How To Lean Out A Holley Carb

Doing this with a stock carb can be dangerous as the power valve circuit flows a significant amount of fuel and losing all of that fuel when the valve closes will create a lean condition. Holley mechanical and electric fuel pumps are designed to deliver the pressure and volume needed for performance use. RE: Holley Idle Circuit Mods - Mustangmike - 11-04-2015 Hey Mike, I needed to cross reference the part number on the carb to get the model # on Holley's site. Everything is brand new and has 400 miles on it. Holley carbs come with a standard shooter size which differs by carb list#. Check the body for cracks around inlets. Extreme part throttle lean out, Holley HP Greetings. After talking to Holley tech, I replaced the factory regulator and problem solved. In producing these parts, Holley prides itself in utilizing the latest technology in a lean environment to provide the highest quality parts at the best value to the customer. I adjusted the electric choke dial towards lean, thinking it's too rich on startup but that doesn't seem to make a difference. Align the gaskets, cover with a light coating of grease to prevent sticking, and torque to spec. most carbs, the adjusting screws are turned clockwise to lean the mixture and counter-clockwise to richen it. i don't know if you have solved your carb prob yet or not, but if not, we have a great sponsor-Bigs Performance Carbs, from altoona, wisconsin, we used a 4412 that they sponsored to us last year on our street stock, and never had one prob with it at all. I usually go by the spark plug deposit to inspect the fuel mixture. Whether you have a CCS Performance or a stock HOLLEY® carburetor (or a flow-modified CCS model), jetting should be fairly close if the carburetor is used in the intended application. The only way I know to lean out the carb is to read your plugs and jet down or up to get it right. First, turn in the mixture screw until the engine dies or runs worse, then back out the screw (recommend turning ¼ to ½ turn at a time). If it does you know that in the rpm range your having the issue with you need to richen up your mixture. Setting up and adjusting SU/Hitachi carbs on the Datsun Roadster by Keith Williams First things first. Hesitation when I would get on it (seemed like a lean condition)everytime and very week topend. It also gives gas while the carb switches from the idle circuit to the main circuit. How To Tune Holley Carburetors. Model T Carburetor - Page 1 of 18 Sort: [Please Select A Sort Order] Item Popularity Newest Items First Item Number (0-9 A-Z) Item Number Descending (Z-A 9-0) Lowest Price First Highest Price First Description (0-9 A-Z) Description Descending (Z-A 9-0) - Per Page: 10 Items 20 Items 30 Items 40 Items 50 Items 100 Items. This is how I baseline a Holley 4150 Double Pumper carburetor. If air is forced past the carburetor it can siphon fuel, causing the engine to run lean. I think mine is a 4160 Holley, but its been 7-8 years since I added and tuned it to the engine. After talking to Holley tech, I replaced the factory regulator and problem solved. It was used on both Federal and CA engines. At high rpm fuel flows from every orifice in the carburetor whether it is supposed to or not. If I lean it out too much there are a couple cylinders that are fuel starved (too lean) and start to misfire. Jets are broached. Leaning out a carburetor will increase the fuel economy and possibly increase the power to a certain point. Note: This is only a rough estimator of carb sizing. It runs well with full choke. Holley carb part throttle stumble. Carb manufacturers already know how much fuel a carb flows, and the factory setup is fine for 99 percent of motors out there. Carbs with removable high-speed air bleeds invite calibration problems initiated by the unwit­ting tuner. I ended up with a 50cc pump and. A carb running rich, as well as a carb running lean, can cause an off-idle stumble or hesitation upon acceleration. Popping out the exhaust could be most anything, but if you're way too rich that can happen as well. The other two carburetor types were manufactured by Chandler Groves (later Holley Carburetor Company) and Chandler Evans Control. Only the odd ball Holleys made for fuel economy work by turning in to richen. When a hood scoop or external air intake is used, it is highly suggested that the carburetor be sealed to it. 6280: 2 BBL Holley: 2346: CALL : 1985: ALL: 8: 318" - 5. The Holley Truck Avenger is one of the worst carbs to try to run with economy in mind. my truck stalls when i punch it and occasional backfires, and has alot of black smoke when i gun it. The secondary side of this carb does not use a power valve to balance the fuel flow between the primary and secondary, so it uses 6-step larger 73 jets. and sometimes when i turn the truck off it still stalls and backfires. In order to truly tune my carb, I want a better understanding of the symptoms of lean vs the symptoms of rich. The main system is designed to operate and flow enough fuel either way as a 2 or 3 circuit. The M4M is the emissions Q-Jet introduced in 1975, which has had certain adjustability added in while some of the off-idle power transition is taken out. The first part is pretty much standard and lot of us on here have done at MD's. Almost everybody has a Holley carb but not everyone know how to tune them we show you how and help you learn the science and basics of carburetors. If you have a carburetor with a power valve, you can change to a power valve that opens at 4. Holley carb part throttle stumble. 5 lbs vacuum use a 6. The secondary side of this carb does not use a power valve to balance the fuel flow between the primary and secondary, so it uses 6-step larger 73 jets. type carbs employ a “reverse idle” system in which adjusting screws have to be turned counter-clockwise to lean the mixture. most 4 barrel carbs have 2 idle air scews the holley im working with has 4 i have used a vacumn gauge but have not been very sucessful this is on a 1969 chevelle ss 396 slightly mod. Be sure all. Attach the throttle plate to the shaft with the screws so that the numbers on the throttle plate face the idle mixture screw and the dimples face in. Could someone tell me how to lean it out. If you come across this problem, replace the hose with a new one. Starting at: $325. Air screw adjustment should be made at >2000 rpm. A leaking, burned, cracked, or stuck valve could be the cause. Holley carbs come with a standard shooter size which differs by carb list#. I finally got around to remove my holley 750 and putting on my speed demon 750 dp. 5 out of 5 stars 181 product ratings 181 product ratings - Holley Performance 0-80457SA Classic Street Carburetor. Too much fuel pressure tends to make the carb run rich at low speeds, while too little fuel pressure might cause the carb to run lean during high engine speeds and loads. Take tank and top center air box off. My holley carb wont stop cutting out? how do i adjust my air mixture screws. Whether your a professional mechanic or a novice this video will show you all you need to know to properly set the idle mixture. There is more to your bog than just leaning out the Carb. Then turn the adjustment about 3/4 turns counter-clockwise and start there. After you get the primary side dialed in, bring the secondary back into play. I have a 600cfm Edelbrock 1406 carb on my 350. But don't lean it out to the point where the engine begins to stumble. What I don't know is if Holley still makes them. 4- Adjust air screws (one carb at a time) for highest idle RPM with a warm engine. How much does the cold weather lean out carb engine. WOT - Anything over about half throttle reduces manifold vacuum to a point where the power valve should open. A rich pilot setting will result in hard starting, plug fouling at low RPM’s, sputtering as the throttle is cracked opened. Ford Small-Block Engine Interchange: Induction System All 221, 260, 289, 302, 351W, and 351C 2-barrel engines were originally fitted with dual-plane iron intake manifolds and the venerable Autolite 2100-series 2-barrel carburetor from the factory. Racing Air Filters are often the reason for too lean carb settings. The popularity of the carburetor has waned in recent years. Holley carbs come with a standard shooter size which differs by carb list#. A simple jet carburetor cannot maintain the needed air/fuel ratio under varying suction levels and becomes too rich at high suction levels. The M4M is the emissions Q-Jet introduced in 1975, which has had certain adjustability added in while some of the off-idle power transition is taken out. make your float adjustment first with the engine running so that fuel just tries to barely creep out the hole you don't want it to be pouring out. think there was an article in one of the wheeler mags with an article on how to mod them for off road use. When the vehicle is cruising down the highway the mixture needs to lean out considerably if good mileage is to be achieved. Now watch out for a loose needle adjustment. This is very important, since if you allow the engine to overrichen on the line and the temp of the combustion chamber drops , you can cheat yourself out of an easy 25 to 100 HP depending on the size of the engine. need some advice on tuning a weiand tunnel ram with 2 new out of the box holley 600 vac. I actually use a small, broken drill bit that's just the right size. Re: leaning out a Holley HP at idle. Page 1 of 2 1 2 Next > If I lean them out more, the low. The main system is designed to operate and flow enough fuel either way as a 2 or 3 circuit. turn it back out till it runs smooth and keep turning out till it again runs poorly. Follow the Edel. C&S recommends: Belt Driven Fuel Pump 4000 series, -10 line kit P8020, Fuel Filter 2150, Fuel Log 4604, Carburetor to log fitting P8010 and Return line kit P8025. New 3-14-01 This tech paper will discuss basic set-up and tuning of Holley vacuum secondary carbs for optimum street performance and drivability. Make these adjustments ¼ turn at a time. Space between the shaft and worn bushings can allow air to get in and lean out the fuel-air mixture too much. The car will idle in the garage for an hour and barely make it to 180 degrees, but at the track within 5 laps the temp is 230. The problem with Holley carbs is that they are gas pigs. Increasing the size of the intermediate bleed will lean out that circuit. Its a Holley dual feed not sure on the cfm probably a 750. I believe the Holley HP 750 to have an inherent problem of leaning out severely at part throttle tip in as the vacuum decreases, but not before PVcomes in. The nomenclature only indicates the choke configuration. but the old setting was pretty close to my new one. I have a 79 TA that in the early 80's my ex put NOS on it and it stuck on and damaged my quadrajet carb-it would idle high. If the carburetor is adjusted to make it work well at high speeds, it will be too lean at low speeds. I'm probably going to ditch the 18r distributor and put all of the ignition back to the stock 20r stuff that worked with the old motor, just to rule that stuff out. A 200CFM 6224 Holley Bug Spray would be sized almost perfectly for these and would run well right out of the box. 383 cid chevy. I'll second that! When I got my 55, it's mild 350 had a 1407 carb on it. If you have a bit of a stumble in very light, low speed operation, sometimes it helps to richen it up by another 1/4 turn. Not on a stock CV carb. When a hood scoop or external air intake is used, it is highly suggested that the carburetor be sealed to it. This is how I baseline a Holley 4150 Double Pumper carburetor. SU carb leaning out and the starving - posted in Engine: I have a 179 with a 3. • BSA & Triumph used Concentric carbs with removable pilots jets (124/026) in 1968 only. Carbs then get stripped and redyed back to the original color. Google: "holley idle fuel channel restrictor" for the how-to on inserting wire (from. 038-inch PVCR. White or light grey spark plugs. Which way do I turn the mixture screw to lean out the carb. holley carburetor backfire problem!!! Post by woomahodal » Tue Nov 28, 2006 7:02 am i got a brand new holley 390, put it on, tried adjusting the float level and fuel mixture as best i could, but it backfires through the carb at any rpm higher than about 1500. An eccentric bolted to the front of the camshaft actuates a mechanical fuel pump, which is mounted to the driver side of the timing cover, and this supplies fuel to the carb. I have the holley 4150 hp 830 cfm annular booster carb on my 408 sbc. Re: Power valves for Holley carbs I am jetting a carb that was built by Nickerson Performance. I have had a look around other forums and seen a bewildering array of stuff that has confused me. Re: Need Carb Tuning Advice Again 8896 Holley 1050 TravisRice on September 27th 2010, 5:12 pm My 1250 Pro-Systems carb ended up being in the. There are subtle differences in the kits, so be sure to use the carburetor number and match to the list contained in each carburetor kit. 0 intake with adapter on the 2. Run the boat at high speed and repeat the procedure if necessary until the carburetor is adjusted for high speeds. make your float adjustment first with the engine running so that fuel just tries to barely creep out the hole you don't want it to be pouring out. Another good thing about the Q jet is that they are common as hell. Before the purchase, I made a couple of calls to satisfy my curiosity about this carb which, as many have pointed out, looks strangely like a Holley 4010. Upgraded it a few years ago from the stock exhaust and intake to a much higher performance setup. The secondary side of this carb does not use a power valve to balance the fuel flow between the primary and secondary, so it uses 6-step larger 73 jets. Overdrive Transmission Compatibility When using a Holley vacuum-secondary carb on a vehicle with a non-electronic overdrive automatic transmission, such as the 200-4R or 700R-4, a throttle kick-down bracket must be used. Though it started and ran good, it was dumping fuel and would not lean out to AFR set points. I need some help. I adjusted the electric choke dial towards lean, thinking it's too rich on startup but that doesn't seem to make a difference. The big four suppliers of 4 barrel carburetors today are Edelbrock, Holley, Quick Fuel and Barry Grant, each of these carburetor designs have strong and weak spots. The problem with Holley carbs is that they are gas pigs. On a 350 motor I would at least jet and use the metering rods on the primary circuit of the front carb based on the 500 cfm specs as a base starting point. The car will idle in the garage for an hour and barely make it to 180 degrees, but at the track within 5 laps the temp is 230. Then turn the adjustment about 3/4 turns counter-clockwise and start there. Carbs wear out just like any other component. The carburetor that we would recommend is based on how the customer will drive their car and the engine package that is in the car. :shrug: car is running rich how do you. Anything less than a 59 jet causes a lean flat spot. Turning the screw out makes the idle mix-ture more rich. How to Install a Holley Carburetor in a Chevy 350 By Bruno Silva on Dec 04, 2009 with Comments 0 Holley carburetors are considered as the most widely used as well as recognizable high-performance carburetors available in the market. I'm sure it's leaning out. Lots of folks lately with Holley issues. I have the holley 4150 hp 830 cfm annular booster carb on my 408 sbc. Also, what carb do you have? If it's a Holley, the number is stamped on the air horn by primary inlet. 5 out of 5 stars 181 product ratings 181 product ratings - Holley Performance 0-80457SA Classic Street Carburetor. I am gitting ready to put a motorcrfat 2150 carb on but i need to passs emisions now wiht the carter carb on. A carburetor might require rebuilding or replacement if a sticky needle valve is starving the carburetor for fuel or there are air leaks within the car part itself. 5 AFR and I have my power back. • Two stroke concentric's spray tube is cut on a slant. Played with it some and decided that 500 CFM was just way to big. TUNING CHALLENGE 2. It will require that idle screw is turned to increase RPM for the cylinder to be adjusted. i don't know if you have solved your carb prob yet or not, but if not, we have a great sponsor-Bigs Performance Carbs, from altoona, wisconsin, we used a 4412 that they sponsored to us last year on our street stock, and never had one prob with it at all. If that doesn't work then consider going to a richer main jet. All of Holley's models are rated in cubic feet per minute (cfm) with the smallest four-barrel rated at 390 cfm and ending with the Dominator line of racing carbs that now extends to 1,475 cfm. I am gitting ready to put a motorcrfat 2150 carb on but i need to passs emisions now wiht the carter carb on. The 500 & 600-cfm carbs can be modified to avoid an off-idle lean condition, so they can work well on a low boost pressure single or dual carburetor set-up, but we avoid the 750 and 800 cfm AFB�s on street driven blown engines because of a lean at part throttle problem that is inherent with this type of carburetor. First of all the carb is the original one but it is not new. The car will idle in the garage for an hour and barely make it to 180 degrees, but at the track within 5 laps the temp is 230. turn it back out till it runs smooth and keep turning out till it again runs poorly. I think mine is a 4160 Holley, but its been 7-8 years since I added and tuned it to the engine. You may can contact Holley any way, and get the information with out knowing the numbers. its a 670 cfm double pumper? how can i get it to stop cutting out oh and its not to much gas cause i got 13 to 1 compression. Screw the idle control screws in or out will allow more or less (emulsified) fuel to exit the carb. Your carburetor is a crucial part of your engine, and without a working carburetor, you won't be driving anywhere. in a lean condition until I get up to the desired speed and ease out of the throttle a tad to hold it. Could someone tell me how to lean it out. Take the plugs out and if they look clean you're good to go. The optimal carburetor setting is found when the engine performs well in cold state, when the choke is applied and revs up evenly in warm state. s for that carb. If you come across this problem, replace the hose with a new one. Thankfully, adjusting the mixture on a Holley carburetor is quite simple, as the mixture screws are located on the outside of the carburetor and can be quickly adjusted with a screwdriver. Check the body for cracks around inlets. I air fuel mixture is wrong and i need to adjust it but worried about messing it up more. The carb adjustment helps lean or enrich the fuel air mixture. 1) Turn both carbs' adj. The carb has main and secondary replaceable jets with its sizing numbers on its face. its a 670 cfm double pumper? how can i get it to stop cutting out oh and its not to much gas cause i got 13 to 1 compression. For example R-4776, or R-4776-1. Troubleshooting Your Holley Carb August 2, 2017 Wayne Scraba Fuel Delivery , How-To and Tech Tips , News 1 Holley carburetors find their way onto countless vehicles, from race cars to hot rods to delivery trucks, and for good reason: They're the standard of performance, and without question some of the most popular and easily tunable. I ended up with a 50cc pump and. 5 turns out and see if it gets better. I'm probably going to ditch the 18r distributor and put all of the ignition back to the stock 20r stuff that worked with the old motor, just to rule that stuff out. I've heard ghost stories of how hard is to adjust the float on these Holley Carbs and i've recently build a big block 350 to the best of its ability and heard that Holley's we're the best to get for maximum performance. How to tell what size carb you need: You take the engine cubic inch and multiply by the maximum RPM and divide by 3456. Think siezed pistons and chewed out bearings Running too rich will usually smoke and lack power, it will foul up spark plugs and smoke you out, but it shouldn't kill the saw. 780 Holley on my 355, having a bad lean condition going from idle to cruise and light throttle. where to buy holley carbs in UK. here's the engine layout. " 3 "People think carb gurus can get more power out of a motor because they make the carb flow more air, but that's not true. ? should lean it out. how to install a low cost holley 2 barrel carburetor The Holley 500 cfm $300 2 barrel seems to be it if a way can be found to lean it. It's acting up. If one is wound out and the other in, the car will stay running, but one side of the engine will run rich and the other side lean. Let us know how that goes, and we'll continue the virtual tune up then. Explanation: A lean code is enabled when the computer has detected enrichment adjustments have maxed out, with no results, this inability triggers the lean code. I adjusted the electric choke dial towards lean, thinking it's too rich on startup but that doesn't seem to make a difference. If you have a carburetor with a power valve, you can change to a power valve that opens at 4. I am gitting ready to put a motorcrfat 2150 carb on but i need to passs emisions now wiht the carter carb on. Space between the shaft and worn bushings can allow air to get in and lean out the fuel-air mixture too much. Install the throttle shaft seal with the sealing lip down in the carburetor body until the top of the seal is flush with the top of the carburetor. That would be great if it was that easy. Make these adjustments ¼ turn at a time. It will vibrate out of adjustment if your needle valve clamp nut is not tight enough. Then a huge rich dip in the midrange. In order to check for the proper jetting at the main jets, new spark. Once this has been done, we can move on to the carburetor. In some instances this can cause the machine to "bog" as if it were actually running out of gas. Possibly damaged by a backfire condition. NOTE: Holley carbs also have a secondary idle speed screw, and it should be adjusted in a similar fashion. Once the carburetor is installed and the engine is up to operating temperature (Holley carburetors float level adjusted first) choke fully opened the fuel mixture can be adjusted. 035 shooters cured that. The main system is designed to operate and flow enough fuel either way as a 2 or 3 circuit. Overdrive Transmission Compatibility When using a Holley vacuum-secondary carb on a vehicle with a non-electronic overdrive automatic transmission, such as the 200-4R or 700R-4, a throttle kick-down bracket must be used. Practically all stock 340-6 bbl. I am thinking it may be a power valve issue as i my laptop is in my truck at work and i can check vacuum but i am running the same power valve as before. On these carbs, the idle mixture screws not only impact the idle circuit but also the first 1/8 throttle. So this motor and carb ran good for 3K miles then started doing this? Important to know in order to figure whether it is a set-up problem or a failure problem. When I stop the car the engine idles very fast so then I have to push the choke in again until I start out again and have to pull it out so it doesnt backfire. If air is forced past the carburetor it can siphon fuel, causing the engine to run lean. out and installed just a regular electric pump straight to the filter to the Carb. Most carb builders compensate for this by closing the power valve to lean out the mixture as the vacuum increases at higher rpm. I have tried balancing the carb out beforeI still cant get the rich issue to go away. You may need to turn them out a little, try 1. So if i just wanted to lean it out a little which way do i need to turn the mixture screw. Needle Clip: This is the small circular clip that is used to adjust the needle position. It ran fine at this setting previously but has now started acting up. In warm air conditions, you have to jet down the carburetor to lean out the air/fuel ratio. Holley List Numbers - Holley Carburetor Identification. WOT – Anything over about half throttle reduces manifold vacuum to a point where the power valve should open. The Ford book reccomends 2 1/2 turns rich then lean it out. Carb Class: 5 Basic Carb Tuning Tips By: Quick Fuel 12/22/2015 < Back to Blog Home Quick Fuel Technology® (QFT™) ships carburetors only after they have been thoroughly run-tested and adjusted on a typical engine. here's the engine layout. i don't know if you have solved your carb prob yet or not, but if not, we have a great sponsor-Bigs Performance Carbs, from altoona, wisconsin, we used a 4412 that they sponsored to us last year on our street stock, and never had one prob with it at all. you want it to be set so that. The engine should pick up speed and begin to smooth out. 0 intake with adapter on the 2. I have a 90 jeep wrangler 4. A Holley carburetor can be leaned either through the idle circuit or the main jets. The motor is fairly warmed over with heavily ported aluminum AFR heads, roller cam, headers and Edelbrock intake w/. I currently have a edelbrock carb on my 454 chevy motor. Most carb builders compensate for this by closing the power valve to lean out the mixture as the vacuum increases at higher rpm. This is very important, since if you allow the engine to overrichen on the line and the temp of the combustion chamber drops , you can cheat yourself out of an easy 25 to 100 HP depending on the size of the engine. 5 AFR and I have my power back. This means checking all the hoses going to the carb and intake manifold for any cracks or loose fits. 3 crank, it has a eaton m90 blower running at 7psi, it has one 2" HS8 SU with the highest flowing grose jet needle & seat valve, it has a KX needle wich is about as rich as i can get, very thin and fragile, i have just fitted a brand new needle and main jet becuase the last one was slightly bent. We tend to stay around the 71 to 75 jet range. The bog or hesitation may be caused by a momentary lean condition when the carb goes from the idle throttle position to the main metering system. 2L Service Carburetor Manual cause an holley 2280 carburetor to flood to more lean; how to adjust carburetor on 82. I actually use a small, broken drill bit that's just the right size. The carb has main and secondary replaceable jets with its sizing numbers on its face. A typical Holley carburetor has two screw-in jets that meter the amount of fuel that flows to each primary venturi. Dropping the jetting it made a tiny bit more power, but it starts to get a little lean on the top end without fully get rid of the dip in the middle. 050 squirter and brown cam(the biggest you can run on a 4150) and it still had a hiccup. Just remove the top screw and turn the nut out and it will withdraw the needle and seat. 035 shooters cured that. Is mixture screw turned in or out to lean carburetor? How do you lean idle circuit on a 650 holley? Turn the idle mixture screw in to lean the mixture, out to richen the mixture. The only thing I have touched is the idle adjustment. Power valve blown out by spitback up through carb. Backfiring through the carb can be an indication of being too lean - this is not a good thing for your blower build. The bog or hesitation may be caused by a momentary lean condition when the carb goes from the idle throttle postion to the main metering system. The level of fuel in the carburetor bowl is critical: too low and the carb will run lean, too high and it will run rich. WOT - Anything over about half throttle reduces manifold vacuum to a point where the power valve should open. A typical Holley carburetor has two screw-in jets that meter the amount of fuel that flows to each primary venturi. the plugs are white and have even burnt the tip off a few times. How to adjust my holley carburetor on my ford? I have a 4 barrel Holley Carb model number 2885 I think, on my 1968 f250. If used, these early BSA & Triumph carbs should also have 622/235 update kit installed. Holley points out there is a chamfer around that hole that has a strong effect on what that jet flows. Short answer - a carb can't give you a horsepower increase. Reconnect the throttle and transmission kickdown linkage and throttle return spring (Holley P/N 20-89). on most carbs like holley full manifold vacuum will usually be on the base plate. I'm with mountian motor of the Demon carbs. It was used on both Federal and CA engines. How to adjust my holley carburetor on my ford? I have a 4 barrel Holley Carb model number 2885 I think, on my 1968 f250. The carb has main and secondary replaceable jets with its sizing numbers on its face. Is the 600 CFM Holley going to work on a stock 454 motor, at least till I can get a 750?. Holley 635cfm vac with Wilson 1” four hole spacer. The main system is designed to operate and flow enough fuel either way as a 2 or 3 circuit. The M4M is the emissions Q-Jet introduced in 1975, which has had certain adjustability added in while some of the off-idle power transition is taken out. If it is at idle adjust the ilde mixture screws and go from there. I need help on how to lean my Holley 600 out. For starters: It's a Ford Bronco with a 300 I6. Requires excessive amounts of choke to run/start. Re: Need Carb Tuning Advice Again 8896 Holley 1050 TravisRice on September 27th 2010, 5:12 pm My 1250 Pro-Systems carb ended up being in the. My replacement carb ran great, so they're good in that aspect, and I image if you're a bolt on and go kind of guy, you'll never run into this issue. I cleaned out all the passages including the idle bleeds and passages and they are all clear. Too much fuel pressure tends to make the carb run rich at low speeds, while too little fuel pressure might cause the carb to run lean during high engine speeds and loads. Just had to add some fuel with the accelerator pump squirter and cam. Turn the shaft until the flat side is facing out. Turn in screw gently until it stops, do not use excessive force or carb body will be damaged. Crank engine (ignition "off") with air horn removed to fill float chamber. Leaning Holley carb midrange I have a great idle AFR and “good” high RPM AFR. Now watch out for a loose needle adjustment. im not a holley fan so i didnt keep track but help is out there good luck. Not only will you see an increase in performance, your engine will idle and run better than it does with that old worn out factory carburetor. I air fuel mixture is wrong and i need to adjust it but worried about messing it up more. 2) Lean Mixtures means the carburetor is delivering too much air. Next turn the idle mixture screw out until the rpm’s start to taper off. If that doesn't work then consider going to a richer main jet. 16-H-12 NOTE: Some models of the Holley 1920 carburetor may vary slightly in general design and appearance from others, but basic cleaning and adjustment procedure will remain the same. Doing this with a stock carb can be dangerous as the power valve circuit flows a significant amount of fuel and losing all of that fuel when the valve closes will create a lean condition. the new one is very slightly more in the lean direction, maybe 1/8 turn. 04) in all cases. Stock carb. If you notice these symptoms, tune your Demon carb in your garage for improved engine performance. And they run miserably when you try to lean them out. NOTE: Holley carbs also have a secondary idle speed screw, and it should be adjusted in a similar fashion. Just had to add some fuel with the accelerator pump squirter and cam. When you remove a power valve from the metering block, you will notice a pair of small restrictors in the area alongside the threaded portion of the power valve (see photo). How to adjust my holley carburetor on my ford? I have a 4 barrel Holley Carb model number 2885 I think, on my 1968 f250. A jet set up for sea level, will run to rich at 6000 feet elevation. But don't lean it out to the point where the engine begins to stumble. Holley type carb, and labels the passages. Turning them in will restrict the flow of fuel to the idle circuit and lean the mixture. The float bowl mounts on the front of the carburetor and can be metal, or glass. If you have a bit of a stumble in very light, low speed operation, sometimes it helps to richen it up by another 1/4 turn. I adjusted the electric choke dial towards lean, thinking it's too rich on startup but that doesn't seem to make a difference. What you are looking for is an increase or decrease in rpm. Typically a carb backfire means too lean a mixture, or timing is too advanced. Almost everybody has a Holley carb but not everyone know how to tune them we show you how and help you learn the science and basics of carburetors. So if i just wanted to lean it out a little which way do i need to turn the mixture screw.