The only reason it makes that noise is because it has big secondaries and it is all vacuum when they open up I absolutely hate quadrajunks. They're almost as bad as the Carter thermoquad.
The Rochester QuadraJet is the greatest carb ever made. The fact that I'm a lifelong resident of Rochester and live maybe 10 miles from where they were made has nothing...NOTHING...to do with it 🤣
I was born in the same small town as Larry Bird.you can't tell me he was'nt the greatest man to touch the leather of a basketball so I completely understand where you're coming from! 😆
Living in Rochester and hot rodding peoples cars you hsd to know the cure for the Quadra jet bog. Take the top off and remove the internal parts look at where you can remove part of the wsll inside of the carb to hold more gas and eliminate the bog . FORD used those carbs on the 429 CJ and Boss 351 without any problems and those original carbs are worth real big bucks .
They were easy to clean the jets, too. I simply pinched the fuel line to drain the float bowl while it was running. Shut it down, and then take the spray can of carb cleaner and fill the float bowl with it. Run it until the bowl was empty again. Let the fuel line go, and they would run like a top!
my buddy had 85 monte carlo SS and yes I know it did not have lot horsepower compare to today cars but when the four barrel open is when the magic happened. Brings back great memories of late 80's . Thanks
I had 84 and 88 SS's bucket seats but my buddy had an 88 SS with a bench seat and colomn shift and man I loved that bench seat. I've looked for another SS with a bench but they must be rare. Love Qjets never understood why people hated them. That baawaaa sound was awesome to hear. I just traded for a couple and one bop.
Worked at a cad/ olds dealership had an old mechanic that replaced several a week! I snagged everyone I could pulled apart, had all sizes of jets, metering rods primary and sec. Different power valve springs ! Loved the carb in a 350 I built in a 3/4 ton pickup never a bog or stumble start to a pegged speedo. Lot of part switching at first but boy did it work great. Thanks Tony. God Bless.
My 86 GMC came with a 4.3 V6 , 3 speed on the column and non electronic Qjet. Switched the engine/trans to a 350/350 , then a Vortec 305/350th. All I've done to the Qjet is to rebuild and replace the throttle shaft bushings. I've always said- Qjet for every day driving/fuel mileage and a Holley for performance.
@@eddieb4227 i know huh I mean we didn’t have a ton of cash as teenagers and the parts were everywhere. Besides the junkyard more than made up the difference in overcharging on other parts
I think most of people hating ran bad gas through them. Or had a square borentake they bought. It doesn't require much to go fast back in the day open Element air cleaner headers and a napa cam although the days I seen that stuff was the '80s don't sleep on the 305 you can catch some mid 14s with a good gear. On the peg leg too!
Well it's just like the Carter Thermo bog if you don't know how to set it right or watch out for that plastic float breaking it's going to give you nothing but trouble
@@truckerkevthepaidtourist ThermoQuad float issues? I tried & tried but the dipstick in my freshly rebuilt 340 always smelled like gas, and the highway mileage with it was appalling (3.55 posi rear end)
To think the quadrajet has been “out” of production longer than its entire run of 21 years lol… man time flys! Still the best street carb.. especially when it comes to weather up in Canada where I’m from.. still use a edelbrock rpm 1910 quadrajet on my big block 67 Chevelle, got sick of sticking floats, crappy gas mileage in the Holley’s not to mention the constant tuning whenever the temp started changing!
Actually he slightly erred. The Q-jet was first introduced in 1965 for the big block Chevys, and went out of production with the end of the 1990 model year Olds 307 engines.
Noting how most drive, a typical square bore 4 barrel sees something odd regarding street use: the 40-60% throttle range is darn near a dead band: people are either cruising or passing. The q-jet pretty near eliminates that regarding primaries.
My buddy used to rebuild these for fun. He would buy them from salvage yards and rebuild them, then put them on his shelf. His dad taught him the tricks to them. He put them on all of his vehicles. My favorite ones were on his 455 Buick, and 455 olds. The sound they made was awesome. Sounded like the hood was going to be sucked into the motor. The memories of that sound as he rolled past 5.0 mustangs with his 850 cfm sounding off will always be with me. I always considered them to be the 1911 of the carburators. To many parts for the average Joe to break down and rebuild, but incredible anyway..
I have a 66 toro with a 69 455 that has been tweeked here and there. The rice burners get spanked bad! Wish I had kept the 66 trans since it had 3.21 gears Compared to the 3.01's of the 69.
Tony: On February 15, 1967 my father took delivery of new Pontiac Catalina. Stalling issues were addressed by Allison Pontiac, RIP, with the warning not to use "Shell" gasoline. The problem, as you indicated, faded away. Thanks, for the trip down memory lane.
As a life long fan of the Q jet I must confess my sins here. I have plugged those two holes that Tony mentioned with Bazooka joe bubble gum. I was just trying to get back on the road and drove on that carb for 5 or 6 months before selling the car. 2 owners later it got a Holley because that kid thought it was an upgrade. I should have bought that Q jet back.
Having fixed a shattered transmission shift linkage in a GLH Turbo using nothing more than a long shoelace - and then not installing the new shift rods for 2 years because I'm a lazy bum - I salute your field expedient repair work. Sometimes you just gotta go with what you know.
I started working on cars at a GM dealership right out of high school in 1995. We used to rebuild these all the time. They were still very common on the road in the mid 90’s. I would say at least one a week average. The well plugs were VERY common issue we seen.
I have one in my 87 El Camino, a California-compliant one. It’s currently hemorrhaging gas, do you know if they are an expensive fix, like more expensive than a regular one. I think I remember being told it was computer controlled.
@@BigCaucasoid I honestly don’t know how much they cost to rebuild nowadays. Yes yours I’m sure has a TPS sensor and a metering rod solenoid. It has been soooo long since I’ve even seen one of these carbs.
Most regular car guys that didn't have a muscle car had these quadrajets. Other than that choked out two barrels from the '70s man they weren't super impressive but for the day if you snatch it down first and it sings it's song much more impressive than the 301 Pontiac 2 barrel your friend had hell glass packs off the y-pipe for effect cause you bought the car for $500 and you can bragged your friend it goes 45 in 1st cause it had 256 malaise gears!
The adjustability and the ease of maintenance on the QJ are its strong points.... along with great part throttle fuel atomization. As stated, the fuel bowl area leaves a lot to be desired, but on a small-cubic inch V8, these things were amazing. Lots of torque, great throttle response and, when the urge to pass somebody hit your right foot, they got up and flew. Great review!
great for a DD, riser setup helps AND isolates from intake manifold heat. its always been an easy inexpensive kit. more air flow under the air cleaner with the carburetor and fuel line an inch higher, common sense simple.
I am an off road guy. What I can tell you is the Q jet is hands down the best off road carb out there. The reason it works so well is the exact reason UTG cites as a disadvantage. That is, it's small float bowl. When you are off throttle, even a small amount of gas spilling into the manifold would kill the engine. Off camber would starve the engine. Imagine moving down a steep, ruff incline at idle. With a Holly and it's comparatively gianormus float bowls gas can just spill through the main jets, put the fire out in a heartbeat. On throttle on woops you could hear the engine sputter and the tell-tale puff of black smoke. Holly recognized the problem and made accessories, which I dutifully installed, but never really solved the problem. Power brakes and steering are compromised at the worst possible moment. I rolled my jeep onto its roof and my Q-Jet was STILL RUNNING. I actually had to reach up and turn off the ignition. Loved the Q-Jet, next best thing to Fuel Injection, which is what I have now.
@@heavymetalmadness666 Apparently you didn't read my post. My 4X4s are all equipped with FI now. I've been off roading since the seventies, before fuel injection was even a thing. Here's a little advice that you didn't ask for, you're better off to stay silent and be thought a fool rather than open your mouth and remove all doubt. Oh, and another thing, I learned back in the sixties. Back then, they actually taught kids stuff in school. For example, I learned the difference between you're and your, you should look into it.
I had one off a Cadillac 500 on my 11 to 1 purple cam 440. Ran awesome excellent throttle response and gobs of power. No adjustments just bolted it on.
The QuadraJet is without a doubt an excellent carb. They do make strip kits for them, and the fuel delivery issue as a result of the incredibly small bowl can be helped by what you mentioned; different size/shape floats, bowl contouring, as well as larger orifice seats, and windowed seats. I ran deep 11s with a 69 Nova street car, very mild pump gas 454 and a 4-speed, with a HV pump, and a larger/windowed needle/seat. Never nosed over once, and was as responsive as EFI I also have over 2 dozen Thermoquads in my “collection”, most of them being the early 6xxx series, and two aftermarket SuperQuads. All are excellent carbs. 👍
I had boxes of these years ago, I learned a lot of the tricks to them and with several tweaks and small modifications I had very good results from them. The most misunderstood thing was one you learned how to work with them, they remained set, whereas Holleys you had to fart with anytime the conditions changed. They could actually be very hot carbs once you figured them out.
Back in my days of wheelin trucks, the QJ was the ONLY carb that wouldn't flood out in nasty off camber situations. The right would have to be almost on it's side to flood the QJ.
My 85 Elcamino at one point had the HO intake and Quadrajet pack. It wasn’t anything too hot, but was definitely more fun then most daily’s. I found a cheap edelbrock 650, rejected it to match and it was great. Much more lower end and a nice response all the through. It was a little more thirsty then before but that was obvious and didn’t matter much. Then I made 3x my money back selling that one, bought a new proper sized Holly. It took a lot longer to find the sweet spot between everything, felt similar to the edelbrock de tuned, and was just a little better on fuel. But once I got familiar with tuning it, it became second nature. Although anytime I would be driving through states, to the ocean, or over about 1,500 feet from last mixture adjustment I would always end up tweaking it at the fuel station or pretty view. It the time I didn’t mind it al all. Getting under Emily’s bonnet was never a bad thing.
@fivestar8337 Make sure the plugs in the bottom are properly sealed, float settings, and a big one is increasing the spring pressure on the rear butterflies to eliminate the bog. (I don't remember specifics. It's been 40 years ago).
Quadrajet is poor man's fuel injection. My K5s love them! I was stuck in a hole at 45°, and the quadrajet didn't miss a lick for an hour until I got the winch to reach something that would hold.
One of the things that separates the Q-jet from other carbs is the off-idle circuit. All other carbs only have idle, main, and four barrel. The Q-jet offers a fourth circuit...idle, off idle, main, and four barrel. Another known problem that old Q-jets have is worn throttle shaft. A worn throttle shaft causes vacuum leaks, and the throttle primaries to hang up.
"All other carbs only have idle, main, and four barrel." Ignoring the "four barrel" part, what you're claiming is that all other carbs only have idle and main. That's not correct. Others have an "off idle" circuit as well, the Dellorto DLRA being one of them. In fact, the DLRA off-idle circuit has its own jet, so the carb can be tuned for idle with the mixture screw, off-idle with the idle jet, and main with the main jet and an "air correction" jet (an air bleed).
Thermoquads have an off-idle circuit as well. A couple years ago my 72 Charger developed an off idle stumble, turned out the jets used for the transition were not getting fuel.
@@ShawnD1027 As soon as you saw my post you probably did two hours of research to find some obscure brand of carburetor that had an off-idle circuit just so you could say I was wrong.
Rebuilt hundreds of " Quadrajunks " during my 49 year wrench career . About their only real problem was often overlooked - the wallowed out primary shaft hole in the throttle plate creating huge vacuum loss . Aftermarket bushings were a simple fix .
Also the secondary air valves sticking because the top plate has been bent due to overtightening. Creating that Quadrajet 'bog' when the secondaries open.
My 1973 Pontiac 400 had a phenolic spacer under the carby and never had vapor lock. The Quadrajet is the center of the famous story of the Pontiac that hated vanilla ice cream. A classic.
Tony I'm a huge Q jet fan. I love the way they drive on the street, the sound they make when they're floored, and the snap off the line those tiny pimarys create. Have you ever read Cliff Ruggles book it's actually really good about getting quadrajets set up for high performance. One thing that really worked for me was adding an electric fuel pump because the mechanical pump couldn't keep the bowl full at wide open throttle. Also Victor Reinz makes a thick gasket that actually helps keep a little bit of heat out of the carburetor. And they're actually application specific because I think there's two different gaskets for Quadra Jets and it has something to do with the little notch on the primaries. Also they redesigned the Quadrajet in like 71 or 72 when they went to that shorter Quadrajet. I wonder if that was something to try to fix all the vapor lock issues you were talking about. I don't know why but I could never get the Holley Spread Bores to feel as good as the real Q Jet they were always very soft off the line.
I had an issue with a big cam 455 pontiac sucking the bowl dry at highway speeds it would start stuttering and starving for gas, let off a bit and it was fine lol......I ran bigger diameter lines, a larger fuel filter instead of the small one in the carb and a high volume mechanical pump and it was ok after that. Cliff's book is terriffic.
I bought a 68 GTO in 1976 & as a young man thought I was doing a good thing by replacing my stock Q jet with the New Big & Bad Holly spread bore.... The Holly started to act up with in a year I Rebuilt it 2x with no results so I put the Q Jet back on & it has been working fine to this day...!!! I still have my Goat...😊😊
I've rebuilt a Qjet with the wrong rebuild kit because the parts store didn't have the correct one and it worked. I've broke down and sprayed one down in carb cleaner and starting fluid in a 1966 Olds 98 and limped it 30 miles home. Nothing wrong with it on a driver.
I used to love it after a rebuild when the owner drove it for the first time…I’d set it up so the secondaries and the downshift hit at the same time. A strong stock engine could bark the tires. Saw a LOT of really wide eyes!
There were a few quadrajets in 1965, they were on most GM four barrel engines in 1966.The last was a 1990 Olds 307. Carter also made some quadrajets for GM. They look identical to the Rochester.
Indeed carter made quadrajet carbs as well. My 1973 impala had a stock 350 with factory dual exhaust and a CARTER quadrajet. Great running car. Miss that car.
in late 70s had a Qjet on my 455 olds motor, never bogged off the line ever, when it hit the secondaries would literally smack the top flaps wide open instantly, GREAT CARB
My father built his shop, business, and reputation on that Q-Jet right there. He did them all, but that was his bread and butter. But the vast majority of all of them where for people just wanting to go down the road. Drivers not Racers. As for the Secondary Metering Well Plugs... that was dad's secret weapon for success in all that. We bought the factory Re-Build Kit for them, with the O-Rings (QJT-1 & QJT-2 part numbers if I remember right). Drill them out and pop in those plugs and they run forever. We used to buy them by the case, and still have about a half a case of them left over...... I think it was a $2 part and only took a couple minutes to install. One of these days (now that dad has fully retired) I'll get video of him installing them 1 last time. Good Video as always UTG!
I have a 1972 C10 Pickup which had its original 350 engine with the QJet 4bbl carb. Over the last few years a knowledgeable friend who has built many Chevy engines built a 30 over 400 small block for me which will has about 325/350 HP and 400/425 ft lbs of torque. When starting the build I asked if we should get a Edelbrock carb, as the QJet has 91000 miles, for the new engine and he said no reason as the QJet is all we need and he was going to rebuild it which he did. He said people do not understand them and they are a great carb. My engine and the rebuilt QJet are working well together.
The best street driving carbs i've ever owned were, and still are, quadrajets. One of mine has developed the well plug issue. a few years ago it was very slow and would only leak out over the course of a few days. Now it leaks down in less than a few hours. Need to pull it off and fix it. I should probably send it off and have it rebuild because it's leaking air through the throttle shaft. Guess even the great quadrajet isn't susceptible to age with this example being 43 years old without ever being rebuilt. I think a large contribution to their lack of prevalence in performance applications, in addition to bowl size, is the lack of quick tunability. Where on a holly you can change jets, power valves, float heights, etc. quickly and easily making tuning far easier for the aplication.
You can reduce/eliminate throttle shaft wear by moving throttle return spring anchor point to the front of the intake manifold instead of under the throttle cable/linkage. When it is under the linkage, BOTH components are pulling in the same direction, thereby loading the back half of the throttle shaft bore.
@@wesalker3479 I'll look into that if/when I either have this one rebuilt or replaced. It's not very high up on the priorities list at the moment, unfortunately.
I agree, it was also one of the last carburetors that was able to meet emissions before EFI took over. The triple booster primary gave a nice crisp response on the primaries without trying to get ‘just right’ pump shot. Great throttle feel. I design production EFI systems now, they’re far more accurate than any carb ever was (I get A/F ratio errors smaller than 0.01% across the whole operating range, including transients), but the Q-jet really was the closest you could get mechanically.
You are absolutely correct Tony: Q-Jet fuel bowl is small. How do i compensate for that? Run Z-28 / Corvette / High Capacity fuel pump, remove internal fuel filter and run in-line filter. Change the tucked fuel line from pump to carb, (has too many bends) and run the line in a straighter fashion, away from the engine and insulate it. You are again correct when you say you can get away with it if your fuel delivery is top shape. Thank you, Keep up the good work. Pierre Lafontaine
The tiny, centrally located bowl is actually a pro when it comes to off-roading, and off-roaders still love it when they don’t have EFI. The Q-jet can operate at angles that would make most other carbs lean out on one side and drown on the other. I’m a bit ashamed that I’ve never a run a Q-jet on one of my own cars . I’ve got probably a dozen Thermoquads, though, and I really, really love those. We all know the weak spots of that one, but when it’s not abused with over-torqued bolts and incorrect jet well O-rings, it works wonders.
Remember the singer Lou Gramm of Foreigner raced the streets of Rochester and sang about Lake Avenue street racing . Could he have been a Quadra Jet user ? .I know his brother Dickie had a quick GS Buick with one .
My camaro had an electronic Q-Jet from the factory. What an absolute pile. I swapped it with an earlier model. Picked up a book with tips and tricks for Q-jets, and proceeded to create the best running street carb I’ve ever owned. Since moved to Holley’s for performance, but still love a well tuned Q-Jet
My 1987 Cadillac brougham 4 barrel quad Rochester cab is racing with my foot off the peddle it is still racing down the street even in park it is still racing
As an old guy coming back to a classic car, this was a terrific breakdown of the Quad-J. It was clear, simple and to-the-point, I have subscribed to your channel and look forward to digging into all of your tutorials, thanks Brother!! (currently resto-modding a '68 Impala Custom Coupe, wish me luck :D))
Lovingly known as the quadrabog . If people would read a little on how to adjust them they actually flow 750cfm and I have absolutely never seen one that wouldn't run even sitting for 20 years or more . Fuel economy and hp all in 1 carb
Being a young 20 year old car freak myself, it's so nice to see some love for this carburetor, the quadrajet and thermoquad will always be my 2 favorite carbs just because of that sound. The sheer tunability of the Q-Jet puts any fancy holley to shame, I've been wanting to get myself a small car to swap a 350 into with this carb
Best street carb ever.. has a g body cutty 350 Chevy with a quad...I was once wanted by the police and was identified by the sound of the 4 barrels cracking open, you could hear the gas flow dumping.. duuuuwwhoooppppp duuuuuwhoooppppp
It is and he unravels the mystery. I had a 73 stepside and after a few rebuilds over 300000 miles I never had vapor lock issues. I installed an Edelbrock Performer manifold so maybe aluminum behaves differently. The correct rods on the secondaries and setting the air door spring made a big difference. I was just under 300 HP, so definitely not "high performance", but it served me very well. The ultimate "set it and forget it" carb. They don't need constant tweaking to keep their tune.
@@kennywhiddon1497 Yes the Olds 442 in 66 and 67 cleaned up in C/Stock. It wasn’t until the Ford FE 428CJ that anything else would beat it. 1 race Shelby Mustang fastback in 67 ran the KR8 that was a 428 CJ that gave Olds any grief. In 68 Olds ruined the 400 by putting the 4.25 stroke in and reduced the bore to get 400. The best in 65-67 were the Olds OA1 400, a 7000 rpm screamer, the Pontiac 400 Ram Air 3 and 4 , the 375 hp 396 Chevelle and the Buick Stg1. Until Ford got their 428CJ Mustang fastback, they Ruled. The KR8 428 wasn’t allowed to run but one race. I still have my 394 ci FE with a Holley now, but when I had the Qjet on it after the modifications and an electric pump with AN-08 line and a deadhead regulator at 7 lbs I would wind it to 7000 +, and even now with the 3310 750 a friend of mine put a jet block on in place of the plate, it will do 7000+ but no quick getting there than the 850 Buick Stg1 carb..
My personal experience with carburetors has been mostly with the Quadrajet. Once I leaned how all the systems worked I found it to be the most tunable carburetor and I was always happy with the results. Easy starting, Smooth running engine throughout the RPM range and really good fuel economy. Yes it has it's issues but they all do. Electronic fuel injection has really put most carburetors out to pasture.
They're my carburetor of choice for 4x4 use. If you're climbing a steep hill, they'll just creep along. Edelbrock/carter do ok too, but Rochester if far superior in that application.
@@hilltopmachineworks2131 I haven't done this, but I've heard of this. Supposedly it works pretty well because gravity is forcing the fuel towards the primaries rather than away from them.
I find it funny how the dog made its rounds around 4 X's while this video was made. This was another simple video on extra information that I just learned. Thank you and a hello from San Antonio, TEXAS.
I saw a 1965 Chevy Impala 396/325HP with a factory installed Quadrajet carb. So GM introduced them in 1965. I had a 1985 Dodge pickup with a 360 and a factory installed Quadrajet. It ran great.
I never owned a car with a Q-jet, but not because I avoided them. The only 4 barrel equipped car I ever owned was an '84 base V6 Camaro with a 2 barrel 305 yanked out of a '78 Malibu. I ran it pretty stock for a bit, them I swapped in a Holley Street Dominator with a Carter AFB 625cfm. I was going to pick a different intake and throw a Q-jet on it, but my buddy sold me the Carter AFB brand new in box, CHEAP, so I selected an inexpensive square bore intake, and I never felt like the carb was a limiting factor on the rezt of that build. (Accel ignition, headers, DynoMax Turbo II exhaust...) I hear different opinions about the Q-jet, from "They're JUNK!" and "Quadra-SUCK" to "Great, reliable carbs!"
I think they hung out to 1990 on some 307cu in. but Tony is right on with his observations. To some degree people love what they are familiar with. I like the Q-jet, I know it. No component is perfect but those are as reliable as anything made and have good throttle response. Everything is made with a purpose you just decide what fits yours. But now Uncle Tony, I want you to hot rod one and show us all how it turns out!
Congratulations on your 4 years on the air helping out with their cars. I wish you a great Labor Day from my family to yours. I have been around from day one and I will be continuing to yak, like and share your videos until you go off the air. God bless you all and I will say the same for your friend The Bennett family. Good morning to you and I hope that you have the time to comment back. I had a few of them on late 70's Pontiac Trans Am's, Chevy Nova's, and a couple of Oldsmobiles I only had a problem with one that wouldn't idle and it sat at a car lot after being wrecked for a good time and a rebuild fixed it and it was the only problem with them I ever had. Great day to you all again, thanks for sharing your milestone with me and my family/friends.
"CHOO-WAAH"...my rendition of the Q-Jet secondaries kicking in. The phenolic bowl float had a habit of gaining weight as well. Spread bores the way to go for street rodding. The 440 Chrysler NY'r Thermo was perfect for SBC 327 builds. Some versions had a cool solenoid activated idle circuit leaning feature that added to the idle loping of the cam which was always cool to kick in at a red light making it sound even badder...fun days for sure.
If you look at 1967 Q-jets and their intake manifold, you will see they have a channel in the base plate that runs under the fuel bowl that is fed exhaust gasses from the intake. This heated and vaporized the fuel in the bowl. They did away with this passage in 1968 which solved a lot of the issues. If you don't drive in the cold, block off the heat crossover in the intake manifold and you won't have heat issues with the Q-jet.
I'm in the pro Q-jet camp, I run late '70s chevy trucks, all with Q-jets. I like them for economy and low end throttle response, I almost never even open the secondaries on them. They were introduced in '65, then became widely used in '67. The bowl design, float and needle valve were refined in the late '60s to increase bowl capacity and to give the float more leverage since they had problems with the fuel pump overpowering the float and forcing the needle valve open. It was also around this time they started using extra thick base gaskets to try to reduce the heat getting to the fuel bowl for the problems you mentioned. You're absolutely right about a conspiracy to make gasoline less volatile around that time so it wouldn't evaporate so quickly, but it wasn't a conspiracy between GM and the refineries, it was done because of govt. pollution laws to reduce emissions... less fuel vapor polluting the air. It was also around this time they stopped making external bowl vents on carburetors, and shortly after they introduced charcoal canisters for fuel vapor storage (evaporative emissions systems) and stopped making vented fuel filler caps. Anyway, if you're having trouble with vapor lock on your Dodge truck, you're best bet is to just swap it to a thermoquad so you don't have to modify throttle linkage, etc... You probably already know that you can get a base gasket that helps insulate the fuel bowl (two designs, one is open under the fuel bowl, the other closes off the gap under the bowl) but they don't always work and may not work at all on a Dodge for all I know. I like to block off the exhaust crossover in the intake, that seems to help the most, but then you also have to convert to manual choke, which I prefer anyway. The older 4MV Q-jets (up to 1974 in cars and 1978 in trucks) are less prone to vapor locking than the "modified" M4MV Q-jets (1975 and up in cars and 1979 and up in trucks), but the later ones have much larger fuel bowls and more adjustments so the're better for performance.
The 1986 k20 suburban I grew up in had a quadrajet, it was replaced with holley pro-jection, and put back on because the holley ECUs wouldn't last. My dad claimed that when properly tuned there was a 1 or 2 mpg difference between the q-jet and fuel injection.
Quadra Jets are now being sold on Ebay as they are made in China and the average price is $250. If they are an exact copy they are a damn good carburetor. My advice would be to use a a phenolic resin or plastic one inch spacer to keep it cool and a high output mechanical pump to feed it. Use a 3/8 inch supply line. Anything smaller will cause problems.
Actually a damn good carb - once you figure them out. I ran 'em on all my Chevys, a few Fords, even an IH pickup I had. Guys forget, at WOT any two carbs with the same airflow and fuel mixture make the same power. I like that the Q-jets fuel curve can be tuned so close, and the only issue with making big power is the tiny fuel bowl - which there's more than one way around. Holleys are fine - they're simple and easy, if that's all you want.
I agree ! I replaced a Holley with a stock 1973 Q-Jet from a Chev. Blazer on my stock 1976 Jeep 304 . Much improved acceleration and great sand dune climbing ability !
TONY- Your good, you know what you know. You don't know what I know. Did you know the quadrajet air horns warp which drips gas at the booster and causes idle problems? This is because their made from pot metal, and I would take off the horn, beat it flat with a hammer, and even if cracked, it stopped dripping and ran much better. I did this often in twin engine race boats and cars. Other than that( cheap metal) they were efficient. THERMOQUADS (YOUR FAVES, RIGHT?) Were very expensive because they were made with AIRCRAFT grade aluminum, the phenolic resign bodies DID NOT WARP ( one time there was an engine fire due to a leak- the Thermoquad though in the fire, only needed the idle air bleeds cleaned up in the passenger side where the fire was- the phenolic body was fine to my surprise! NOTHING can be tuned to produce the best mileage AND power than the THERMOQUAD- and their VERY light too! I saw your video years back with a very tragic, highly abused vestige if a Thermoquad with impossibly rusted throttle plates and a phenolic body with a chunk out of it somehow! Can't speak to what the hell that thing went thru, but I have built MANY T-Quads without any such issues. Biggest problem was the primary jet wells epoxy letting go and leaking into the recessed area of the base/throttle plates, causing slow leakage that produced a rich idle- Marine Tex white epoxy kit fixed them permanently (JB weld would only last a few years or so). THREMOQUAD was the PINNACLE if carburetor development for COMBINED STREET/STRIP. We will see with the new Edelbrocks! (Which are based on the avs afb Carter earlier design than the T-Quads, competition and superquads. No other carb EVER had such small triple boosted primaries with giant secondary dumps on STOCK 850CFM. NOBODY. IF more people understood the T-Quad they would be fans. They were that good, but VERY expensive when new, again, the biggest quirk was the jet wells, which the Marine-Tex solved.
Hey UT, John and Ashly in Canada. Just want to thank you for sharing your carb knowledge and passion. I love carbs . Fixed my accelerator pump in Mexico (67 Rambler, 232 2bbl) with a tassle from my girls leather coat and a razor blade and screwdriver. That was in 1987 when I was 21.
Once you figured these out they are great carbs and only hated by those that dont understand them. Pull the secondary dashpot (vacuum pull off) rod and set the air door spring correctly and you have a nice no bog secondary kick in. Vacuum pull off slows down the air door when it has vacuum and is slow to react. Drill out the idle air bleeds and it takes care of the idle issues with bigger cams. The good thing is these came with all kinds of jets, springs, rods and metering holder heights and can be perfectly tailored to any engine.
JB Weld has always worked for me to eliminate the well plugs leaking. Although, using JB Weld that will hold up to modern ethanol enhanced fuels is imperative. Also, some of the later Q-Jets were sought after by street guys due to the larger fuel bowls. You’d know these in particular, as the air horn has more screws attaching it to the fuel bowl over their older derivatives. (Think just prior to the CCC carbs.) Those had double vacuum breaks, and the bigger float bowl. They were the Chevy hot rodders dream carb. I believe they were only made for a couple years before they all went CCC.
I've only ever had trouble with jet wells leaking on the very early Q-jets. I've seen lots of the later ones "fixed" with JB weld that didn't even need it and the epoxy turns brittle after several years and flakes off anyway. The only way to permanently fix leaking jet wells is to remove the lead plugs and tap the holes, then use set screws and put epoxy on them like pipe dope.
@@livewire2759 that's exactly what I do. But I use aluminum rods and thread them, cut to length and cut a groove on the end. Use extreme high temp thread locker on them.
You can run a mill slot drill down beside the float bowl at the rear. Cut both sides and it opens up another 40% volume for the float bowl. Here in Australia, we couldn't run a NASCAR mechanical pump on RHD 1971 -84 Holdens with power steering, so I ran a mechanical pump with a Holley red pump working off a kickdown switch and relay. No starvation in hot Aussie summers and it was more reliable than a Holley blue pump. Cheap throttle shaft bushes are 30 cal (30-30 or 30-06) cartridge necks cut off and locktited into the baseplate. My Hillbilly cousin taught me that. For mild street cars up to 1.3 HP per CU/IN, they have no peer. Still the closest carby to fuel injection.
@@paulgill5813 I'm positive, it blew me away when I walked up and the hood was open, there sat a quadrajet. Of course the motor was worked on, had state of the art heads, cam, etc.
Had those on my first 76 Impala 400 small block. Got 20mpg if I stayed out the throttle and made the coolest sound wide open with the air cleaner top flipped over.
Fellow lid flipper. had my all stock 72 k20 lid upside down always howled up the hill to the scrap yard with a load of junk.. miss them days of being a poor kid with a cool truck
I love the Q-jet. I always used air/fuel gages, vacuum gages, timing lights to tune them. I also found that a fuel pressure regulator helped with a lot of the fuel issues relating to heat and small bowl size.
My father could make a quadrajet carb produce he loved them too. He wasn't a professional mechanic but so many guys dropped carbs by the house for my dad to work on. Besides as you said they were the best moderate to higher performance carbs out there and they were cheap. After he passed in 06 I had boxes full of carbs and parts and I'll tell you I had guys begging for what I had.
In 67 & 68 the intake manifolds had the exhaust heat crossover also going through under the base of the Qjet and used a thin gasket with the stainless steel thin heat shield. The old 2GC actually had the exhaust running through the base of the carb! In about '69 they deleted that system. Chevy did make a Qjet aluminum heat shield too
I think that is partly the reason why GM went to the 1 piece rear main seal after 1986 , oil leaks and fuel vapors were then included as part of the total vehicle emissions
when i started running a Qjet on my 1966 GTO i had to rig a fuel return line to the tank to solve the vapor lock . this was about 2004 before that i had ran a holley anda 2 bbl without vapor lock problem.
@@repete2362 i don't know about the earlier ones but I'm sure 68 and up came with higher volume fuel pumps. It had a 3rd line on it for return. You could always tell if someone swapped out there 2bbl for a Qjet, the fuel pump only had 2 lines.
Yeah I hear ya,. Back in the day those quads made my little chev 265 and 283 go like stink compared to the stock carb. Never had a problem with the heat . That sound was great.😂😂👍
I think you're right, but" Quadrajet is either great! or it sssuuucks and needs to be dipped and rebuilt. As for performance I have seen some that were amazing and beat every thing out on the road. I had one on a firebird formula that should have never been able to do what it did. Then again I had one on a chevy truck that many times I wanted to take a hammer to it. But all around a Quad is a awesome carb and I will run one and be happy with it.
@@christianperspective9527 I remember early on that a lot of vehicles did not have internal pressure regulation in their fuel pumps, and when I would install a newer pump on a car, I had to rig up a return system to the fuel tanks.
I had mine on an FE Ford, and I made an aluminum heat shield that want out and up to keep the heat away and always block the heat passages in the exhaust ports with a thick piece of stainless steel in each sides port shaped in the bowl and Devcon to seal the bowl and a thin piece of stainless in the gasket passages installing it. On an FE half of the head is the intake. I liked the Holley SD and used a homemade plywood adapter where I started a spreadbore shape and sealed the adapter with a gasket and it was matched to each with the heat shied and I wore that carb out, daily driver street racing, it was perfect!
I love Quadrajets. I pick them up whenever I find them, dedicated manifolds too. I used to run a '71 big block Camaro in D Stock Auto and learned early on how to make them run. It's not difficult but they can be made to be fully adjustable and few people know even the air door spring (opening) rate is adjustable. Once set up they just put down the power to the road, I especially like the 800 cfm models. The well plugs are easily fixed, there are kits to rebush the throttle shafts and you can modify the carb top to allow access to the primary metering rods and they can be adjusted with a large tire valve tool. I've had my best luck with an electric fuel pump and regulator set to 8psi. Doesn't matter if it's a 455 Pontiac, 500 Caddy or a stroked 510 ci big block Chevy, even a 283 they just perform and I have done a head to head with a Holley 750 and especially on the street you can feel the difference and smoothness of the Q-Jet. And yes, I have a couple Thermoquads sitting on the shelf, one off a '73 Charger with a 400 and the other off a '72 Polara cop car with a 440 just in case I run into a Mopar project.
Getting that air door tension right was one of the reasons so many hated them, or used the "quadrabog" moniker. Few amateur tuners really figured out the secondary metering rods and airflow through the upper doors weren't directly coupled to the rest of the throttle linkage, but depended on that spring loaded shaft opening at just the right rate.
I always liked the 850 Buick Stg1 carb and they actually made a 1708 replacement for the Buick Stg1 to run in NHRA class for the 430 and 455 cars. The Pontiac 400/455 Qjet was 800 cfm and had slotted secondary air valves with pullover secondary enrichment that as soon as the throttle blades moved it pulled fuel until the air valves began to open and lift the hanger and rods.
I have found that a trans cooler between the pump and carb solves the heat soak issue. It can be 95+degrees and the carb is cold to the touch. Also insulating the fuel line from the cooler to the carb is a good idea.
@@geosradiomusicalstuff3124 I will add that I have only ever used a stock mechanical pump while doing this. I would guess that a trans cooler can handle more pressure but I'm not sure how much.
Three guys came to my garage one day about 10 or more years ago from the then known as Nashville Auto Diesel College. One of the guys was a regular visitor and familiar with most of what I was doing. Upon coming to the bench one of them looked at the to be assembled piece and asked, "Whats that?" I looked puzzeled and said to the group, "Your kidding me, right? Don't they teach you about that at NADC? (They were in school uniform as they were on lunch break.) It's a Quadra Jet carbureator.", I explained. There was a brief pause followed by the question, "What's a carburetor?" True story. This was a great video and thread like none I've ever seen!
Thanks Tony for throwing me back in time. I will never forget the 70 Chevelle SS I had with the LS6 and cowl induction. I think the rochester was the 800cfm version. When the 4 barrels opened up the sound coming through the cowl induction was unreal. Thought it was going to suck the windshield out of the car. I had a buddy that did some modification to his on a 69 vette BB that supposedly got it to flow 1000cfm.
@@racer44x Actually you are correct the engine had a holley on it originally. The manifold was a square bore also. I did not have an adapter but did have a spacer. So dremeled out the secondary side of the spacer on the quadrajet side to fit. So many years ago. The town was 3300ft above sea level and at the time just could not get the holley to run right. Also would eat so much fuel barely had enough gas to get to the next town.
The best video at the table is the one where Kathy is trying to talk Tony into doing videos, bag of chips flying, Tony runs and tries to hide behind the garage only to be convinced by Kathy telling him they could make money, Tony says I like money... classic!
@@thefinalroman Strange, I have owned many cars and trucks with 350's and 305's with the quadrajet and not one of them got bad mileage. The worst quadrajets were the ones with electronics on them, they were TRASH! Unless you got a 454 big block hauling a load you aint seeing 5mpg with a clean quadrajet. I will always be a Mopar guy though,haven't bought a chevy product in around 25 years.🤣
@@u.p.tinkering Every quadrabog I ever had was from the 80's so it definitely had the emission crap on it. Air pump and various solenoids + huge vac diagram. For some reason every other 80's car with all that emission crap ran fine. Toyota,Honda, even K cars (Holley carbs 2bbl)
@@thefinalroman Yeah those ones really did suck. My favorite car was a 83 Turismo 2.2 with the 5 speed. It had the Holley 2bbl ,I really loved that car and ran it for years into the ground. To find one of those Turismo's now is near impossible. It was the black and gold accent one.
Holleys need constant attention. Edelbrocks are a bit funny. The quadrajet is a set it up and no hassles if you set them up right. They are not repeat NOT performance carbs. They are street friendly and if you get your timing set right, and secondaries where they can drop the venturi flaps down they will light up like a rocket. They work. They are reliable. I love them. Easy to rebuild. Easy to set up. Like you said though, the bowl will dump out. Heat soak can be solved by restricting the exhaust crossover.
I have a 1966 Olds which came with a Quadrajet so 1967 was definitely not the first year for the QJ. In fact, the 67 Olds came with a completely redesigned QJ compared to mine (vacuum damped secondary's rather than fuel dampened) so by 67 they were already onto a second iteration of it. Great video though, love the review.
In '66 they were only used on the 396 big blocks, but in '67 they started using them in almost everything, except trucks which didn't get them until '69 or '70.
I learned the QJET on my Toronado. After replacing rocker arms, pushrods, and intake. First fire it had a huge backfire out the QJet and split it at the secondaries opening. I loved cruising in it. I liked the kick of the secondaries opening. 800cfm QJet on the 455 Olds was pretty fun. It was the first not lawnmower or tractor carburetor I rebuilt. Will still hold a place in my heart even though I'm 21 and only had the QJet for a year and a half.
The super early ones, 1965- around 67-68 used a heat passage directly under the carb base and required use of a thin, metal sided gasket and those would really heat up, sometime in the late 60s they quit using that whole system and started using the thick 1/4in gasket with no heat passage which greatly reduced carb temp.
The moment I saw those wee primaries and honkin great secondaries I knew I never rebuilt one or owned one. But I rebuilt many earlier 4bbl GM carburettors and noticed that people would quite commonly lock the secondaries out to improve gas mileage. So based on that experience I think GM did a great thing to do an asymmetrical design.
The Qjet. Hated by millions who never had a Qjet set up correctly. Hearing the four barrel working through functional arm air is muscle car bliss.
I always loved the deep-throated sound that came when you jammed that gas and the car would leap forward!
@@dangeary2134 BWHHAAAAAAAAAAAAAAAAA
This.
The only reason it makes that noise is because it has big secondaries and it is all vacuum when they open up I absolutely hate quadrajunks. They're almost as bad as the Carter thermoquad.
@@billthompson5644 so you agree it makes that noise. Thank you for verifying that your internet connection works Bill.
As VGG once said. The people who don't like Quadrojets don't know how to tune them.
Trash carb. They never ran right only fools take em out the trash and praise them.
Very reliable carburetor. No 4 BBL sounds better kicking the secondaries in !
With the air filter cap flipped.
The Thermoquad makes a similar sound. I really like the T-Quad, but the Q-Jet is a good carb too.
it's the sound of any spreadbore. sounds great.
Indeed: when those storm drain secondaries opened, you understood "Big & Littles" wasn't just referring to Pro-Street tire stagger.
Only sounds fast.
The Rochester QuadraJet is the greatest carb ever made. The fact that I'm a lifelong resident of Rochester and live maybe 10 miles from where they were made has nothing...NOTHING...to do with it 🤣
I was born in the same small town as Larry Bird.you can't tell me he was'nt the greatest man to touch the leather of a basketball so I completely understand where you're coming from! 😆
@@johnsheetz6639 Ah. "The hick from French Lick." Helluva player.
Living in Rochester and hot rodding peoples cars you hsd to know the cure for the Quadra jet bog. Take the top off and remove the internal parts look at where you can remove part of the wsll inside of the carb to hold more gas and eliminate the bog . FORD used those carbs on the 429 CJ and Boss 351 without any problems and those original carbs are worth real big bucks .
@@bcubed72 that's what I'm saying! Lol! Thank you for the reply! how many cubes? Your name peaked my interest!
Is the Quadrajet a drink they serve at the Wintonaire yet? 😉
The best thing about a Q-jet was that they always worked. As long as you kept them clean, they were trouble free.
And no denying that sound when you opened up thoes secondaries!!
@@robinluck2922 for sure! 👌
Carry a clothes pin.
They were easy to clean the jets, too.
I simply pinched the fuel line to drain the float bowl while it was running.
Shut it down, and then take the spray can of carb cleaner and fill the float bowl with it. Run it until the bowl was empty again.
Let the fuel line go, and they would run like a top!
Does anyone remember how we used to pour a bit of water into the primaries to loosen the rings, then a bit of ATF to clean the valves?
my buddy had 85 monte carlo SS and yes I know it did not have lot horsepower compare to today cars but when the four barrel open is when the magic happened. Brings back great memories of late 80's . Thanks
I had 84 and 88 SS's bucket seats but my buddy had an 88 SS with a bench seat and colomn shift and man I loved that bench seat. I've looked for another SS with a bench but they must be rare. Love Qjets never understood why people hated them. That baawaaa sound was awesome to hear. I just traded for a couple and one bop.
Opened those things up, loved the " moan " when that 4 barrel come in ! 👍
My 86 SS was gutless until I found the secondary spring was too tight. A little bit of screw tweaking to the limit - no bog just sweet waaaaahhhh!!!
If it works. Which it won't...
I had one on a 84 Z28 perfectly matched to the car. Ran like a top. Hit the gas thing would jump. Secondaries would open........
Worked at a cad/ olds dealership had an old mechanic that replaced several a week! I snagged everyone I could pulled apart, had all sizes of jets, metering rods primary and sec. Different power valve springs ! Loved the carb in a 350 I built in a 3/4 ton pickup never a bog or stumble start to a pegged speedo. Lot of part switching at first but boy did it work great. Thanks Tony. God Bless.
My 86 GMC came with a 4.3 V6 , 3 speed on the column and non electronic Qjet. Switched the engine/trans to a 350/350 , then a Vortec 305/350th. All I've done to the Qjet is to rebuild and replace the throttle shaft bushings. I've always said- Qjet for every day driving/fuel mileage and a Holley for performance.
I still go to the wrecking yards and pull metering rods and hangers.
Honestly as a kid I was the little jerk at the junk yards taking all the q-jet parts I could fit in my pocket.
@@brianjones5117 sitting here laughing because we filled our pockets with everything.
One time we wrapped a shift cable around inside our clothes.
@@eddieb4227 i know huh I mean we didn’t have a ton of cash as teenagers and the parts were everywhere. Besides the junkyard more than made up the difference in overcharging on other parts
Quadrajet, the finest carburetor ever made. The haters don't understand how to tune them, and that will make you hate it.
I think most of people hating ran bad gas through them. Or had a square borentake they bought. It doesn't require much to go fast back in the day open Element air cleaner headers and a napa cam although the days I seen that stuff was the '80s don't sleep on the 305 you can catch some mid 14s with a good gear. On the peg leg too!
Well it's just like the Carter Thermo bog if you don't know how to set it right or watch out for that plastic float breaking it's going to give you nothing but trouble
@@truckerkevthepaidtourist ThermoQuad float issues? I tried & tried but the dipstick in my freshly rebuilt 340 always smelled like gas, and the highway mileage with it was appalling (3.55 posi rear end)
@@peters8758 yeah you have to find someone that really really knows them and has run them for years to rebuild them properly and set
Trash carb that leaves u stranded or on fire.
I rebuilt one. First time for a 1968 Toronado. Followed the instruction sheet and that car ran like a champ. Even the choke was perfect. Great carb.
To think the quadrajet has been “out” of production longer than its entire run of 21 years lol… man time flys!
Still the best street carb.. especially when it comes to weather up in Canada where I’m from.. still use a edelbrock rpm 1910 quadrajet on my big block 67 Chevelle, got sick of sticking floats, crappy gas mileage in the Holley’s not to mention the constant tuning whenever the temp started changing!
Actually he slightly erred. The Q-jet was first introduced in 1965 for the big block Chevys, and went out of production with the end of the 1990 model year Olds 307 engines.
Noting how most drive, a typical square bore 4 barrel sees something odd regarding street use: the 40-60% throttle range is darn near a dead band: people are either cruising or passing. The q-jet pretty near eliminates that regarding primaries.
My buddy used to rebuild these for fun. He would buy them from salvage yards and rebuild them, then put them on his shelf. His dad taught him the tricks to them.
He put them on all of his vehicles.
My favorite ones were on his 455 Buick, and 455 olds.
The sound they made was awesome. Sounded like the hood was going to be sucked into the motor.
The memories of that sound as he rolled past 5.0 mustangs with his 850 cfm sounding off will always be with me.
I always considered them to be the 1911 of the carburators.
To many parts for the average Joe to break down and rebuild, but incredible anyway..
I have a 66 toro with a 69 455 that has been tweeked here and there. The rice burners get spanked bad!
Wish I had kept the 66 trans since it had 3.21 gears Compared to the 3.01's of the 69.
Tony: On February 15, 1967 my father took delivery of new Pontiac Catalina. Stalling issues were addressed by Allison Pontiac, RIP, with the warning not to use "Shell" gasoline. The problem, as you indicated, faded away. Thanks, for the trip down memory lane.
As a life long fan of the Q jet I must confess my sins here. I have plugged those two holes that Tony mentioned with Bazooka joe bubble gum. I was just trying to get back on the road and drove on that carb for 5 or 6 months before selling the car. 2 owners later it got a Holley because that kid thought it was an upgrade. I should have bought that Q jet back.
Having fixed a shattered transmission shift linkage in a GLH Turbo using nothing more than a long shoelace - and then not installing the new shift rods for 2 years because I'm a lazy bum - I salute your field expedient repair work.
Sometimes you just gotta go with what you know.
Yeah, everybody replacing that unknown size Q-Jet with a big 550 CFM Carter AFB or Holley 4 BBL...
Qjets are the best and whoever disagrees smells like Brussel sprouts.
I started working on cars at a GM dealership right out of high school in 1995. We used to rebuild these all the time. They were still very common on the road in the mid 90’s. I would say at least one a week average. The well plugs were VERY common issue we seen.
I have one in my 87 El Camino, a California-compliant one. It’s currently hemorrhaging gas, do you know if they are an expensive fix, like more expensive than a regular one. I think I remember being told it was computer controlled.
@@BigCaucasoid I honestly don’t know how much they cost to rebuild nowadays. Yes yours I’m sure has a TPS sensor and a metering rod solenoid. It has been soooo long since I’ve even seen one of these carbs.
Most regular car guys that didn't have a muscle car had these quadrajets. Other than that choked out two barrels from the '70s man they weren't super impressive but for the day if you snatch it down first and it sings it's song much more impressive than the 301 Pontiac 2 barrel your friend had
hell glass packs off the y-pipe for effect cause you bought the car for $500 and you can bragged your friend it goes 45 in 1st cause it had 256 malaise
gears!
Thanks N8
You can get a kit for $40 and easily do it yourself with a few UA-cam videos.
The adjustability and the ease of maintenance on the QJ are its strong points.... along with great part throttle fuel atomization. As stated, the fuel bowl area leaves a lot to be desired, but on a small-cubic inch V8, these things were amazing. Lots of torque, great throttle response and, when the urge to pass somebody hit your right foot, they got up and flew. Great review!
great for a DD, riser setup helps AND isolates from intake manifold heat. its always been an easy inexpensive kit. more air flow under the air cleaner with the carburetor and fuel line an inch higher, common sense simple.
I am an off road guy. What I can tell you is the Q jet is hands down the best off road carb out there. The reason it works so well is the exact reason UTG cites as a disadvantage. That is, it's small float bowl. When you are off throttle, even a small amount of gas spilling into the manifold would kill the engine. Off camber would starve the engine. Imagine moving down a steep, ruff incline at idle. With a Holly and it's comparatively gianormus float bowls gas can just spill through the main jets, put the fire out in a heartbeat. On throttle on woops you could hear the engine sputter and the tell-tale puff of black smoke. Holly recognized the problem and made accessories, which I dutifully installed, but never really solved the problem. Power brakes and steering are compromised at the worst possible moment. I rolled my jeep onto its roof and my Q-Jet was STILL RUNNING. I actually had to reach up and turn off the ignition. Loved the Q-Jet, next best thing to Fuel Injection, which is what I have now.
If your off roading to those extremes grow up and put EFI on it. It is about as cheap as the carb and proper tuning.
I'm kind of thinking I went the wrong way on my car with a junk carb from hell.
@@heavymetalmadness666 Apparently you didn't read my post. My 4X4s are all equipped with FI now. I've been off roading since the seventies, before fuel injection was even a thing. Here's a little advice that you didn't ask for, you're better off to stay silent and be thought a fool rather than open your mouth and remove all doubt. Oh, and another thing, I learned back in the sixties. Back then, they actually taught kids stuff in school. For example, I learned the difference between you're and your, you should look into it.
Amazing...!!
@@heavymetalmadness666 My reply was probably to long for a typical OCD such as yourself. I did now go sit in the corner with your dunce cap.
I had one off a Cadillac 500 on my 11 to 1 purple cam 440. Ran awesome excellent throttle response and gobs of power. No adjustments just bolted it on.
The QuadraJet is without a doubt an excellent carb. They do make strip kits for them, and the fuel delivery issue as a result of the incredibly small bowl can be helped by what you mentioned; different size/shape floats, bowl contouring, as well as larger orifice seats, and windowed seats. I ran deep 11s with a 69 Nova street car, very mild pump gas 454 and a 4-speed, with a HV pump, and a larger/windowed needle/seat. Never nosed over once, and was as responsive as EFI
I also have over 2 dozen Thermoquads in my “collection”, most of them being the early 6xxx series, and two aftermarket SuperQuads. All are excellent carbs. 👍
GM ran em for decades for a reason. Most reliable carb ever made.
I had boxes of these years ago, I learned a lot of the tricks to them and with several tweaks and small modifications I had very good results from them. The most misunderstood thing was one you learned how to work with them, they remained set, whereas Holleys you had to fart with anytime the conditions changed. They could actually be very hot carbs once you figured them out.
Back in my days of wheelin trucks, the QJ was the ONLY carb that wouldn't flood out in nasty off camber situations. The right would have to be almost on it's side to flood the QJ.
My 85 Elcamino at one point had the HO intake and Quadrajet pack. It wasn’t anything too hot, but was definitely more fun then most daily’s.
I found a cheap edelbrock 650, rejected it to match and it was great. Much more lower end and a nice response all the through. It was a little more thirsty then before but that was obvious and didn’t matter much.
Then I made 3x my money back selling that one, bought a new proper sized Holly. It took a lot longer to find the sweet spot between everything, felt similar to the edelbrock de tuned, and was just a little better on fuel. But once I got familiar with tuning it, it became second nature. Although anytime I would be driving through states, to the ocean, or over about 1,500 feet from last mixture adjustment I would always end up tweaking it at the fuel station or pretty view.
It the time I didn’t mind it al all. Getting under Emily’s bonnet was never a bad thing.
What are these "tweaks and small modifications" ?
@fivestar8337 Make sure the plugs in the bottom are properly sealed, float settings, and a big one is increasing the spring pressure on the rear butterflies to eliminate the bog. (I don't remember specifics. It's been 40 years ago).
Quadrajet is poor man's fuel injection. My K5s love them! I was stuck in a hole at 45°, and the quadrajet didn't miss a lick for an hour until I got the winch to reach something that would hold.
One of the things that separates the Q-jet from other carbs is the off-idle circuit. All other carbs only have idle, main, and four barrel. The Q-jet offers a fourth circuit...idle, off idle, main, and four barrel. Another known problem that old Q-jets have is worn throttle shaft. A worn throttle shaft causes vacuum leaks, and the throttle primaries to hang up.
Worn throttle shafts and leaking well plugs!
All true. However, very fixable. I have done many of them with great results. I am in the the camp that loves them.
"All other carbs only have idle, main, and four barrel." Ignoring the "four barrel" part, what you're claiming is that all other carbs only have idle and main.
That's not correct. Others have an "off idle" circuit as well, the Dellorto DLRA being one of them. In fact, the DLRA off-idle circuit has its own jet, so the carb can be tuned for idle with the mixture screw, off-idle with the idle jet, and main with the main jet and an "air correction" jet (an air bleed).
Thermoquads have an off-idle circuit as well. A couple years ago my 72 Charger developed an off idle stumble, turned out the jets used for the transition were not getting fuel.
@@ShawnD1027 As soon as you saw my post you probably did two hours of research to find some obscure brand of carburetor that had an off-idle circuit just so you could say I was wrong.
Rebuilt hundreds of " Quadrajunks " during my 49 year wrench career . About their only real problem was often overlooked - the wallowed out primary shaft hole in the throttle plate creating huge vacuum loss . Aftermarket bushings were a simple fix .
You nailed it, been down that road on all my Q Gets.
Yeah it makes the idle go up and down
Also the secondary air valves sticking because the top plate has been bent due to overtightening. Creating that Quadrajet 'bog' when the secondaries open.
And the soldered plugs under the bowl that were prone to leaking causing the common run-on or 'dieseling' issue.
As usual easy fix
My 1973 Pontiac 400 had a phenolic spacer under the carby and never had vapor lock.
The Quadrajet is the center of the famous story of the Pontiac that hated vanilla ice cream. A classic.
Tony I'm a huge Q jet fan. I love the way they drive on the street, the sound they make when they're floored, and the snap off the line those tiny pimarys create. Have you ever read Cliff Ruggles book it's actually really good about getting quadrajets set up for high performance. One thing that really worked for me was adding an electric fuel pump because the mechanical pump couldn't keep the bowl full at wide open throttle. Also Victor Reinz makes a thick gasket that actually helps keep a little bit of heat out of the carburetor. And they're actually application specific because I think there's two different gaskets for Quadra Jets and it has something to do with the little notch on the primaries. Also they redesigned the Quadrajet in like 71 or 72 when they went to that shorter Quadrajet. I wonder if that was something to try to fix all the vapor lock issues you were talking about. I don't know why but I could never get the Holley Spread Bores to feel as good as the real Q Jet they were always very soft off the line.
I had an issue with a big cam 455 pontiac sucking the bowl dry at highway speeds it would start stuttering and starving for gas, let off a bit and it was fine lol......I ran bigger diameter lines, a larger fuel filter instead of the small one in the carb and a high volume mechanical pump and it was ok after that. Cliff's book is terriffic.
I bought a 68 GTO in 1976 & as a young man thought I was doing a good thing by replacing my stock Q jet with the New Big & Bad Holly spread bore....
The Holly started to act up with in a year I Rebuilt it 2x with no results so I put the Q Jet back on & it has been working fine to this day...!!!
I still have my Goat...😊😊
I've rebuilt a Qjet with the wrong rebuild kit because the parts store didn't have the correct one and it worked. I've broke down and sprayed one down in carb cleaner and starting fluid in a 1966 Olds 98 and limped it 30 miles home. Nothing wrong with it on a driver.
Never had a problem with the Quadrajet aka the “QuadraJunk”.Great cruising carb when tuned right
All carbs are good when tuned right.
@@cammontreuil7509 no. The electronic feedback Rochester stuff was trash. Tbh, all Rochester stuff is trash. But some of it can be made to work OK.
Junk carb period. Had 10+ cars with that POS carb and they got 5mpg when they weren't broken down or on fire...
I used to love it after a rebuild when the owner drove it for the first time…I’d set it up so the secondaries and the downshift hit at the same time. A strong stock engine could bark the tires. Saw a LOT of really wide eyes!
Love the dog doing laps around the house!
Lol. It's all I see now
I'm just happy you didn't shatter the glass on your patio table with the carbs
Got my father in laws 76 Ramcharger, equipped with a quadrajet, running today after sitting 10 years. Runs like the day it was parked.
It was a dodge man many years ago who taught me how to rebuild and tune the quad.
Once again a dodge man helping the Chevy people.
The
Dodge Boys where the best..!!
There were a few quadrajets in 1965, they were on most GM four barrel engines in 1966.The last was a 1990 Olds 307. Carter also made some quadrajets for GM. They look identical to the Rochester.
My 69 Camaro had a Carter Quadrajet on it from the factory.
My 1970 Pontiac Grand Prix had a Carter Quadrajet.
The first engine that came with one was the 396 when it debuted in '65.
Indeed carter made quadrajet carbs as well. My 1973 impala had a stock 350 with factory dual exhaust and a CARTER quadrajet. Great running car. Miss that car.
Q-Jet first used on the new for 1965 L35 396/325hp V8. 1966 saw an expansion across the GM lines, but not full use.
in late 70s had a Qjet on my 455 olds motor, never bogged off the line ever, when it hit the secondaries would literally smack the top flaps wide open instantly, GREAT CARB
Had one on my first car ever...man, what a sound it made after you flipped the air cleaner lid. Made a teenager grin ear to ear!
The Thermoquad on a 340 is great! And tuning the T-quad is as easy as an AFB. I love the metering rods especially the 3 step.
My father built his shop, business, and reputation on that Q-Jet right there. He did them all, but that was his bread and butter. But the vast majority of all of them where for people just wanting to go down the road. Drivers not Racers.
As for the Secondary Metering Well Plugs... that was dad's secret weapon for success in all that. We bought the factory Re-Build Kit for them, with the O-Rings (QJT-1 & QJT-2 part numbers if I remember right). Drill them out and pop in those plugs and they run forever. We used to buy them by the case, and still have about a half a case of them left over...... I think it was a $2 part and only took a couple minutes to install. One of these days (now that dad has fully retired) I'll get video of him installing them 1 last time.
Good Video as always UTG!
Never used a quadrajet, but I love the T-quad.
I have a 1972 C10 Pickup which had its original 350 engine with the QJet 4bbl carb. Over the last few years a knowledgeable friend who has built many Chevy engines built a 30 over 400 small block for me which will has about 325/350 HP and 400/425 ft lbs of torque. When starting the build I asked if we should get a Edelbrock carb, as the QJet has 91000 miles, for the new engine and he said no reason as the QJet is all we need and he was going to rebuild it which he did. He said people do not understand them and they are a great carb. My engine and the rebuilt QJet are working well together.
The best street driving carbs i've ever owned were, and still are, quadrajets. One of mine has developed the well plug issue. a few years ago it was very slow and would only leak out over the course of a few days. Now it leaks down in less than a few hours. Need to pull it off and fix it. I should probably send it off and have it rebuild because it's leaking air through the throttle shaft. Guess even the great quadrajet isn't susceptible to age with this example being 43 years old without ever being rebuilt. I think a large contribution to their lack of prevalence in performance applications, in addition to bowl size, is the lack of quick tunability. Where on a holly you can change jets, power valves, float heights, etc. quickly and easily making tuning far easier for the aplication.
You can reduce/eliminate throttle shaft wear by moving throttle return spring anchor point to the front of the intake manifold instead of under the throttle cable/linkage. When it is under the linkage, BOTH components are pulling in the same direction, thereby loading the back half of the throttle shaft bore.
@@wesalker3479 I'll look into that if/when I either have this one rebuilt or replaced. It's not very high up on the priorities list at the moment, unfortunately.
I agree, it was also one of the last carburetors that was able to meet emissions before EFI took over. The triple booster primary gave a nice crisp response on the primaries without trying to get ‘just right’ pump shot. Great throttle feel. I design production EFI systems now, they’re far more accurate than any carb ever was (I get A/F ratio errors smaller than 0.01% across the whole operating range, including transients), but the Q-jet really was the closest you could get mechanically.
You are absolutely correct Tony: Q-Jet fuel bowl is small. How do i compensate for that? Run Z-28 / Corvette / High Capacity fuel pump, remove internal fuel filter and run in-line filter. Change the tucked fuel line from pump to carb, (has too many bends) and run the line in a straighter fashion, away from the engine and insulate it. You are again correct when you say you can get away with it if your fuel delivery is top shape. Thank you, Keep up the good work. Pierre Lafontaine
The tiny, centrally located bowl is actually a pro when it comes to off-roading, and off-roaders still love it when they don’t have EFI. The Q-jet can operate at angles that would make most other carbs lean out on one side and drown on the other.
I’m a bit ashamed that I’ve never a run a Q-jet on one of my own cars . I’ve got probably a dozen Thermoquads, though, and I really, really love those. We all know the weak spots of that one, but when it’s not abused with over-torqued bolts and incorrect jet well O-rings, it works wonders.
True.
Remember the singer Lou Gramm of Foreigner raced the streets of Rochester and sang about Lake Avenue street racing . Could he have been a Quadra Jet user ? .I know his brother Dickie had a quick GS Buick with one .
My camaro had an electronic Q-Jet from the factory. What an absolute pile. I swapped it with an earlier model. Picked up a book with tips and tricks for Q-jets, and proceeded to create the best running street carb I’ve ever owned. Since moved to Holley’s for performance, but still love a well tuned Q-Jet
Simplicity is an asset to Holley
My 1987 Cadillac brougham 4 barrel quad Rochester cab is racing with my foot off the peddle it is still racing down the street even in park it is still racing
As an old guy coming back to a classic car, this was a terrific breakdown of the Quad-J. It was clear, simple and to-the-point, I have subscribed to your channel and look forward to digging into all of your tutorials, thanks Brother!! (currently resto-modding a '68 Impala Custom Coupe, wish me luck :D))
Lovingly known as the quadrabog . If people would read a little on how to adjust them they actually flow 750cfm and I have absolutely never seen one that wouldn't run even sitting for 20 years or more . Fuel economy and hp all in 1 carb
Being a young 20 year old car freak myself, it's so nice to see some love for this carburetor, the quadrajet and thermoquad will always be my 2 favorite carbs just because of that sound. The sheer tunability of the Q-Jet puts any fancy holley to shame, I've been wanting to get myself a small car to swap a 350 into with this carb
Best street carb ever.. has a g body cutty 350 Chevy with a quad...I was once wanted by the police and was identified by the sound of the 4 barrels cracking open, you could hear the gas flow dumping.. duuuuwwhoooppppp duuuuuwhoooppppp
Love the Q-Jet! Lost count of how many of them I have fixed/overhauled/tuned. Doug Roe's book was the bible for these carbs.
It is and he unravels the mystery.
I had a 73 stepside and after a few rebuilds over 300000 miles I never had vapor lock issues. I installed an Edelbrock Performer manifold so maybe aluminum behaves differently.
The correct rods on the secondaries and setting the air door spring made a big difference. I was just under 300 HP, so definitely not "high performance", but it served me very well. The ultimate "set it and forget it" carb. They don't need constant tweaking to keep their tune.
@@kennywhiddon1497 Yes the Olds 442 in 66 and 67 cleaned up in C/Stock. It wasn’t until the Ford FE 428CJ that anything else would beat it. 1 race Shelby Mustang fastback in 67 ran the KR8 that was a 428 CJ that gave Olds any grief. In 68 Olds ruined the 400 by putting the 4.25 stroke in and reduced the bore to get 400. The best in 65-67 were the Olds OA1 400, a 7000 rpm screamer, the Pontiac 400 Ram Air 3 and 4 , the 375 hp 396 Chevelle and the Buick Stg1. Until Ford got their 428CJ Mustang fastback, they Ruled. The KR8 428 wasn’t allowed to run but one race. I still have my 394 ci FE with a Holley now, but when I had the Qjet on it after the modifications and an electric pump with AN-08 line and a deadhead regulator at 7 lbs I would wind it to 7000 +, and even now with the 3310 750 a friend of mine put a jet block on in place of the plate, it will do 7000+ but no quick getting there than the 850 Buick Stg1 carb..
My personal experience with carburetors has been mostly with the Quadrajet. Once I leaned how all the systems worked I found it to be the most tunable carburetor and I was always happy with the results. Easy starting, Smooth running engine throughout the RPM range and really good fuel economy. Yes it has it's issues but they all do. Electronic fuel injection has really put most carburetors out to pasture.
They're my carburetor of choice for 4x4 use. If you're climbing a steep hill, they'll just creep along. Edelbrock/carter do ok too, but Rochester if far superior in that application.
I had a buddy that mounted his Q-Jet backwards in his Jeep CJ. Never had a hic up on a steep hill climb.
@@hilltopmachineworks2131 I haven't done this, but I've heard of this. Supposedly it works pretty well because gravity is forcing the fuel towards the primaries rather than away from them.
I'm not a carburetor guy but I love the sound of a flipped lid quadrajet when the secondaries open up.
I find it funny how the dog made its rounds around 4 X's while this video was made. This was another simple video on extra information that I just learned. Thank you and a hello from San Antonio, TEXAS.
I saw a 1965 Chevy Impala 396/325HP with a factory installed Quadrajet carb. So GM introduced them in 1965. I had a 1985 Dodge pickup with a 360 and a factory installed Quadrajet. It ran great.
Qjet years were '65-'90 .. 1965 Chevelle 396 got them ... Ram Air 4 Pontiac , Buick GSX 455 and quite a few others were very high performance cars
I never owned a car with a Q-jet, but not because I avoided them. The only 4 barrel equipped car I ever owned was an '84 base V6 Camaro with a 2 barrel 305 yanked out of a '78 Malibu. I ran it pretty stock for a bit, them I swapped in a Holley Street Dominator with a Carter AFB 625cfm. I was going to pick a different intake and throw a Q-jet on it, but my buddy sold me the Carter AFB brand new in box, CHEAP, so I selected an inexpensive square bore intake, and I never felt like the carb was a limiting factor on the rezt of that build. (Accel ignition, headers, DynoMax Turbo II exhaust...) I hear different opinions about the Q-jet, from "They're JUNK!" and "Quadra-SUCK" to "Great, reliable carbs!"
Can't go wrong with an AFB on a square bore setup. There are damn good carbs.
I think they hung out to 1990 on some 307cu in. but Tony is right on with his observations. To some degree people love what they are familiar with. I like the Q-jet, I know it. No component is perfect but those are as reliable as anything made and have good throttle response. Everything is made with a purpose you just decide what fits yours. But now Uncle Tony, I want you to hot rod one and show us all how it turns out!
As an english man who grew up in an era of fuel injection. I bloody love my quadrajet on my 350 69 c10!
She rips and sounds awsome!
Congratulations on your 4 years on the air helping out with their cars. I wish you a great Labor Day from my family to yours. I have been around from day one and I will be continuing to yak, like and share your videos until you go off the air. God bless you all and I will say the same for your friend The Bennett family. Good morning to you and I hope that you have the time to comment back. I had a few of them on late 70's Pontiac Trans Am's, Chevy Nova's, and a couple of Oldsmobiles I only had a problem with one that wouldn't idle and it sat at a car lot after being wrecked for a good time and a rebuild fixed it and it was the only problem with them I ever had. Great day to you all again, thanks for sharing your milestone with me and my family/friends.
"CHOO-WAAH"...my rendition of the Q-Jet secondaries kicking in. The phenolic bowl float had a habit of gaining weight as well. Spread bores the way to go for street rodding.
The 440 Chrysler NY'r Thermo was perfect for SBC 327 builds. Some versions had a cool solenoid activated idle circuit leaning feature that added to the idle loping of the cam which was always cool to kick in at a red light making it sound even badder...fun days for sure.
It's spelled CHOO-WAAAAAAH
You turned me back on to carbs and that’s all that matters 👍🏻
The sound of a 396 when the Quadrajet kicks wide open is unforgettable.
If you look at 1967 Q-jets and their intake manifold, you will see they have a channel in the base plate that runs under the fuel bowl that is fed exhaust gasses from the intake. This heated and vaporized the fuel in the bowl. They did away with this passage in 1968 which solved a lot of the issues. If you don't drive in the cold, block off the heat crossover in the intake manifold and you won't have heat issues with the Q-jet.
I'm in the pro Q-jet camp, I run late '70s chevy trucks, all with Q-jets. I like them for economy and low end throttle response, I almost never even open the secondaries on them. They were introduced in '65, then became widely used in '67. The bowl design, float and needle valve were refined in the late '60s to increase bowl capacity and to give the float more leverage since they had problems with the fuel pump overpowering the float and forcing the needle valve open. It was also around this time they started using extra thick base gaskets to try to reduce the heat getting to the fuel bowl for the problems you mentioned. You're absolutely right about a conspiracy to make gasoline less volatile around that time so it wouldn't evaporate so quickly, but it wasn't a conspiracy between GM and the refineries, it was done because of govt. pollution laws to reduce emissions... less fuel vapor polluting the air. It was also around this time they stopped making external bowl vents on carburetors, and shortly after they introduced charcoal canisters for fuel vapor storage (evaporative emissions systems) and stopped making vented fuel filler caps.
Anyway, if you're having trouble with vapor lock on your Dodge truck, you're best bet is to just swap it to a thermoquad so you don't have to modify throttle linkage, etc... You probably already know that you can get a base gasket that helps insulate the fuel bowl (two designs, one is open under the fuel bowl, the other closes off the gap under the bowl) but they don't always work and may not work at all on a Dodge for all I know. I like to block off the exhaust crossover in the intake, that seems to help the most, but then you also have to convert to manual choke, which I prefer anyway. The older 4MV Q-jets (up to 1974 in cars and 1978 in trucks) are less prone to vapor locking than the "modified" M4MV Q-jets (1975 and up in cars and 1979 and up in trucks), but the later ones have much larger fuel bowls and more adjustments so the're better for performance.
The 1986 k20 suburban I grew up in had a quadrajet, it was replaced with holley pro-jection, and put back on because the holley ECUs wouldn't last.
My dad claimed that when properly tuned there was a 1 or 2 mpg difference between the q-jet and fuel injection.
Quadra Jets are now being sold on Ebay as they are made in China and the average price is $250. If they are an exact copy they are a damn good carburetor. My advice would be to use a a phenolic resin or plastic one inch spacer to keep it cool and a high output mechanical pump to feed it. Use a 3/8 inch supply line.
Anything smaller will cause problems.
Actually a damn good carb - once you figure them out. I ran 'em on all my Chevys, a few Fords, even an IH pickup I had.
Guys forget, at WOT any two carbs with the same airflow and fuel mixture make the same power.
I like that the Q-jets fuel curve can be tuned so close, and the only issue with making big power is the tiny fuel bowl - which there's more than one way around.
Holleys are fine - they're simple and easy, if that's all you want.
I agree ! I replaced a Holley with a stock 1973 Q-Jet from a Chev. Blazer on my stock 1976 Jeep 304 . Much improved acceleration and great sand dune climbing ability !
Bullseye hit about WOT/airflow. What the Q-jet did was improve everything between idle and that so you'd go faster getting to the top.
TONY- Your good, you know what you know. You don't know what I know. Did you know the quadrajet air horns warp which drips gas at the booster and causes idle problems? This is because their made from pot metal, and I would take off the horn, beat it flat with a hammer, and even if cracked, it stopped dripping and ran much better. I did this often in twin engine race boats and cars. Other than that( cheap metal) they were efficient. THERMOQUADS (YOUR FAVES, RIGHT?) Were very expensive because they were made with AIRCRAFT grade aluminum, the phenolic resign bodies DID NOT WARP ( one time there was an engine fire due to a leak- the Thermoquad though in the fire, only needed the idle air bleeds cleaned up in the passenger side where the fire was- the phenolic body was fine to my surprise! NOTHING can be tuned to produce the best mileage AND power than the THERMOQUAD- and their VERY light too! I saw your video years back with a very tragic, highly abused vestige if a Thermoquad with impossibly rusted throttle plates and a phenolic body with a chunk out of it somehow! Can't speak to what the hell that thing went thru, but I have built MANY T-Quads without any such issues. Biggest problem was the primary jet wells epoxy letting go and leaking into the recessed area of the base/throttle plates, causing slow leakage that produced a rich idle- Marine Tex white epoxy kit fixed them permanently (JB weld would only last a few years or so). THREMOQUAD was the PINNACLE if carburetor development for COMBINED STREET/STRIP. We will see with the new Edelbrocks! (Which are based on the avs afb Carter earlier design than the T-Quads, competition and superquads. No other carb EVER had such small triple boosted primaries with giant secondary dumps on STOCK 850CFM. NOBODY. IF more people understood the T-Quad they would be fans. They were that good, but VERY expensive when new, again, the biggest quirk was the jet wells, which the Marine-Tex solved.
Hey UT, John and Ashly in Canada. Just want to thank you for sharing your carb knowledge and passion. I love carbs . Fixed my accelerator pump in Mexico (67 Rambler, 232 2bbl) with a tassle from my girls leather coat and a razor blade and screwdriver. That was in 1987 when I was 21.
Once you figured these out they are great carbs and only hated by those that dont understand them. Pull the secondary dashpot (vacuum pull off) rod and set the air door spring correctly and you have a nice no bog secondary kick in. Vacuum pull off slows down the air door when it has vacuum and is slow to react. Drill out the idle air bleeds and it takes care of the idle issues with bigger cams. The good thing is these came with all kinds of jets, springs, rods and metering holder heights and can be perfectly tailored to any engine.
Bingo! Most people that Hate Them Don't Understand Them.
Better to make the pull-off open at the proper rate.
JB Weld has always worked for me to eliminate the well plugs leaking. Although, using JB Weld that will hold up to modern ethanol enhanced fuels is imperative. Also, some of the later Q-Jets were sought after by street guys due to the larger fuel bowls. You’d know these in particular, as the air horn has more screws attaching it to the fuel bowl over their older derivatives. (Think just prior to the CCC carbs.) Those had double vacuum breaks, and the bigger float bowl. They were the Chevy hot rodders dream carb. I believe they were only made for a couple years before they all went CCC.
I've only ever had trouble with jet wells leaking on the very early Q-jets. I've seen lots of the later ones "fixed" with JB weld that didn't even need it and the epoxy turns brittle after several years and flakes off anyway. The only way to permanently fix leaking jet wells is to remove the lead plugs and tap the holes, then use set screws and put epoxy on them like pipe dope.
@@livewire2759 that's exactly what I do. But I use aluminum rods and thread them, cut to length and cut a groove on the end. Use extreme high temp thread locker on them.
Pos carb needs glue lol
You can run a mill slot drill down beside the float bowl at the rear. Cut both sides and it opens up another 40% volume for the float bowl. Here in Australia, we couldn't run a NASCAR mechanical pump on RHD 1971 -84 Holdens with power steering, so I ran a mechanical pump with a Holley red pump working off a kickdown switch and relay. No starvation in hot Aussie summers and it was more reliable than a Holley blue pump. Cheap throttle shaft bushes are 30 cal (30-30 or 30-06) cartridge necks cut off and locktited into the baseplate. My Hillbilly cousin taught me that. For mild street cars up to 1.3 HP per CU/IN, they have no peer. Still the closest carby to fuel injection.
Love the bushing idea.
Watched a super stock Camaro run 9's with a Q-jet, impressed me to no end.
Are you sure it wasnt a Holley carb that ran that fast
@@paulgill5813 I'm positive, it blew me away when I walked up and the hood was open, there sat a quadrajet. Of course the motor was worked on, had state of the art heads, cam, etc.
My favorite carb!!
I had rebuilt one for my car way back when, and the cold-started engine ran at exactly the same idle speed as the warm idle!
Had those on my first 76 Impala 400 small block. Got 20mpg if I stayed out the throttle and made the coolest sound wide open with the air cleaner top flipped over.
Fellow lid flipper. had my all stock 72 k20 lid upside down always howled up the hill to the scrap yard with a load of junk.. miss them days of being a poor kid with a cool truck
I have an original Q-Jet on my 69 Corvette with a 350. Just put a kit in it. Works fine. 50 years old and no problems. What's not to like! 😎😎
I love the Q-jet. I always used air/fuel gages, vacuum gages, timing lights to tune them. I also found that a fuel pressure regulator helped with a lot of the fuel issues relating to heat and small bowl size.
The 4X44 guys like the QJ because it works as greater angles.
My father could make a quadrajet carb produce he loved them too. He wasn't a professional mechanic but so many guys dropped carbs by the house for my dad to work on. Besides as you said they were the best moderate to higher performance carbs out there and they were cheap. After he passed in 06 I had boxes full of carbs and parts and I'll tell you I had guys begging for what I had.
In 67 & 68 the intake manifolds had the exhaust heat crossover also going through under the base of the Qjet and used a thin gasket with the stainless steel thin heat shield. The old 2GC actually had the exhaust running through the base of the carb! In about '69 they deleted that system. Chevy did make a Qjet aluminum heat shield too
Interesting theory about the fuel spec change. Less volatile fuel reduced passive emissions, part of it was emissions related.
I think that is partly the reason why GM went to the 1 piece rear main seal after 1986 , oil leaks and fuel vapors were then included as part of the total vehicle emissions
when i started running a Qjet on my 1966 GTO i had to rig a fuel return line to the tank to solve the vapor lock . this was about 2004 before that i had ran a holley anda 2 bbl without vapor lock problem.
@@repete2362 i don't know about the earlier ones but I'm sure 68 and up came with higher volume fuel pumps. It had a 3rd line on it for return. You could always tell if someone swapped out there 2bbl for a Qjet, the fuel pump only had 2 lines.
Yeah I hear ya,. Back in the day those quads made my little chev 265 and 283 go like stink compared to the stock carb. Never had a problem with the heat . That sound was great.😂😂👍
Quite possibly the best carburetors ever made. An engineering marvel!!
I think you're right, but" Quadrajet is either great! or it sssuuucks and needs to be dipped and rebuilt.
As for performance I have seen some that were amazing and beat every thing out on the road.
I had one on a firebird formula that should have never been able to do what it did.
Then again I had one on a chevy truck that many times I wanted to take a hammer to it.
But all around a Quad is a awesome carb and I will run one and be happy with it.
Actually, it was a super thick fiber gasket.
They began installing essentially a heat barrier to keep the carburetor cooler.
They also added a return line on the fuel pump
@@christianperspective9527 I remember early on that a lot of vehicles did not have internal pressure regulation in their fuel pumps, and when I would install a newer pump on a car, I had to rig up a return system to the fuel tanks.
I had mine on an FE Ford, and I made an aluminum heat shield that want out and up to keep the heat away and always block the heat passages in the exhaust ports with a thick piece of stainless steel in each sides port shaped in the bowl and Devcon to seal the bowl and a thin piece of stainless in the gasket passages installing it. On an FE half of the head is the intake. I liked the Holley SD and used a homemade plywood adapter where I started a spreadbore shape and sealed the adapter with a gasket and it was matched to each with the heat shied and I wore that carb out, daily driver street racing, it was perfect!
I love Quadrajets. I pick them up whenever I find them, dedicated manifolds too. I used to run a '71 big block Camaro in D Stock Auto and learned early on how to make them run. It's not difficult but they can be made to be fully adjustable and few people know even the air door spring (opening) rate is adjustable. Once set up they just put down the power to the road, I especially like the 800 cfm models. The well plugs are easily fixed, there are kits to rebush the throttle shafts and you can modify the carb top to allow access to the primary metering rods and they can be adjusted with a large tire valve tool. I've had my best luck with an electric fuel pump and regulator set to 8psi. Doesn't matter if it's a 455 Pontiac, 500 Caddy or a stroked 510 ci big block Chevy, even a 283 they just perform and I have done a head to head with a Holley 750 and especially on the street you can feel the difference and smoothness of the Q-Jet. And yes, I have a couple Thermoquads sitting on the shelf, one off a '73 Charger with a 400 and the other off a '72 Polara cop car with a 440 just in case I run into a Mopar project.
I couldn't agree more ...the Qjet was the everymans carb with performance potential that was overlooked by 90% of street guys .
Getting that air door tension right was one of the reasons so many hated them, or used the "quadrabog" moniker.
Few amateur tuners really figured out the secondary metering rods and airflow through the upper doors weren't directly coupled to the rest of the throttle linkage, but depended on that spring loaded shaft opening at just the right rate.
I always liked the 850 Buick Stg1 carb and they actually made a 1708 replacement for the Buick Stg1 to run in NHRA class for the 430 and 455 cars. The Pontiac 400/455 Qjet was 800 cfm and had slotted secondary air valves with pullover secondary enrichment that as soon as the throttle blades moved it pulled fuel until the air valves began to open and lift the hanger and rods.
I have found that a trans cooler between the pump and carb solves the heat soak issue. It can be 95+degrees and the carb is cold to the touch. Also insulating the fuel line from the cooler to the carb is a good idea.
@@geosradiomusicalstuff3124 yep.
@@geosradiomusicalstuff3124 I will add that I have only ever used a stock mechanical pump while doing this. I would guess that a trans cooler can handle more pressure but I'm not sure how much.
Three guys came to my garage one day about 10 or more years ago from the then known as Nashville Auto Diesel College. One of the guys was a regular visitor and familiar with most of what I was doing. Upon coming to the bench one of them looked at the to be assembled piece and asked, "Whats that?" I looked puzzeled and said to the group, "Your kidding me, right? Don't they teach you about that at NADC? (They were in school uniform as they were on lunch break.) It's a Quadra Jet carbureator.", I explained. There was a brief pause followed by the question, "What's a carburetor?" True story. This was a great video and thread like none I've ever seen!
Thanks Tony for throwing me back in time. I will never forget the 70 Chevelle SS I had with the LS6 and cowl induction. I think the rochester was the 800cfm version. When the 4 barrels opened up the sound coming through the cowl induction was unreal. Thought it was going to suck the windshield out of the car. I had a buddy that did some modification to his on a 69 vette BB that supposedly got it to flow 1000cfm.
@@racer44x Actually you are correct the engine had a holley on it originally. The manifold was a square bore also. I did not have an adapter but did have a spacer. So dremeled out the secondary side of the spacer on the quadrajet side to fit. So many years ago. The town was 3300ft above sea level and at the time just could not get the holley to run right. Also would eat so much fuel barely had enough gas to get to the next town.
I don't believe it could ever flow that much or even need to but good story
The best video at the table is the one where Kathy is trying to talk Tony into doing videos, bag of chips flying, Tony runs and tries to hide behind the garage only to be convinced by Kathy telling him they could make money, Tony says I like money... classic!
I love quadrajets, good performance and very reliable and good mileage.
Trash. Had 10+ quadrajunk carbed cars all got 5mpg on 10 year old cars. When they ran or weren't on fire.
@@thefinalroman Strange, I have owned many cars and trucks with 350's and 305's with the quadrajet and not one of them got bad mileage. The worst quadrajets were the ones with electronics on them, they were TRASH! Unless you got a 454 big block hauling a load you aint seeing 5mpg with a clean quadrajet. I will always be a Mopar guy though,haven't bought a chevy product in around 25 years.🤣
@@u.p.tinkering Every quadrabog I ever had was from the 80's so it definitely had the emission crap on it. Air pump and various solenoids + huge vac diagram.
For some reason every other 80's car with all that emission crap ran fine. Toyota,Honda, even K cars (Holley carbs 2bbl)
@@thefinalroman Yeah those ones really did suck. My favorite car was a 83 Turismo 2.2 with the 5 speed. It had the Holley 2bbl ,I really loved that car and ran it for years into the ground. To find one of those Turismo's now is near impossible. It was the black and gold accent one.
Holleys need constant attention. Edelbrocks are a bit funny. The quadrajet is a set it up and no hassles if you set them up right. They are not repeat NOT performance carbs. They are street friendly and if you get your timing set right, and secondaries where they can drop the venturi flaps down they will light up like a rocket. They work. They are reliable. I love them. Easy to rebuild. Easy to set up. Like you said though, the bowl will dump out. Heat soak can be solved by restricting the exhaust crossover.
I have a 1966 Olds which came with a Quadrajet so 1967 was definitely not the first year for the QJ. In fact, the 67 Olds came with a completely redesigned QJ compared to mine (vacuum damped secondary's rather than fuel dampened) so by 67 they were already onto a second iteration of it. Great video though, love the review.
In '66 they were only used on the 396 big blocks, but in '67 they started using them in almost everything, except trucks which didn't get them until '69 or '70.
Again I have a 66' Olds with a QJ. It came on it from the factory ll
@@livewire2759 oldsmobile used it on almost every engine they produced in 66. Look up the 66 olds toronado!
I learned the QJET on my Toronado. After replacing rocker arms, pushrods, and intake. First fire it had a huge backfire out the QJet and split it at the secondaries opening. I loved cruising in it. I liked the kick of the secondaries opening. 800cfm QJet on the 455 Olds was pretty fun. It was the first not lawnmower or tractor carburetor I rebuilt. Will still hold a place in my heart even though I'm 21 and only had the QJet for a year and a half.
They started using a thicker gasket under the carb and it solved the heat soak problems
The super early ones, 1965- around 67-68 used a heat passage directly under the carb base and required use of a thin, metal sided gasket and those would really heat up, sometime in the late 60s they quit using that whole system and started using the thick 1/4in gasket with no heat passage which greatly reduced carb temp.
I knew there'd be some way to easily engineer out the problem. I love stuff like this.
Uncle Tony thank you so much for taking your time to get online to explain carbs it's been very insightful
The moment I saw those wee primaries and honkin great secondaries I knew I never rebuilt one or owned one. But I rebuilt many earlier 4bbl GM carburettors and noticed that people would quite commonly lock the secondaries out to improve gas mileage. So based on that experience I think GM did a great thing to do an asymmetrical design.
FYI: That quadrajet that you have there was built by Carter. QJets were in such demand at one point that Rochester contracted Carter to help keep up.