33 years running the Q jet. Fantastic carburetor

I learned the first thing to do with a quad was take out the stock filter, throw it as far as you could, and install a good large in-line fuel filter.

I worked for a Buick dealership in the late 70's, the QJ was still everywhere. Those that hate them dont understand them. Yeah, they are a little bit different, but once you figure the design out, you realize the Rochester gang had more than a few Geniuses. On a GM 350 or 400 they just worked.

When you get the air door on a quadrajet set correctly the can be incredibly responsive. But most noobs end up with it setup to soft and have a huge bog when the air door tips in

QJet : the reason for the upside down lid

Here in Australia we have a fellow called Larry Perkins, legendary race car engineer and driver. With the early 308 Holden racing engines they used Holley carbs, then they progressed to twin 50 mm down draft Webber's to improve performance. But in the end they used the quadrajet and that carby produced the most power of any308 ever raced at Bathurst.

I went to college to be an industrial arts (shop) teacher and was able to take classes at the GM training center for credits. I took a week long class on Quadrajet carburetors. The first two days were carburetor theory. Wednesday morning was about how to tune and adjust the quadrajet, and after lunch we were each given a carb with purposely screwed up adjustments. We were to adjust them correctly and bring them to the instructor to be checked. My first carb was accepted as correct Thursday after lunch, the second was passed Thursday at the end of the day, and my third was passed mid-morning Friday. Once I knew what the instructor expected, it was easy. Later, I ran a speed shop and helped campaign a super stock K automatic 1969 Camaro with a 255 horse 350 with a quadrajet. That 3696 pound car set national records every year from 1976 to 1980 The last NHRA record it set was 10.91 at 120.80 miles per hour in 1980. Flat top pistons, small valve, large chamber441 casting heads, a powerglide, and 5.86 gear, turning 8 grand.

One of the biggest desighn flaws of the Quadrajet was tthe two front bolts going right through the carb. Every body tightens them down as if they hold the engine in the car. This overtightening then warps the top housing and the body quite severly resulting in both fuel siphoning into the primary bores as well as vacuum leaks. And no you can't file it flat or mill it right again. Once this happens the carb is junk. The gasket won't seal the accelerator pump dribbles, the emulsion tubes no longer do their job. Iv'e seen as much as 1/4" of warpage in these carbs. Step one when overhauling is to put a staight edge across the body and cover to make sure it is good to go.

Something that seems to always get overlooked with the Q-Jet is how good it is off-road. As someone who's driven across the Rubicon over 10x in different carbureted vehicles that Q-Jet did awesome. They had it all it one package when dialed in. Run great at steep angles, small primaries for decent fuel mileage at cruise, and huge secondaries for when you mash the peddle.

The unique sound of the "Quadrajet moan" is AWESOME! ❤

When I was younger it was common to hear guys call them "quadrajunk" But there were older guys who really knew how to make these carbs work very well and over time I started seeing them of course on stock class drag cars and my attitude changed towards them.

When I learned to rebuild QJets in college I found out what a sophisticated and flexible design it really is

Look at Nick's Garage. A few videos ago, they were messing with a GM engine. At the end, they bolted on the original m Quadrajet and was almost on par with the biggest carb they tested with. Although, a dyno setup has a great fuel pump setup.

Quadrajets are hard to beat for street and street/strip cars. They’re easy to set up once you learn them and the primary booster design is far superior to any squarebore carb. The small bowl can be overcome by windowed seats, larger seat orifice, smaller float, and removing a cast in wall in the bowl, they’re almost impossible to beat, and are almost infinitely tunable. There are Quadrajets going deep in the 9s now, and run like fuel injection on the street when set up properly.

Q jet carbs are one of the best carbs ever designed. People don't understand how they work or how to service them. GM created so many high performance Q jet carbs there's one perfect for your engine. Pontiac used these in their GTO engines.

I daily a 1982 Olds 98 Coupe with a 307 topped with a Q-Jet. It has 285k and idles like a kitten and is happy around 75-80 mph. I take her on road trips all the time with no drama.

Hi Uncle Tony. In another life I had a Holden Monaro with a factory Chev V8 and the Quadrajet. Everyone's going, Dave throw that away and get a Holly 650. Which I did ... and sold the Qjet for $100.00. But the car became very thirsty for everyday use and low down performance was unimpressive. So after awhile and some research I decide to return to the Qjet - I found a very reputable shop who provided a no smog Qjet and dyno turned the car. Suddenly the car had a amazingly responsive throttle and when those dinner plate secondaries opened up the car would push you back in the seat like never before. So it stayed with the Qjet while I had the car.

Between the primaries and secondaries there are a couple of void spaces. Make a small hole at the top and bottom of these into the float chamber. This increases the effective float bowl capacity somewhat. With a good pump there is no more starvation issue. Drill the accelerator pump orifices out slightly to eliminate bog. Qjets are very tuneable once you find out the tricks. I used to have a good book on the subject, but I think I gave it away years ago.

Model 2300 Holley 2 barrel is a rock solid carburetor for your daily driver. Super easy to tune also and they come in two sizes. That said, I'm putting a Q-Jet on my 318 when I'm finished with it.

Air passing through the primaries of a quadrajet has a chilling effect due to increased velocity through the Ventura, pulling some of the heat away from the fuel bowl.

Watching this video...I am remembering the smell of Berrymans Chem Tool 55 gallon drums in the 1980s.

I also always love the hard spot in the gas pedal with the Q-jet when you know the 4 barrel was going to open even on a little 305 in my old monte carlo .. it was just cool and then feeling the little kick of power

As far as street cars(every day driver) go, you cannot beat the reliability and ease of maintenance of the quadrajet.

quads have a warm memory for me. worked at a chev dealership in early 70's. we had the kit with all the rods and jets to play with them. more important was in those days i was limber enough to crawl into a truck engine compartment, do a quick clean and put the truck back on the road in minutes. happy customers and good money.

Pontiac didn't have the heat sink problem. Their engine design used a valley plate and air gap intake manifold

It's the thinking man's carburetor.

Tony there was a redesign on the Quadrajet somewhere around 1971. If I remember right they did make the fuel bowl slightly larger, and the carb is slightly shorter than the earlier ones, but the bowl is still too damn small. I actually run one on my big block olds in my Trans Am and the trick is to use the Pontiac style fuel filter housing because it's longer than all the other's, use no filter (so the bowl becomes that much larger), then use an inline fuel filter, with the Holley electric pump in the back. My car stopped nosing over as soon as I did that. Also no one discusses it but you could adjust the secondary air door, that's usually why they bog people don't know how to set it. I tried to replace mine with one of the Holley spread bores, and the primary throttle response was nowhere near as good, it did pull better though when the secondars opened up.

Autolite (Ford) also had a spread bore "quadrajet-like" spread bore, center bowl carb. It was mostly known for its use on the standard use 429 / 460 engines and called a 4300 series. The basis for the Summit (and earlier Holley design) is the Autolite 4100 series used on the early and mid 60's Fords like the HP289's, 352 police models and the 390GT Fairlanes.

That unmistakable.. “DouuuWaaaa”on my pops 73 LeSabre allowed me to fit in with the street talk when the “Quadra-BoG “ got mentioned🤘🏼⛽️

Your viewers don't seem to understand that the goals of the car companies were different from our goals. The car companies wanted good, reliable and efficient carbs that could be used across multiple applications. The ability to cheaply and quickly mass manufacture items also played and plays probably the single biggest goal of any item they either produce themselves or buy. Plus, they all had to work well across wildly variable conditions. Lots of people live at elevation and buy gas at a different elevation. Lots of people regularly see 100 degrees and a lot of other people regularly see 0F. Every part on a car, whether it's the carb or the alternator or the leaf spring is just a giant set of compromises. All this stuff has to work seamlessly in a very wide variety of uses. Just think of the pick-up truck. These things have to drive and ride well whether there are thousands of pounds on the bed of it's empty.

My memory on the quadrajet was on stock GM cars and trucks back in the day. Back then with gas blends they worked great.

Nunzio Romano of Pontiac fame said it the best, "Rochester doesn't have to advertise, they sell 5 million carburetors a year". The "problem" with Quadrajets are the "mechanics" who attempt to "fix" them. Nothing more.

Secondaries that go BAWAAAAAHH!!!!!!!!! Brought to you by GM 😉👍

I had a 75 chevy monza town coupe with a built (At that time)350 engine!! Had several issues with my Eldo carb 😂 my dad knew a lot about the Quadrajet carbs he rebuilt one for me on his kitchen table I will never forget it 😂 I put it on the next day with his help that damn car ran so damn good and hard for several years after that and never had an issue!!

I owned a '71 Pontiac T/A for a number of years in the late 70's early 80's, that had an 800 cfm version of the QJet. I sent away for an H.O Racing QJet rebuild and tune kit, for the car. Rebuilt it, sealed the well plugs, installed the tuning parts and performed adjustments according to the instructions that came with the kit. It, along with a distributor recurve kit, made a very noticeable difference in the seat of the pants response and performance.

I got a completely rebuilt quadrachoke online for about 250$ it was professionally rebuilt like new, for my 1977 chevy 454, runs like a clock after rebuild.

My buddy had a 455 pontiac and tried all kinds of carbs on that motor, everything made less horsepower and torque, that motor just loved that quad

i am 67 years old and a retired professional transmission rebuilder and old hot rodder. growing up my dad had used car lots. he had an old mechanic that was the real deal hot rodder in the 60s on, he told me his favorite carb was a holly 3 barrel. he ran small block fords,,,,,,,,,,,,,,,,,,

Q Jet is reliable, works on hills, gets good mpg, good throttle response for a carb, and you can't beat the sound and feeling when the secondaries kick in

I admit, I grew up tinkering with Rochesters and love them because I KNOW their kinks and quirks! I know it is blasphemy, but I have never gotten the hang of the Edelbrock. I do enjoy the Holley for SOME applications. Thank you for this! Now we can compare Bing vs. Mikuni bike carbs!

The Thermoquad came out in the aftermarket as a performance replacement for the Quadrajet in 1969. The aftermarket Thermoquads had pressed-in jets, with o-rings and grooves. Chrysler didn't trust the o-rings to not shrink and requested standard screw-in jets in their factory installed Thermoquads. The Quadrajets made for Ford 429 Cobra Jets have the air filter stud extend all the way down to the base plates and threading into the baseplate, at the request of Ford, because was concerned about warping if the air filter stud was over tightened. I see the Carter Quadrajets mostly on Chevy and GM pickups, maybe vans. In the early years of the Quadrajet, there weren't enough for the Chevy applications and some 1965 to 1967 396 engines have small Holley's on them. The 1965 396 was supposed to have a Quadrajet, but due to the supply shortage, many 1965 396's got Holley carbs. In 1966 and 1967 the cast iron Holley intake and carb was used on some high performance 396 engines,

*But what about the electronic QuadraJet/DualJet…E4ME/E2ME, etc.? You’re slackin’ Uncle T!*

Q-jets, my favorite old school carb. I have some 70's era in boxes now. If or when I need one I have some. Just like the TH350 and TH400.

I sold a 77 Corvette a few years ago that I had for 13 years or so and it sat nearly the entire time with old low grade modern gas in it (meaning the carb. had dried out gas and sat too). When I decided to sell it I rigged up a gravity fuel supply straight to the carb (removed the onboard fuel filter) and after prep. oiling up the engine and putting in a battery I primed the carb., turned the key and it started and ran nearly perfect. I had to keep blowing into the little gas can to pressurize it and get fuel past the needle valve in the carb. Point is that this Quadrajet, original to the car (I'd guess it was rebuilt at some point though before I got it), worked nearly perfect. I really like the spread bore design of those old carbs.

Once understood, the Quadrajet is tough to beat..I once modified these..my favorite thing was to install a Pontiac Ram Air float..it's smaller and allows more fuel in the bowl..

Theres a reason why your local parts store no longer has direct drive radiator fans hanging on the wall for sale, but they still sell spread to square bore adapter plates for cheap. I've never had one that didn't give trouble

The single most versatile, tolerant, adjustable, dependable carb if all time-. especially the ones with the ported vacuum advance line fitting. No stupid transfer tubes; no stupid power valve. Just more adjustability than a 4 valve v8 with a roller cam😉

I have a 455 Buick Century GS that came to me with a rebuilt engine, headers, bigger cam, Edelbrock intake and Edelbrock 750 CFM carb. I had trouble with vapor lock on the Edelbrock,and had trouble getting a consistent idle. I pulled it off and discovered that the Edelbrock for Buick Intake was full SPREADBORE to fit a Quadrajet. It had an adapter plate to the square bore fitting. When I removed it you could see it was cutting off about 1/3 of the secondary flow if not more. I sourced a rebuilt Q-jet and no more vapor lock, smoother more controllable idle, an goes like a wild fricking Banshee now. Pretty sure I improved 20 plus HP. I LOVE QJets!

8:50 to get more flow without increased pressure it seems like the Quadrajet guys would have run fuel pumps in parallel, not in series.

Bigger fuel bowls are only a band aid for an insufficient fuel system. The needle and seat will let more fuel into the carb than the jets let into the engine so that means you’re just extending the amount of time until it runs dry by putting a carb with bigger bowls. This is what we would refer to as “treating the symptom and not the disease”.

When I was about 5 back in the '60s my dad (RIP) gave me a spare 4bbl he had lying around to play with. I took it apart and put it back together. I remember having like three screws left over. 😁 In high school in the late '70s my gearhead classmates almost universally dismissed Qjets, calling them "Quadra-Bogs." I didn't know enough either way to say, and though I read Hot Rod fairly regularly at the time, I don't recall it shedding much light on whether or not Qjets were good. Great video -- very illuminating.

I bought a 80 Malibu in 97 when I got out of high school , it had a nicely hopped up 355 with a big comp cam, roller rockers , nice valves and springs. It had a worked quadrajet said the guy I bought it from. And for what it was it was a bullet! I pulled the quad thinking an Edelbrock carb would be an upgrade, nope ! It was noticeable how much it slowed down. Spent 2 days trying to tune it to the quads performance, never happened. I put the quad back on and was happy again .

Tony is right about their efficiency. At the end of the carburetor era, GM stopped using the usual crop of 2-bbl carbs. Instead, they bolted a so-called Dual Jet, which was a Qjet with no secondaries in it, onto their 4 bbl manifolds. And there is no substitute whatsoever for the sound a Qjet makes when the secondaries open. You never have to guess if they are functioning or not.

I personally like the oh ya here a little more info at the end.

I had Quadra-jets on a couple of GM Cars and Trucks back in the 70's. I LOVE them! Love your content and including us other guys. Thanks!

Appreciate the open mind to this stuff, everything has its use along with its pros and cons.

Best street/strip carb ever devised. I was always a Ford guy, but ran them on all my cars. Back in the 70’s, I was running a 67 Mustang that I’d swapped a 70 351C 4bbl. Initially ran a Holley 780. Great race carb! Swapped a Q-Jet and lost nothing at the strip, gained 3 mpg in daily driving & better, off-idle and midrange response. Helped that I lived in Rochester NY, and knew some really good tuners! True, about heat soak and small bowl. I ran a line cooler at the strip. Never starved for fuel, however (8th mile track). But I have out-run the fuel pump on my boat (350 SBC). That Holley/Autolite 4100 was an excellent carb. I ran one (4011 spreadbore) on a 350 SBC and a Ford 351C. Never had an issue with it! Not quite as tunable as a Q-Jet, but incredibly reliable! (Like the Autolite 4100 that it cloned).

One more step up from here. Thermoquad. 😂 Oh, you included that later in the discussion.

My dad had a 72 chevy blazer that he ler me drive a lot in the late 70's and it had a 307 with a qjet in it. Ok so i could never spin the big 4x4 tires but when i wanted to pass anybody it had what i thought was awesome passing speed.

you're earned my respect in this video. good understanding of the kwodjet, love these carbs they run on a 45. my holley almost does that...

I have used the summit 750 that you're referring to it actually works pretty good The only thing I don't like about it is kind of cheaply built it's probably why the price is low , also I've heard The Carter built quadrajets are the better ones , a few years ago or maybe more now I sent a Carter quadra jet to jet performance chip in California with a spec sheet of my vehicle and they rebuilt and custom tuned it for me for $300 I couldn't be happier with it..

Oh Unk. This series is SO good. I've long wanted this knowledge.

Even dodge used the Q-jet my 85 ram w350 with the LA 360 has one on it. Hasn't given me any trouble in years in any weather cold or hot.

The most problems I have had with a carburetor platform overall was the Quadrajet. The least problematic was the Ford Motorcraft 2bbl. They are easy to work on and clean and get running after sitting for a long time. Usually the only thing you have to do to them is change the accelerator pump every once and a while and they're good to go

Great video Tony! I had a quadra jet on my 69 Camaro. Between that carb and the 265 gears the car had it got great economy and drivability. I have a friend with a 67 cutlass that’s into drag and drive events that has run 10.0 sec 1/4 miles with the Q jet! He definitely has some tricks with fuel delivery including a surge tank but it is doable.

I put a edelbrock performer and a holley 600 on my chevy 305 and I'm so happy I could shit.

I sure hope this dude is making the money he deserves

Rebuilt one for my 68 olds tornado. Ran like a watch.

Well done sir! I really like the cool stuff you called trivia. Very cool video!

The beauty of the Quadrajet was that they always ran well with no special maintenance right from the factory. Increasing performance was as easy as removing a small vacuum linkage rod that inhibited opening the secondaries. The power came on with a bang!

Very well stated and informational...never would have guessed some vettes have Carter built quadrajets....thanks boss!

I ran the 750 avs on my 340 Dart, worked great!

I've got the Carter Quadrajet in my 79 Chevy. I was curious about that. Thank you Uncle Tony!

I had a 4100 on a 289. It worked very well. You could set it up & forget about it.

Tony, check out an episode of Engine Masters where they tested several carburetors from Summit Racing straight out of the box on a dyno. Your summit carburetor version blew them all away for AF ratio, and power to if I remember correctly.

I had a Holley branded 4100 with vacuum secondaries. was always super happy with it. s still have it on my shelf.

You're right about the Rochester and fuel efficiency. I went to a Pontiac Oakland convention that was about 250 miles away. I drove my 1965 GTO 389ci Tri-Power and was shocked at my fuel mileage at 55 mph. The car had a Muncy M22 Close Ratio and 3.90 rear gears. I got 19 mpg running up the Interstate to the convention and back. A friend was working at a Chevrolet dealer at the time and he took his demo, a 1981 350 ci Z/28 on the same route and speeds and only got 17 mpg. Those unfamiliar with the Pontiac Tri-Power set up in 1965 the center 2bbl was smaller than the other two outboard carburetors. In 1966 Pontiac increased the CFM of the center carburetor from what I can tell about 50 CFM.

I’ve ran HOLLEY-4100 style carb for 30 years! Milled the choke horn, Fast jet changes / no bowl draining ! Jets go straight into the bottom of the bowl. uses all performance carb parts ❤❤

Love your channel and it's good to see a young guy keeping the faith. I had just about all those carbs and most of them work well for what they were designed for. As for the Q-Jet they really are excellent for everyday and mild performance cars. Personally, if I had to choose my favorite (for everyday) it would be the Ford 4100 a really excellent carburetor.

As an old chevy guy I know and like quadrajet carburetors. I was about to rebuild a 1985 Quadrajet off my Square Body but am intrigued by the Summit M2800 carbs. Looking forward to your upcoming video about them.

My 65 Mustang 289 came with a 2bbl stock. When I sold my 67 Mustang 289, took off the Carter AFB and swapped it into the 65 to keep it. Loved that carb.

You can do it anywhere, your knowledge is really grateful, l love the Quad, those secondarys😊

Ya the Thermoquad is my favourite for a Daly Street performance car get the best all the carbs in one and they look bad ass on a engine cleaned up and can’t beat that sound when you stomp it. And they get great fuel economy, if you just run it on the primaries.

It's nice to see you Tony to bring this up. The overturning off chevron difference allows us to brig the the unelected back into check.

check out the OLDS 455 on the dyno at NICKS GARAGE and see how the Q JET faired at the end!

I loved the qjet in my 86 el camino..but looking back after seeing this i shouldn't have. This explains everything i was having issues with.

Great videos Tony... fellow car guy up here in New Brunswick Canada

nick had a 455 olds that was a mild build on the dyno he kept switching 4150s up from a 750-800 then 850 where he maxed the 455 out at about 480hp IIRC. then the owner showed up with the q-jet that came with the motor a 750cfm --slapped it on there and the big olds actually picked up a little torque and dropped just a few HP --somthing like 470hp and 500 ft lbs tq-- from the smaller q jet. i'm pretty sure the qjet had been warmed up a bit sometime..

With all you said about the Q-jet, which is true, the biggest problem I ever had with a Q-jet was the primary throttle shaft wearing out the base plate. Yes, most of my Q-jets were over 20 years old when I received them.

I didn’t know all that, nice history lesson. My quadrajet clogged up recently, it had run flawlessly for twenty some years. It is not going to clean out, needs a complete tear down alcohol appears to have introduced moisture, grime, sludge and clogging. Will rebuild it but my shop is crazy busy so I plan to roll the dice on a cheap temporary knock off to bolt on. I don’t like my cars non running and sitting for months, so if it gets me through summer and it later becomes relegated to a good working spare, it was worth it. I have some other old carbs of unknown condition of all different makes that maybe another someday will get around to rebuilding as well. That’s my shop right this minute, a shop with dozens of gummed up old carburetors and not one known good working spare. Nice job on the video, I don’t care if you forgot anything until later. Oh and the hardest problem I ever had on a carb was a thermoquad on one of the 400’s I ran in my drag car that had a bog in it when the secondaries kicked in. Only my own stubbornness kept me from smashing it and tossing it in the scrap bin. I did get it figured out perfectly but that one had my blood boiling and my patience tested to the max. I don’t think I was ever quite the same after that one. I used to love rebuilding them, now I will but I would rather do or fix something else.

I used to race circle dirt stock cars.in the 90's the quadrajet were well know for the best stock circle track carb due to the center hung floats. Was always able to keep up with fuel demand. Only seen a heat soak problem during caution flags after a hard run

I was looking at the 4100 yesterday and I agree its gotta be the most practical overall design for today and those Summit ones look very well set up in terms of hardware

I’ve got a 1972 HQ Holden Monaro (GM) 308 factory Q-jet, had it rebuilt 15? years ago… Runs excellent👌

Yep. I had an 87 B350 Dodge van that had a Rochester Quadrajet on it. I took it of and put a Thermoquad on it and got better gas mileage.

I built a QJ from 4 carbs, boy that thing ran really good on a 307. Truck started every time, even on hot days and with the engine hot, and it still took off. We have an EB, well two and had to rebuild them a year later!

Yep, I used cooly cans a lot back then. That was the (hot set up) for hot humid summer nights. Cruising & at the strip. Some guys even packed dry ice around them. Wouldn't do carbs today because of the fuel we have. The 4 bbl Autolite was on my 77 460 Merc 2 door Merquise. Worked great.

I have had the Holley, Edelbrock, Thermoquad and The Jet. Holley was always my favorite and gave me the best results.

The Quadrajet was a very GM-like design, it's two sizes were found on engines from 250 to 500 cubic inches, really good drivability and reasonable fuel mileage if you kept your foot out of it. I had a 1964 Ford with an Autolite 4100 equipped 390, great car, great carburetor.

7:00 absolutely true, the E10 and E15 fuels with ethanol blended in are great for two things, one is subsidizing farmers, the other is keeping you from enjoying your vehicle when the ambient goes over the mid 90s. This ALSO carried over to EFI vehicles. Now I'm not a fluid dynamics engineer, but when the temperature goes over 95 degrees and my wife's Explorer starts surging and stalling, I believe it's vapor lock from boiling fuel in the fuel rails. I believe it because the fuel pressure sensor located on the fuel rail gives an out of range reading on my little scanner and it sets a CEL code. If we run the 100% gas we're lucky to have available here in Oklahoma, it doesn't do that at all. It could ALSO be that the EGR tube is plugged up and all that extra exhaust heat has nowhere to go except around the intake to heat up those fuel rails. After I change out the EGR valve and tube I'll retest. For the rest of my anecdotal evidence, I've seen the temp go up to 106 so far this year and in the days following putting in ethanol free 87, it runs fine, while in the days following filling up with normal 87 it'll be surging and stalling by mid afternoon. I've also tried a couple tanks of the Casey's ethanol free 91 premium because it's the same price as the ethanol free 87 at many other stations around. I can't feel a noticeable difference between the 100% 87 and the 100% 91, but any of the E10 and E15 fuels just don't make the truck happy. Hot weather drivability isn't always something you can tune around, sometimes you actually need to use a different fuel. If I had anything with a carburetor (and I am looking), I'd be using the ethanol free fuel no matter what.

Great video brother right on!😊