"But What About The Quadrajet?". The Good, Bad And Ugly Of The Worlds Most Common 4BBL carburetor

[@jamesgullo8240]

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

[@buzzwaldron6195]

QJet around to about '91...

[@mindeloman]

Just put a Q-jet back on my grandfather's 72 C-10 pickup that is show condition. Back around 1980 he put a Holley "Economaster" on it which was a direct bolt-on replacement for the Q-Jet. This year, 2024, that Economaster was having problems. I sourced a year correct Q-Jet for the truck. For the first time in 44 years, that truck had a Q-Jet back on it. And that 350 chevy came alive!!!!!

[@davidpotter7484]

@@buzzwaldron6195 Factory replacements were still being made a decade after the last one rolled off the line.

[@buzzwaldron6195]

@@davidpotter7484 - Yeah, Edelbrock made (expensive) QJets before moving to Carters...

[@davidpotter7484]

@@buzzwaldron6195 I've never heard of an edelbrock quadrajet

[@haworthlowell805]

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

[@toefield251]

Exactly. You can also drill cross holes in the fuel feed tubes and epoxy the fuel transfer holes above the air valve and drill holes below the air valve. There's so much more but too much for a comment. You can modify these carbs to really run.

[@JimSix-jo6hf]

yes even on daily drivers those did not flow much fuel

[@johnnystephens6329]

33 years running the Q jet. Fantastic carburetor

[@NoralBlundell]

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

[@superrodder2002]

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

[@hotrodray6802]

Kinda like vacuum secondary springs.😮

[@EazyD_PFT]

i am that noob. but then again, I havent set it up at all.

[@terryzeissler4199]

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

[@waylinbuerger2753]

I don't overtighten my mounting bolts on my Quadrajets or other carburetors because I'm a seasoned tech. Commonsense goes a long ways. I know what you are exactly talking about because I have seen several Quadrajets warped on the top of the carburetors and grooved up deeply from the heads of the bolts sinking into the aluminum from people way overtightening them. I'm like "Damn, they destroyed a nice carburetor, what in the he__ were they thinking!"

[@Sabe53]

@@waylinbuerger2753 They weren't thinking.

[@selfdo]

How many warped Q-Jets (and other carbs) got through those "Maquiladora" carb rebuild factories?

[@michionwheels]

Some say as long as the parts are warped equally it's not an issue. But when I build one I always use an "unwarping fixture" that I have made especially for the quadrajet. It's basically a set of two thick plates with reinforcements where I put the mainbody in between.Then I carefully bring it up to temperature in the oven and tighten the screws which clamp the plates. I've seen this a long time ago in an old book.

[@Sheisthedevilyouknowwho-ft9we]

Amazing , to think, at least one way of looking at it, even the average 'shadetree mechanic' of the last 60 years, you would think that most of them would stop themselves from overtightening because you realize the carb is aluminum, and I'm no expert mechanic. But, I'm sure most of us have done boneheaded things that we look back and see in 20/20 later on

[@aaronkeiser6349]

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

[@stevejohnson6858]

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

[@genehart261]

There was a guy in Glendale, CA., Erik Avril, a Quadrajet legend. Richard Johnson at Fiasco Dyno Tuning as well.

[@stevejohnson6858]

@@genehart261 Right. There was another guy whose name escapes me now who stock class drag racers would send their QJs to. I had a cousin who ran a Caddy in stock class and he sent his QJ to the guy.

[@jeffie8696]

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

[@ThomasDahlmann-ob3rw]

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

[@STARSHIPTROOP]

QJet : the reason for the upside down lid

[@davehad-enough2369]

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

[@hotrodray6802]

He WAS a Ford guy

[@harrywalker968]

@@hotrodray6802 ford guy. because other company,s use ford parts, so i bought the original, not a made up something.. thermoqauds were used for drag cars in the 70,s. nothing was better, they suit any cfm..holley too much fkng around. qjet, rubbish.. all i need for my clevo to go is a decent cam. chev need a speed shop & bank details.. fact.. i also own a dodge challenger, 340 r/t.. thanku.. i do have a bit of chev, the rear disc on my highboy, 75.. chev are like volvo, good for some parts.. not many..

[@455buick6]

Anyone putting a 650 CFM carb on their V8 is just wasting time and money, not enough cfm to do anything except make it barely run🤦

[@fuzzyfireman1]

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

[@toefield251]

Yes indeed. I was thinking about that but didn't have the balls to comment. Should be the top comment highlighted, I think it was an Oldsmobile 455.

[@Joesmusclecargarage]

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

[@Theblueghost69falcon289]

You put street and street. Do you mean street and strip?😅

[@Joesmusclecargarage]

@@Theblueghost69falcon289 Try reading it again. I said street, and street/strip. Get it now? Maybe get an 8 year old to help you with the words that contain more than 3 letters.

[@Mikefngarage]

easier to tune and better for the street. you would not eat up so much gas driving on the street. And you had the power when you need it. High rise manifold keeps the heat down a bit.....Carter carbs IMO just dont work as well.

[@yafois988]

Exactly my experience, Once setup , I said "Mine ran like my Honda Accord EFI!” literally the second day because the first day I JUST could Not believe how well it ran, and had to overcome Untrusting Bad reputation the “idiot stoners” put out against them. For 50 years. I was so amazed how it performed reliable all the time.

[@adampatterson707]

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

[@britjohnson1990]

Try a thermoquad! They came on cop 318s and you can score one easy. Just adjust the air door secondary spring tighter if you grab one off like a 400. Its a great carb

[@warrenlewis3977]

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

[@gt-37guy6]

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

[@T.Tuxedo]

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

[@jasonmartin8836]

Oh that sound. Will always love it.

[@mikecrawford5331]

Awesome sound when they opened up.

[@DocZoidberg549]

Carburetor pron. It was f'ing epic.

[@randyfrieler5524]

Used to turn the air cleaner cover upside down on my pops 73 pickup, would HOWL when you kick it down.

[@jasonmartin8836]

@@randyfrieler5524 absolutely! I'm thinking about picking one up again and doing the same

[@Matthew_Lloyd]

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

[@jasonrackawack9369]

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

[@jimanderson4981]

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

[@hawkuser604]

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

[@crsp76691]

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

[@gt-37guy6]

Same with my 455 Buick, and my Pontiac 400 I had before that. I was getting 15 MPG from Tempest 4 speed Ram Air Iii cam. 3:31 12 bolt posi if you ran it "nice"

[@malcolmboynton7652]

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

[@morgangallowglass8668]

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

[@alanmeyers3957]

Then your not a carb guy.

[@sategllib2191]

​@@alanmeyers3957sounds like he is to me lol

[@morgangallowglass8668]

@@alanmeyers3957 , seem to do fine with the ones I like.

[@powerwagon7811]

Maybe Mikuni vs Keihin , Bing probably not even in the discussion.

[@morgangallowglass8668]

@@powerwagon7811 , not a vintage BMW fan?

[@aprules2]

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

[@nickbruni8041]

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

[@robv.o.1777]

I used to drill the enrichment ports for the secondary air doors. It got rid of most of the bog. Using K metering rod holders with AK rods. Worked really good at High altitude, with using 69 Jets to lean it out

[@enduser6982]

@@robv.o.1777 correct the bog issue is after a cam change, the primary vacuum plunger spring needs to be weaker to overcome the lean issue on WOT mode

[@gustav25897]

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

[@MattsRageFitGarage]

Yep. I have two of those summit carbs, one I've had for 11 years and its been great. Driven year around, never a problem with either of them.

[@ProjectFairmont]

4100 is the simplest 4bbl ever. The 4300-50, not so much haha.

[@makkepuu]

I still have nightmares about the Motorcraft 4350 on my 460

[@MattsRageFitGarage]

@@makkepuu Far cry from the 4100 lol.

[@Mr.Saltwater]

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

[@FrankF-vp4pt]

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

[@DocZoidberg549]

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

[@workingcountry1776]

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

[@GB-zi6qr]

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

[@dr.detroit1514]

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

[@mrweeby1961]

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

[@39KHall]

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

[@falcorthewonderdog2758]

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

[@mattlitchfield221]

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

[@williamjohnson5030]

I had the same car with a 262. Swapped the 2bbl for a Qjet and cast iron swap meet intake. Experimented with different jets and metering rods and got it running great. Learned a lot and had tons of fun.

[@mattlitchfield221]

@@williamjohnson5030 Same engine mine had when I got it!!

[@MichaelCummings-ry3pb]

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

[@gustav25897]

Pontiac ABSOLUTELY had heat soak problems, at least in the southern states. Their problem stemmed from the steel line routing though, not the manifold getting coated underneath with hot oil. The Pontiacs (at least in stock form) also had a heat crossover that was often TOO efficient in heating the intake, which is why we usually installed block-off plugs in the gaskets to block exhaust flow off most of the time. I LOVED my GTO and Trans Am, but i ALWAYS used a phenolic spacer, blocked off the crossover, and wrapped my fuel lines, or sooner or later, it'd vapor lock, At least in the mid 80's in Central Florida. As to the separate intake / valley cover, it certainly made for some quick intake swaps, that's for sure.

[@MichaelCummings-ry3pb]

I never had a heat soak. Lived in Savanah GA. Had a 67 GTO and SD 455 Trans Am. I could see a possibility if you had the cast iron intake.

[@SweatyFatGuy]

@@MichaelCummings-ry3pb I have run iron intakes since 1985 on my Pontiacs, with Qjets and the crossover not filled, only have one set of heads with the crossover filled. I never had a problem with vapor lock and I didn't do anything special to them. Nebraska gets just as hot and humid, if not hotter than the south does. I was stationed in South Carolina for a total of five years, and Nebraska weather is far more harsh.

[@rollin19]

Ever heard of an evap canisters? Introduced to GM cars in 1971. Guys break down on the hgihway in the summer because they dont understand heat soak. The evap canister works!

[@rollin19]

I had heat soak issues a bunch of times,when it's hot outside,I didnt have my evap canister hooked up,once I hooked it up I drove in 88 degree weather for miles,shut car down,started right up.

[@setha360]

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

[@superman20029]

Where did you find it?

[@anthonyrowland9072]

It's the thinking man's carburetor.

[@johnnyforriester7325]

It's the working man's carb because you was always trying to fix the leaking plugs or building a engine because it leaned the engine out and burned pistons and valves.

[@SweatyFatGuy]

@@johnnyforriester7325 in nearly 40 years of running Qjets and almost 20 years of converting them to E85, I never had any of those problems. Those kinds of things happen to people who don't know anything about carbs, they should stick to E carbs that they can't screw up.

[@keithhays429]

I've recently become a big fan or your channel. I'm in my mid-fifties and have been a mechanic for about 38 years or so. I am learning so many little things from your videos and they are much appreciated. I also love your down-home demeanor in your videos. I am an old Ford/Merc guy and thought you'd appreciate this bit of trivia. Ford/Merc actually used the Quadrajet (a 730 cfm I believe) on the 429 CJ only. (not the 429 Thunder-Jet or the 429 SCJ). I understand it was for emissions purposes to get away from having to use a smog pump, but not sure about that. They were used in the Ford Torinos and Mercury Cyclones in 70/71? with the 429 CJ. You've taught me a lot of useful knowledge so, I thought I'd share that just in case you didn't already know! Love you videos! [

[@michaelsullivan2361]

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

[@don2deliver]

Having just one Carter AVS carburetor for 2 enduro stock cars. I had a spread bore manifold on my 400 B block Mopar. So I rebuilt the carb that came on the manifold, a thermoquad, it was dying out after it got warm. I traced it down to porous plastic floats. Once I put new floats in, it ran flawless.

[@mattkurtz8549]

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

[@tarstarkusz]

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

[@doglegjake6788]

I sure hope this dude is making the money he deserves

[@googleusergp]

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

[@Oxmix66]

As someone who has been rebuilding carburetors since 1965 I totally agree with you.

[@anthonyrowland9072]

That, and someone decided they were junk in 1997 because the one they had that hadn't been touched since 1981.

[@googleusergp]

@@Oxmix66 I get the same response from people in the small engine world. "Why do you like Tecumseh engines? They are junk...". Well I don't know---I've pulled several off the curb, did the proper maintenance and TLC that wasn't done to them with the previous owner and they all run like new. Wonder why.....

[@googleusergp]

@@anthonyrowland9072 Indeed.

[@SweatyFatGuy]

@@anthonyrowland9072 I found the same thing, also get the guys who say pull that 400 or 455 Pontiac out, put in a 350 chevy, and you'll go faster for less money, and of course they also say put an E carb on it. They sure do get upset when my iron head Pontiac with a factory intake and Qjet turning a 3.08 gear outruns their aluminum headed sbc with an E carb and 4.56 gears.

[@carlpreston1680]

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

[@JamesCat-qx6sb]

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

[@oldblueaccord2629]

Thats a cool tip!

[@fishgeralding9224]

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

[@paulherbert5548]

340 Darts were hard to beat.

[@A_friend_of_Aristotle]

I loved the QJ's I had on my cars as a kid. They were easy to work on and easy to understand. The heat and fuel volume weren't my priority back then...I didn't race or push my cars like friends did. I discovered the Edelbrock AFB and realized it was better. Still, after years of fiddling and adjusting, I solved all of my problems by switching to fuel injection...😁

[@donaldfrederick1557]

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

[@doctorcountersteer6580]

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

[@MartinRanger65]

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

[@joeayers3777]

It's Holley.😂

[@BrandonLeeBrown]

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

[@c.r.parish5908]

I have a Holley 585cfm carb original to a 1965 396. Used it on a well built 327 with good results. Excellent throttle response , stopped pulling hard at 5500rpm.

[@roberthollinshead2325]

All the high power chevy stuff had holley carbs because they worked better for that application. In 1966 some of the 327s had an AVS carb that worked really well too for that hydraulic cam engine. When put on a 283 they worked really good too.

[@theshagggy6109]

Thermoquad is JUNK lol it takes 4 of them to get one to work properly. I had to switch the intake because I was tired of the pain and suffering of that thing. So Edelbrock/Carter was the way to go

[@donharvey8823]

Was​@@theshagggy6109

[@donharvey8823]

Did NOT send that

[@als7594]

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

[@richardmorton1310]

Loved the sound of those big secondaries opening up.

[@BillyLintzenich-wf7sk]

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

[@craigpennington1251]

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

[@tdog6437]

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

[@benrossbach6501]

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

[@ronalddimond3752]

Thank Tony. My 1977k15 still has the QJ on it.

[@gumbyhunter]

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

[@olskool3967]

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

[@tommym6335]

Yeah, one of my old dual-plane Edelbrock intakes has a factory notch in the dividing wall to accommodate the Holley 3 Barrel one-piece secondary butterfly.

[@fasst5511]

I started rebuilding quadrajet carbs around 1970. I think they are great if they are adjusted correctly and sealed up where they were prone to leaking. My favorites were the really early ones with the divorced chokes. Also they seemed to be able to supply enough fuel for the Buick 455 Stage 1s and the Olds 455 W30s of that era.

[@Tepictoton]

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

[@jimolson8424]

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

[@JackF99]

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

[@JP-jq1qx]

I was going to comment the same i figured he just misspoke

[@jeffreyrutledge1654]

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

[@willymccoy3427]

My all time favorite carb. When it's set up right.

[@Rick-o7d]

My truck,396 with the quad, switched to 454,put that carb on my 454 back in 1985, im still using it, drove my truck this morning, to get a load, still going strong, not racy, took off the holly,its a very dependable work truck just for work

[@Bobschoppshop]

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

[@bullittboost6046]

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

[@yambo59]

I loved the Q-jet on the street for the amazing sound of its massive back barrels especially on a big block nothing had the deep roar of a Q-jet, you could hear one sucking air with an open air clear two blocks away. Again for the street I found all I ever had to do was replace the well plugs with the oringed aluminum plug repair kit to stop leaking, replacing the stupid foam fuel float with a brass one was a must, replace that bronze filter with a regular paper element that lasted much longer or just throw the factory filter away and install an external one - and heat soak was almost eliminated on the street with a thermal intake spacer that helped with heat coming up from the engine.

[@genehart261]

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

[@alanmoore78]

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

[@alexd.3246]

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

[@mostlypeacefulmisterputin]

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

[@1979gmcummmins]

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

[@SE-me2pt]

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

[@ericwilson2585]

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

[@britjohnson1990]

Good job. Get that thing off the mopar its heresy :)

[@tickie1]

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

[@williamledford5680]

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

[@Chodaboy65]

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

[@keithroute8906]

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

[@americanpatrol4603]

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

[@paulhellwig8120]

As an olds / cad gm Mazda dealer mechanic lots of q jets the old tune up guy was always replacing them ! I grabbed every one i could get my hands on so I had all kinds of jets , metering rods , power valve ect loved those carbs easy to tune without pulling off.

[@gustav25897]

Especially if you have the air flap spring adjusted correctly, which most people didn't even know existed.

[@randywilliams4325]

Buddy had a 77 Trans Am . We cut the back of the hood scoop open . You could really hear the q-jet open up on that car

[@selfdo]

By that point, the 2-barrel small-block GM engines were so "wheezy" and underpowered (110 Hp out of the Chevy 267, and 125 Hp out of the 305, both with that DuoJet, which replaced the 2GV) that it was a lost cause.

[@SpecialAgentJamesAki]

Also the verajet, a qjet cut down the middle with one primary and one secondary. Always wanted to try one on a v8.

[@louisrauzi3872]

Can never beat the sound of the secondarays opening on a qjet.

[@dustinbowen6411]

I used to race in a street stock circle track class that required you to use the stock type carburetor that came on your car. That meant quadrajet for 99.9% of us. I found one that was one of the early emissions carbs and it had a chamber on the passenger’s side front connected to the bowl that was about as big around as a stack of half dollars where a secondary metering rod, jet, and the diaphragm that ran them was housed. I blocked off the jet and removed the rest and had the extra space for fuel. It was made early enough that it would use the old style jets from the earlier performance carburetors. They changed the threads in the mid seventies on the jets. I never had a fuel starving problem.

[@Geoduck.]

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

[@mitchharper_rule62]

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

[@GlenJS]

I have a q-jet on my 78 Suburban, and I know that most people have never taken the time to find out how to fine tune them. I like them and I agree that the Thermal Quad is a much better choice. Cost constraints that I have made my choice for the q-jet the option. When I was putting this engine together the guys at Summit Racing said that they did not have any Thermoquads or anything in a spreadbore except the q-jet. If I could change it, then I would and the cost for a person on a VA Disability makes it a very expensive choice. Also, when I was at the GM Training Center in Tigard, Oregon they stressed that anything over stock needed a heat spacer between the carb and the manifold. The exception to that was the overhead cam Pontiac six cylinder.

[@bobnankervis9722]

In the late 70's and 80s, I rebuilt and repaired Qjets for my customers as well as for the other automotive shops in my area. If you understood them and knew what you were doing (heat shields. JB weld the main wells, brass float swap, etc.) you could build what I believed to be the best overall street carb for your GM. The small primaries (higher velocity) in conjunction with the metering rods allowed for excellent fuel mileage. However, If you don't already own one in good condition (throttle shafts tight etc.) and need to purchase a carb and an intake manifold for your project just buy the AFB (Edelbrock) and call it a day.

[@dongeorge4037]

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

[@jamesrogers5783]

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

[@chancecarpenter5820]

The secondary’s pull fuel from the wells behind the primary’s. There’s a small hole in the bottom corner that has to be cleaned when rebuilding so the carb can deliver fuel from the main bowl.

[@pl7868]

LOL thx for the video , my current setup on a 283 stroked to 354 in a half ton has a breather with two 5 inch snorkels piped to funnels on either side of the grill for a real cool air setup , if you look at any older gm truck the factory already cut the holes for the funnels for you , it's a daily driver i don't race it but have never had vapour lock issues , i take the flap for the choke off so that solved all choke issues , it starts fine even below zero ( i live in canada ) for me it's a simple no nonsense carb i can live with but i have been running them for fifty years you have to learn the ins an outs , if i was racing it would be a big holly but those small primaries on the qjet get me almost 20 mpg on the highway , that's hard to beat in a 4000 pound truck

[@cammer68oliver2]

Yeah, I rebuilt a quadajet on my dad‘s 78 Chevy K-20 four-wheel-drive pick up. First one and the only one I’ve done so far. That carb is a pain to rebuild. Has internal linkages that you had to get right before you dropped the lid on. But I did it. The bad thing I heard about the quadajets is that the plug in the bottom of the carburetor can sometimes start to leak and drain fuel into the intake making starting the engine a nightmare. But my dad is happy with it. It runs good for him now. Keep telling him to get something else but he won’t. Lol.

[@matthewewing663]

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

[@Frank-sf1wh]

I bought old Plymouth once that came with an AFB, I had problems doing corners with it due to fuel starvation. I changed it to a Rochester 4GC that did a fabulous on corner and straight line too.