set idle speed without resorting to the stonehenge method of drilling holes in the primary plates - Holley has this little screw that. Rule of thumb with idle mixture screws is, bottom out and back out 1 1/4 turns and go from there. Continue adjusting secondary opening and idle mixture. I would check for vacuum leaks around the base of the carb. Then fine tune the idle with the primary. - screw in all mixture screw until it lock. - screw out all mixture by 1 turn and half. Holley mixture screws open too far. (2) Estimated to ship direct from manufacturer on 09/29/22,. being set too far open inhibits the idle mixture screws from managing the idle . I have a 355, extremely mild with a Quick Fuel BD 1957. That cam will want a LOT of initial timing. Holley Idle speed issues (4150. Using a vacuum meter Hook the vacuum meter to one of the vacuum ports on the intake, or the carburetor. To have the correct mixture when the blade is near the bottom of the slot, the large amount of slot acting as bleed requires that the upper (screw in) bleed be relatively small. By opening or drilling it will allow the primary throttle plate to close so not to be in the "Transfer" slot. We will approach this story using a typical Holley four-barrel 750 cfm vacuum secondary carburetor with two idle mixture screws. Learn More Lowest Price Guarantee Add To Cart Holley 26-101. a fair bet that the butterflies are too far into the transition slot. You may need to reset the idle mixture screws and repeat the process. Warm up the engine until the thermostat opens, and ensure the throttle shaft is on the hot-idle setting (that's the adjustment on the left side (driver side) and off of the choke's fast idle setting. A normal setting for idle screw set up is 1-1/2 turns out from close. Also as soon as you open the throttle the idle circuit. First, if you're running a dual plane, I suspect a vacuume leak on one side which makes the idle circuit ineffective. First make sure that both mixture screws are adjusted to the same setting. Install a vacuum gauge to a full manifold vacuum port. The primarys were opened too far and the machine was definatly off of the idle circuirt. As far as I can tell nothing has been altered in the carb. A typical starting location for these idle mixture screws is between 1 and 1 ½ turns out from fully seated. 080" and i noticed that the timed. Once the screw is fully closed, turn the same screw counter-clockwise one and a half turns. If your idle is too high, back your new secondary screw out a bit, if it's too low, screw it in a bit. I checked the idle mixture screws, and found they were about 2 1/4 turns from bottomed out. This happens when an aftermarket cam is used and the idle screw needs to be. For the most part, you will be working away from the fan. TURN IN IDLE MIXTURE SCREWS UNTIL LIGHTLY SEATED. smokes at idle, smell fuel, black smoke). If the engine speeds up, the mixture is lean, if it stumbles, the mixture is rich. What the idle mixture screw does NOT do. If the idle speed gets too high with the best adjustment, lower the idle speed with the screw on the side linkage. Holley Mixture Screws unresposnsive. I just rebuilt it with a "Holley" kit and put the standard (4. 040" You can check with feeler gage or drill bits. Holley 1850 idle screws turned in all the way, motor still. 66gt500 363 Aug 28, 2011 #2 Personally, I have never worried too much about how far out the screws are as long as they are about even and not out too far, like 4 or 5 turns. Adjust the fast idol screw so that the slit is just peeking or that you can just barely see. You will need to adjust the mixture screws as you simultaneously adjust the idle speed with the idle stop screw. Are you aware that the 4779 has 4 corner idle ? You have 4 idle screws to adjust. The typical idle circuit on many modern downdraft carburetors will consist of: (A) an idle jet, (B) the idle bypass, (C) the idle restrictor, (D) the idle air-bleed, (E) the idle passage/port, and (F). This being the case, you can't purchase "official" idle mixture screws now. If the throttle plates are into the slot your screws won't function. Take out the secondary idle screw and turn it over,then went you want to adj open up the secondaries and turn the screw sdluck, Aug 16, 2011. If I adjust screws in to get into high 12s to mid 13s idle becomes rough, low 14 screws 1/4 turn out and idles real bad. The problem is the idle mixture screws do not have any response, turn all 4 in to seat but engine will keep running. (2) Estimated to ship direct from manufacturer on 09/29/22, pending manufacturer availability. I have no history on this carb ,came with car The idle air screw adjustments have no Be careful not to get things too far backed off, . 5) There may be a slight vacuum leak at the carb base. Is there a problem with the metering block. When the throttle blades are opened far enough at idle to uncover the transfer slots, this adds idle fuel that is not controlled by the idle mixture screws. You have something going on with your carb. Next, back them out 1 full turn and restart the engine making sure the choke is completely off. Unresponsive Holley idle mixture screws. You may be able to add a little timing as well. Turn them out to add more fuel/air mix and turn them in to reduce the amount of air fuel mix. Turn the screw counterclockwise and clockwise 1/2 a turn from the middle position and listen. Most of my 4 corner idle Holleys have 1/2 to 3/4 turn out. Other issues may be your ignition timing, mmore specifically the amount of advance. Been asked this question alot: "What happens when I screw in/out the metering block mixture screws; When I turn them in, is it leaning the . 5 turns out and using a vacuum gage, but that just had me backing the screws out further and the truck ran worse.