So if I clicked on this post I would immediately reply "it depends on what you have, what you want to do, and how much you want to spend" and ***ume someone new to carbs that doesn't understand that's a loaded question would ask. But I'm asking the question and not new to carbs. So I'm going to set this question in one single parameter: What is the best Carburetor in terms of how well it stays within the range of the AFR you set it up for. Any kind of changes your engines makes that will constantly change the AFR: wide open throttle, Fast accelerations, fast shifts, outside temp changes, temp changes inside the engine bay, barometer changes, al***ude changes, and even different fuels (when sometimes you put no ethanol and other times you don't). This idea started when I dipped my toe in the aftermarket TBI injection (fitech). I'll spare the details but after much headache it made me really appreciate a carburetor. What it did allow me to do is keep an eye on the AFR reading of the Fitech and at the same time the AFR gauge on another car with the Edelbrock AVS2 carb. IF there was a difference in how quickly the AFR adapted to changes, I didn't notice it! Yes I know in theory a mechanical device is racing the speed of an electrical signal. But that electrical signal still has to get it's input from an O2 sensor from the exhaust. My own observation and experience with carbs. That AVS2 was great! It has annular boosters which helps give a more precise mixture. I also can't help but think metering rods with theoretically infinite adjustments of an edelbrock is going to be much more precise than a metering block in something like a holley. I also drove a suzuki samurai around for a while that had a Harley CV carb. I didn't have an AFR gauge on it but if I didn't tell you it wasn't EFI you wouldn't have known. It ran good at angles, elevation changes, bouncing around, or whatever else you threw at it. Yes that's kind of cheating because it's probably the one practical application for a CV carb on a car I'm aware of. Finally I have yet to try it but I will soon be bolting up a motorcraft 2150 on a 77 bronco. Early broncos never had this carb just the very close relative: autolite 2100. The difference is the motorcraft I have chosen has a factory al***ude compensation device on it. Basically just a barometer that opens a new air byp*** to add more air when the air is thinner to keep it from flooding. It's also equipped with annular boosters and some of the last models even had metering rods they used to lean out the mix at idle. This is why I chose this carb. I have no experience actually running it but I expect good things! So what am I missing? Anybody have any data on AFR of different carbs and EFI? Or knowledge of what carbs perform the best in terms of keeping the narrowest range of an AFR?
To me picking a carb depends first on if the particular carb is the right size for your engine. All of us old farts knew that guy in town that had a 750 Holley on his stock 283 or stock 289 with maybe a high rise but all too often and adapter who could never get it to run right and always got mad when you told him the carb was just too much for the engine. Beyond correct size a reasonably common carb that you can get kits for at the local parts house or order "the good kits" from one of the "the good kit" carb kit vendors. That is pretty well HAMB friendly carbs with quadra jets thrown in to the mix. Then you have to actually like that brand and style of carb. I ran Holleys for years end because for me they were easy to work on and I cold jet one to have it do exactly what I wanted it to do. My buddy used to give me ones he took off engines he got just because he didn't want to fool with them and a couple ended up in the bed of my truck and rode around for a couple of days before I found them. On the other hand I get away equally well with Edelbrock or AFB carbs or Quadrajets and most two barrels. What I don't suggest is goiong odd ball just for the sake of going odd ball. A guy I knew back years ago decided that he was going to make a manifold to bolt a set of 750 Honda carbs on a little 4 banger he had rather than buy and available intake and put the carb most guys wanting more power out of that engine ran. I moved before he got it going and never did hear if he got it going.
In this "What If" case of choosing the BEST, I would look at the people that have no rules, all the ability to test, tune and select (time + money) and have to run them for an extended time and varied conditions. Drag is run a couple minutes at idle and WOT on a flat. Back to the pits and readjust. NASCAR is varied speed and over time, but limited by rules (single 4). This is probably closer to real world USA rodders and cost. The top end Holley stuff is heavily researched and has a huge amount of adjustment and parts choices. The top cl***es for endurance road racing or rally racing is probably closer to wide range extended use, and they tended toward Individual Runner (IR) multi carb stuff before FI took over. This applies to fewer cylinders and smaller displacement all the way up to the big block GT40s. You gain from tuning the intake without worrying about balance, at the cost of complexity and possible problems with dirt leaning out one cylinder. On the street, where flexibility (not having to constantly fiddle and tune) and cost are larger concerns, the single carb is going to be the common choice. Choosing between the different types will mostly come down to experience and availability. That time + money thing means most people do not have the ability to try out a half dozen carbs, get proficient with each and be able to select without bias. That's why it's often suggested to ask someone who has that experience to help with the selection, just like picking a cam. Given that typically you go out, buy the carb and might even get the tuning kit too, bolt it on, hook things up, then do some adjusting, the main thing is easy servicing and holding that setup. A step above is wide band tuning. A step above that is dyno tuning. Given the wide range of engines, carbs, usage and effort, there is also a wide range of BEST.
I might not have emphasized this enough in my original post and I had a misleading ***le. But the ONLY part I'm interested in for the purpose of this post is which carb stays within the set AFR range better than any others in the widest variety of conditions.
having put an AFR meter (O2 sensor) on a few different carbureted cars, I'd have to say, hands down, the Quadrajet is the best carb for keeping the mixture where you want it to be. Of course I'm talking 4bbl carbs...which is all that matters, right?
Having rebuilt a huge number of carbs back in the old days, I can tell you there will be no "best" winner here. No one did AFR tuning until after EFI was in use for several years, was not even heard of before then. The AFR was referred to as a properly adjusted idle with a goal of being close to 14.1 (which was seldom measured until an emission test was required). Carbs were at best considered as a "best combined compromise" between nasty weather operation and nice weather operation, and max performance and best fuel economy. In states with real winters, and real summers, most carbs were adjusted each spring and each fall for best operations for the upcoming season. States with less extreme weather changes were often spared the seasonal carb adjustments. Due to the mostly non-monitored fuel quality, the quality of the fuel across the nation also varied a lot. Another huge issue was most vehicles saw very poor tune up schedules, so often the condition of the plugs and points were so bad, and the state of carb adjustments were so far off, even the best carbs were handicapped. Between the "junk" (water and dirt) in the fuel and the poor state of tune many motors received, the carbs were often required to be rebuilt every few years (is 2-3 years considered long term?). Since the emission era, that started in 1968, but really stepped up requirements in the early 70s, the auto companies started adding all sorts of electronic gizmos to the carbs to make them meet the increasing emission standards. Most of those electronic gizmos fail miserably, so the auto companies tried some other gizmos, many of which failed as well. By the mid 1980s, very few American built cars and trucks were still be produced with carburetors. By the end of the 1980s, all American auto companies gave up on carbs because they could not be modified to maintain proper function for the 100,000 mile requirement the Government required through emission testing. The long answer to your question is, no carburetors fit into your question for keeping AFR consistent for long term, at best it was a compromised goal. The short answer is that one of the last production 4 barrel carburetors to be put on American production vehicles was an electronically controlled Rochester Quadrajet, so I suppose that would be the one that comes closest to being an answer to your question. If it would still be available would be a different question, and if the "brain" and the sensors that controlled it, are still available would be another question.
Gene's post above is spot-on with one minor exception. Emissions came to California in 1966, and the rest of the nation in 1968. Some time in the mid-to-late 1960's, Ford Motor Company (probably others) had a rudimentary AFR tester. We got laughed at for buying one at the auction of a Lincoln / Mercury dealer that went belly up somewhere around 1975. I experimented with it several times, but found it to be of little use as I had sufficient experience with the aftermarket Carters to set them from experience. One other minor detail: those electronically controlled Q-Jets that Gene mentioned were the "best" from an AFR standpoint when new, but in this neck of the woods, horribly unreliable. They may have made 100,000 simulated miles in a test laboratory, but I would guess I could count the number that made even close to that here in central Missouri without issues on the thumbs of one foot ! The fuel injected engines were not any more reliable at that time. It was not a good time to be the service manager in a new car dealership ! Jon
I suggested a normal non-feedback Quadrajet as the best carb for controlling mixture...and yes, they need to be maintained, mostly to keep them from leaking internally, make sure the diaphragms are ok, body is not warped, float is not sunk, and most importantly, that some idiot hasn't messed them up by not knowing how they work or how to work on them. The computerized ones were a kluge...automotive controls have come a long ways in the past 40+ years.
Yeah, those feedback carbs were not a step up, they were an off-brand band-aid on a plugged up preset wound. The factory service manuals were no help back then, either. I've gone back and revisited them a few times, and the systems were not described well, the ranges undefined and the root causes never explained. I feel for the dealer techs of the day, but as an independent tech, we had those same vehicles after the warranty was over. Everything was worn and iffy. Plugs worn to 80-100 thou, the rest of the ignition tired, feedback carbs or injectors plugged, every vacuum line questionable at best. Pay was stagnant and the complexity was growing. Everything getting tighter to fit all the stuff in. It's still going that way, and the recent news is still spouting how there is a shortage of techs and great pay, both of which are flat out lies. https://fortune.com/2025/11/12/ford...ade-schools-we-are-in-trouble-in-our-country/ EVs are rolling out and need less maintenance, and the pay is still not even keeping up with inflation. 25-45 flat rate, (note, this is all, not dealer) https://www.salary.com/research/salary/hiring/flat-rate-mechanic-salary#:~:text=How much does a Flat Rate Mechanic make?,Here’s a look at the typical salary range: while shop charges average 142.82. https://myautogms.com/blog/auto-repair-labor-rates-by-state-2025-guide
@RodStRace Is Chino Valley in Ca? Here Shop is average $200 I feel for ones that have to go to a shop, I dread the day I have to , Most so call tech Do not think p*** scan tool , Vehicle under warranty they do not want to spend time on and then when the warranty runs out they want to pick apart . I feel the Q J was reliable until the plug in bowl would leak ( bowl if I remember correct ) I grew up most gm & Holleys worked on many different cabs , personal and family.., When I started turning wrenches in my 30's I was working on OBd2 Fleet close to 4k of same model of each brands of Gm & Ford
Chino Valley is just North of Prescott AZ. I didn't guess labor rates, did a search and posted the source.
I officially started pulling wrenches in 1972. Did carb rebuilds, tune ups, brakes and suspension. Did that at independent shops until the early 80s. Then I went into a factory job that turned into a maintenance department job that turned into heavy machine repair (repairing clutches, brakes, and crankshafts on 200 ton forge presses. Because of a dumb move, I returned to the automotive world in 87 & 88 as a Chrysler Dealer Tech (just a few years into the new Chrysler EFI era) at a small town dealership, 3 techs did everything. The return to pulling wrenches ****ed. My wife had the ability to find every fault a carb could possibly have, It was a constant effort to keep a smooth running carb motored car running at its peak performance for her to drive. Those electronically controlled carb motors was a royal pain to keep functioning correctly for her to drive. Our first EFI car was a used 1985 front wheel drive Mopar that she happily drove 150,000 miles herself, without issues. That car had over 200K miles on it when a crash took it out. She has been in EFI Mopars since. The old beater Dodge trucks I drove were still carb equipped, but it was getting harder to find good rebuild able carbs in our area. I went back into factory work because the Dealer Tech job didn't come close to the entry point starting pay for a grunt job at the factory. My previous heavy machine repair experience moved me into the maintenance department shortly after I had started working there, for a few more years, until a health issue changed everything. A couple years later, I opened my own jobber welding shop in 1994 (mostly dealing with automotive structural welding). Once I opened my welding shop, my automotive experiences shifted towards the structural end of the automotive world. By 2011, I no longer had anything driven on the roads with a carburetor on it, everything I owned (except the mower) was EFI.
yeah, but it's fun to get back into after years without. Same thing with distributors, eh? I now enjoy struggling with the points in a few of my cars, vs having to be working on them all day every day like when I ran my shop 35 years ago, and happily swapped everything to electronics first chance I got. Now that they don't get driven every day, it's not so hard to get motivated to keep it running.
There's a few unusual answers thrown in there. It's like I'm asking, "what is the fastest bicycle" and the answers come back with, "bicycles aren't very fast you should drive a motorcycle instead." But point taken most people like EFI better. I would on a daily driver but don't for a cl***ic car. But for those that weighed in, it seems Quadrajet has the most votes. For about 10 mins K and N made a unit called, "Carbureted fuel injection." It was basically a carb spacer with a fuel injector built in. The fuel injector (ran off low pressure fuel T with your carb fuel line) had a computer and 02 sensor. The car ran mostly on the carb but the fuel injector made up the difference. So you'd set your carb to run a little lean, the injector would make up the rest when it needed to. It also gave the car a redundant fuel system if either would fail it could run on just one of them. I had a car I sold with one on it and it made the car run perfect. It depends but most of the time I prefer something besides a 4 barrel. Most people are guilty of overcarbing and most things come at a sacrifice. I'm a cruiser not a racer. I don't think I've ever attemped to get to 60 MPH faster than 10 seconds in anything or shifted above 5000 RPMs......... Thanks for the input on your AFR experience with the quadrajet.
There was a 2bbl version of the Quadrajet, also...the Dualjet. Missing the huge secondaries, so it was pretty low CFM. Not many of them around any more, and they also were built with computer feedback mixture control in the 1980s. I expect you'd see pretty good mixture control from the non-feedback type, if you could get one and get it working properly.
As a MoPar guy, always had great luck with Carter carbs. I have a few on the shelf as good cores for future projects.
I used to be a smog tech, so I've seen a lot of cars and trucks at idle and at 2500 RPM, then later on the test dyno (NOT a full on power dyno) at those same speeds. Q-jets and AVS were pretty good, thermoquads too. The Edelbrocks were typically too rich out of the box, which made them okay (safe) for just tossing on, but poor MPG and tended to start hot poorly and fail smog. Holleys were all over, because most had been messed with. AFBs were hit and miss, probably for the same reason. The economaster 4 bbl holleys were often too lean and hard to get good, unless they were new or had just been gone through. I have a feeling they were more susceptible to dirt. The motorcraft 4 bbls weren't seen as much, couldn't handle the crud as well as the Q-jets. Most 2bbls could be dialed in okay. The duojets would loosen up at the midsection, it was common to unbolt and tighten the screws underneath. The Motorcraft 2 bbls were worse than the Carter 2bbls for needing servicing. A lot of the Carters were worn out at the throttle shafts, though. A couple of carbs deserve special mention. They weren't commonly messed with so this may be due to lack of experience on my part. The CVCC carbs when right and all vacuum good were fine. Rarely needed to be unplugged and adjusted. But if it needed rebuild, Oh My! Just fiddly little boogers. The Ford VV wasn't great when 'right' and was a mess when wrong. Holley sold a lot of replacements for those.
Jim - yes, with that ancient tester I mentioned, not with any modern equipment. AFR was better than the Autolites and Holleys I checked. I disposed of the tester before I got anything with a Q-Jet, so cannot compare. Jon
There have been lots of cars which came out with constant-depression carbs: SUs of all kinds, including those made under licence by Hitachi, and Stromberg CDs spring to mind. More recently there has been the practice of racks of motorbike CV carbs on car engines. The SU HS2 on my Morris Minor was a thing of simple, elegant beauty. I know what you mean by it behaving exactly like EFI, only via the simplest of p***ive pneumatic servomechanisms instead of a lot of encrypted choreography. It was easy to set up, and once set up it kept its tune. Not a practical answer, but SU did make the downdraught D4/D5 types in the '20s and '30s. I saw four of them on a Lagonda V12. I have speculated about emulating the effect using a combination of 3D-printed and HS8 parts. How hard did Ford have to try to make so simple a concept so complicated?! You'd swear they developed the VV specifically to discredit the constant-depression principle lest it turn out to be a serious threat to the EFI they were doubtless already invested in — the way it did on motorbikes for about 30 years.
Why is it so important to maintain a constant ratio of fuel to airflow if the density and temperature of that air is not also part of the equation?
I don't know if I'll bother doing it or not, it seems to run ok. It does burn some oil, a quart every few hundred miles. Will it make a 3000 mile trip? Who knows!
I think Not so much the carburetor, Its more about intake design Especially dual plane , When tunning you have to pick where engine is going to operate be used @ what Rpm . Tune for there. On dual plane with O2s or Egt's on each Cylinder the Afr are inconsistent from Idle to wot, I wonder if OEM experimented with Diffrent plug heat range's pure cylinder ? & then decided to go with a Certain heat range & Rpm of operation 2,500-3,500 Afr .Typical driver , Not performance models that where produced and sold That where 6,000 plus rpms , Race on Sunday sell on Monday , & this is why in Aftermarket & OEM performance division you seen more intake runners equal length in single carb & some clocked for straighter path a tighter balancing of Afr ,, I also know more then just runner's , the Firing order , head design ect. Wonder if Carbs where still in production OEM if there would be a different heat range spark plugs per cylinders ,Split type intake have a door /****erfly In intake to switch from low end torque To mid upper range , I know a BMW & one of gm 4.3 v6 I believe used , those where Efi thoe . This where EFI individual injectors supersede when you have control over each cylinder, Like F1 & other forms of Racing & development which trickles down to Oem in engine operation not heated seats & back up cameras.
The Jalopy Journal
