The biggest mistake people make with the quadrajet and the thermoquad is the secondary air valve adjustment. They seem to think you want it to fall open as soon as you get into the secondary's. Not the case. You need the correct tension on the spring so the vacuum has to pull them open. Otherwise you crack open those huge secondary's and the vehicle falls on its face.

@nellyfarnsworth7381

4 жыл бұрын

You are 100% CORRECT

@thatbiguy1975

3 жыл бұрын

i was 16-17 when i learned about that spring on the secondaries. a little helped so you bet i sprung that way loose! all but hit my nose on the windshield when they snapped open and dumped a pile of fuel into the engine. slower learning curve for some of us but as long as you survive and learn it's all good.

@larryhutchens7593

2 жыл бұрын

@Peter Lockhart I have heard so many stories about the spring adjustment thing that it is getting ridiculous. The little spring has a specific preset tension & has little to do with secondary air valve operation. The choke pull off is the controlling factor by limiting the vacuum bleed off in the actuator.

I've watched my dad Rebuild alot of those Quadrajets he was trained at the GM school in Fairfax VA he also taught me how to rebuild the Turbo 350 and 400 he is 82yo now and is still helping us 4 BOYS at our EDWARDS BROTHER'S TRANSMISSIONS shop in Roanoke Rapids North Carolina THANKS 😀 Louis R Edwards Jr

@SOU6900

4 жыл бұрын

I may have to give you boys some business 😉. I'm down here in Mount Olive.

@ceciltrane5418

3 жыл бұрын

Always thought a guy who could rebuild, and tune a quadrajet was a step above. Tony confirmed this in his comment about an all out quadrajet will need to be spot on.

@saikothesergal

3 жыл бұрын

My grandfather is religious with his Quadrajets, he has six put away in storage and one on his 78 El Camino with a 350 from a z28 camaro. It may not be fast, but damn is it reliable and smooth. He's used that engine with that carb for over 30 years. over 300,000miles

I love the Quadrajet and learned them inside and out from my dad in the 60's and early 70's. for a man who later in life would get flumoxed by the TV remote my God he could rebuild a Quadrajet with his eyes closed!

Thanks tony for giving the Q jet some love. The biggest issue I've seen is that most people don't understand how a basic carburetor works. They know bits and pieces but not the big picture. Thank you for your carb basics vlog. Been doing this stuff almost as long as you bro! Any Q jet off any big inch GM V8 will do till around 1977 learn how to ID them. Primary throttle shafts wear out on them all because the are so reliable and give such trouble free service. I do my own throttle shaft repairs in my drill press. That is another reason a guy buys a used one and it won't idle right guaranteed. you fix the idle well leakdown and the worn primary throttle shaft problem now you can tune to your application. Fun fact: ford must have liked the QJET also because they used it on the 429 cobra jet 70-71. Just recently bought a box of QJETS for next to nothing and scored one off a 1970 500 inch caddy! Again many thanks tony rock on bro.

I would be very interested to see you talk about transmissions. Transmissions are oftenly ignored, but I think they are just as important as the engine.

@MrTheHillfolk

5 жыл бұрын

Bunch of fluid and springs and crap in there. And passages and bands and clutches and planetaries all flyin round, and some valves. you press on the gas and tires go eeert. And that completes drunk transmissions 101 for today.

@two_number_nines

5 жыл бұрын

The same goes for the engine. Bunch of rods, springs and levers all flying around in there. You press on the gas and it starts making noises and make the tires go eert. A good transmission is a vital part of the car to utilize the engine. The right engine with the wrong transmission is just as bad as a bad engine on a good transmission.

@willefixit

5 жыл бұрын

the rear axle gears and things spinng around an make tires go eeerrrt.

@rexcars1835

5 жыл бұрын

Rainy days make the tires do that too. That's when all the fast cars come out.

@MrTheHillfolk

5 жыл бұрын

@@willefixit Thats how I got learned on it

I love Quadrajet carburetors, if you learn how to build them, and do the little tricks to them, they will out perform any street carburetor made. I've built Quads for years.

@justinwallace9045

5 жыл бұрын

I'll be honest... I HATED them until my dad showed me how to actually tune one correctly. Now I'm a fan of them.

@mudduck754

5 жыл бұрын

Take a Q jet over a leaky fucking holley any day

@danielmccoy8875

5 жыл бұрын

Amen brother take a Q jet any time since the late 70s..I have a shelf full of them

@mtjeeves1234

5 жыл бұрын

my only problem with them has always been that they're usually toast by the time you get them. No pressure regulation usually. By the time I spend the time rebuilding one. I'd rather just spend 300 bucks on an edlebrock, 15 bucks on a regulator, and never mess with it again.

@GlassTopRX7

5 жыл бұрын

No they wont, not for making power, might be the most reliable workhorse 4bbl though.

I always let people call them the quadrabogs and quadrajunk and offered to take them off their hands after they bought their holley. Got me a good supply of rods & jets doing that. Its amazing how wide a range of parts you get doing that from seemingly similarily equipped cars.

@JohnSmith-bx1mp

5 жыл бұрын

There were plenty of variants,due to many applications,Very handy for tuning.I still have several in inventory.

@MikeLawson-cj4kt

8 ай бұрын

"Rottenchester" is a nickname for them too.

Quadrajets have always been one of my favorites. Your video is spot on. I have rebuilt probably close to 50 if not more. The biggest issues are worn primary throttle shafts and gorillas torquing down the front mount bolts until it warps the shit out of the air horn and main body.

I'm mainly a mopar guy but back in 1972 I helped a friend tune his 1970 350 nova 4 speed car. It had headers, cam, 390 gear, slicks and a Q-jet carb. One night I lost 50 bucks to a 71 340 cuda with a thermoquad because the Q-jet nosed over in third gear as you described. Ah, the good old days! Lol

I love my Rochester 850, does what it's supposed to. Starts nice, drives nice, when you hold it to the floor you can watch the gas gauge move faster than the speedo? Good stuff!

When I watch you videos I sit down and listen like I’m in class right now I’m in 3rd semester

The spread bore design was a much more advanced idea than the ancient square bore carbs. Me as soon as I read up on the the Thermo Quad I decided to try one on the 318 in ny Dart after running a 383 avs I tuned and rebuilt for it. I found a 9800 TQ at the local swap meet in the early 90s for 2 bucks with the electric choke setup and setup for a Chevy. I swapped in a Mopar throttle shaft, rebuilt it, and tuned the jets and metering rods till it felt really good. It went from about 10 mpg on a good day to close to 12 with a street master single plain intake and was silky-smooth through the power band. The AVS ran super clean but had the usual drivability issues they had. I ran that 2 dollar TQ for over 10 years till it finally blew one of the fuel transfer tube o rings, I rebuilt it again and ran it till I found a super low mileage 9801 with the factory Mopar linkage and rebuilt it and swapped it on. I ran that probably another 10 years till it sat forever when I retired the car and lost the accelerator pump. It still ran good enough to drive 5 miles to my new house in 2012 after sitting since 2006, just bogged off the line so wasn't fun to drive. So I need to look it over and see if it's worth rebuilding again. If not I have yet another 9801 that is missing the electric choke and choke plate, but gas never had gas in it and still has all the factory ink stamps on it. I'll probably piece together the old one though as I don't want to waste a virgin carb on a car that is going to mostly sit once I get it running again. I tell people to run a spreadbore carb if they are going to street drive their car. I obviously prefer the TQ, but a good rebuildable Quadra Jet can be found easily and most folks run GM anyways, though my friends brother put QJ on his Ford 390 4wd truck and was quite impressed after I suggested he try one because it would be cheap and run nice on a truck that needs smooth power delivery and better mpg. I have figured out most of the tricks to build and tune a TQ and I even finally found a strip kit for the later solid fuel version, plus I have a bunch of complete carbs from all years and parts, plus I have the secondary air door tool which simplifies adjusting them properly and they do actually run about 20 degrees cooler due to the phenolic resin body. I have actually only seen a couple main bodies that actually cracked and most of them were in motor homes or large late model cars that the engine bay stayed super hot constantly.

Every QJ carb I have ever had always have accelerator pump problems. The spring under the pump vibrates and wears grooves into the body and never works the same again. Just my experience great video

I used to rebuild these carbs in a Olds dealership, the secondary well plug leaked to , I either restate or replaced them. Love working on them, they ran great most of the time

I like this video and agree 100% with Rick Williams. I hacked through my 1992 RS and installed a CCC Rochester Carburetor and CCC System. GM mild cam and the car performs way better than it did with just the TBI, Chevy 350 Swap, and Cam swap. Most Mechanics do not understand how they work as opposed to how they think they should work. Yes... I went through about 40% of every issue. Bogging, Flooding, Air Horn Warpage, Choke, etc; I could not find any mechanic who wanted to work on it. But this $30.00 junk yard carb was going to have to work. I did my research, bought books, searched online, bought the right tools and fabricated two tools( TPS Adjustment Tool & Air Lean Screw Tool), and watched videos. But the most important thing I did ...was to set everything back to factory specs as my starting point. Note: I did have to do some grinding to the air horn with my dremel to get rid of my bogging issue, because of the slight warpage and I had to raise fuel pressure from 4 psi to between 4 3/4 psi to 5 psi. Qjets tend to leak with psi over 5 1/2 psi to 6 psi.

I have had more Quadrajets than I could ever want to remember. I actually really liked using them. My last 4 square body Chevy's have had them. Another informative video. Thank you Sir

I've worked on Plenty of these carburettors and the biggest issue that I come across is that people torque them down too hard and it warpes the top plate spills fuel everywhere

@JohnSmith-bx1mp

5 жыл бұрын

And strip the filter housing threads

@Lauterbach24

5 жыл бұрын

I wish they had made the Quadrajet without the bolts running through the air horn. It would have saved 99% of Quadrajets from warping.

This is to my mind and application the best car channel I have found. This is the on track, applied knowledge car stuff that is actually useful and will only ever cost you what you need to spend to get what you need. Tony is the actual schnit. I’m starting my 1970 valiant hardtop soon (69 dart with Aussie front) and the daily driver build is exactly what I’ve been looking for. Thanks Tony for the breath of fresh air

Gotta love the T/Q. A very mis-understood carb, but well worth the effort if you have the patience. Metering rod change in literally minutes, no fuel spillage. 👍

Thanks for all the vids Uncle Tony. As a young guy who attended tech school this stuff is still alien because no one teaches it, no one cares how it works anymore because they’re “obsolete”. This is great knowledge being passed down. Thanks, from a young hot rodder to and old one.

I absolutely love the Q-Bogs !...they are a bit finiky to adjust but once dialed in, they make a great carb for daily drivers. Lots of guys are quick to swap them out for Holleys and others, and I always ask them if I can have their old Q-Bogs...9 times out of 10 I get them for free.

@rogergoodman8665

5 жыл бұрын

m schiffel : LOL! I've done the same thing for about 20 years! I probably have 50 Q-jets in my garage! My "Holly" friends always laugh & give me a hard time but I like collecting them! I tell them some day that someone restoring a rare car will come a knocking looking for a specific "numbers correct" unit & I'll sell it for a premium price! I have ran the numbers on most of them & have them marked for application(s). Currently none are for sale though. I do have about 20 other brand carbs, in 1, 2, & 4 bbl versions. I want to buy one of the Holly 3 bbl carbs just to have even though everything I've read about them say they are complete trash because their almost impossible to tune. Their so bad, Holly won't even make parts for them anymore!

Makes total sense now. Back in the day, a buddy put a Holley on an otherwise stock '87 Monte SS simply because it was a Holley. It never ran right after that.

@muffdiver777yummy8

5 жыл бұрын

prolly too much carb for the 305

@paulb.2125

3 жыл бұрын

The stock carburetor on a 1987 Monte SS was a electronic Q Jet hooked up to the computer.The aftermarket Holley was a total manual non computer controled carburetor so the computer didn't know what was going on with the engine.

Wow! I can remember a 1978 Ford LTD that had G.M. power steering pump, G.M. air conditioner compressor, and other G.M. parts. It had the 400M Cleveland engine. He also had a radar detector & a speeding ticket for 98 mph.

@timsharpe3498

2 жыл бұрын

Most Ford owners had no clue about all the GM parts Ford used to make their cars work better. Ford was always careful to disguise them.

@slewfoot6608

Жыл бұрын

😂😂

Like every gearhead I know, we would always run around town on a Quadrajet..... A Quadrajet was used on all my street rods, hot rods or street race cars I owned, until time to race time that is! ...... *We would drive to the track every weekend on the Quadrajet and switch to a Holley Double Pumper for the racing* ... My cars were anywhere from a half to a full second and a half QUICKER with just the Holley carb switch! ..... After the racing, switch back to Quadrajet and drive home! ..... *Quadrajet carbs are great dependable mileage miser carbs, but they can't come close to a HOLLEY Mechanical Secondary - Double Pumper!* ............. *Just a side note here for you New Guys* , no matter what Summit or Jegs magazines says, the Holley 600 vacuum secondary carb IS NOT a performance carburetor!

@tabbott429

5 жыл бұрын

I had a friend who swapped my edelbrock 650 for a 750 Holley double pumper with mechanical secondaries. He was a drag racer and tuned the Holley just right for my application. Built 429 Ford in a 72 gran torino. We also put ladder bars on it so it would hook up and not just sit there and roast the tires.

@ken5ism

4 жыл бұрын

Solely depends on what you were driving and how you have the Q-jet tuned. Double Pumpers I believe started out as a full blown race oriented carb and Q-jets were just basically setup and tuned to be factory carbs with minimal to mild performance ? Mild being passing your jerk of a neighbor (from down the street) on the freeway and giving him the finger for stealing your highschool sweetheart.

Had a 1970 Buick gs455.Pulled the Rochester and put in 850 Holley double pumper.Cut over a second off quarter mile time.The Quadrajet just sucked dry halfway down the strip. All my GM motorhead friends had buckets full of Rochesters laying around. They make great doorstops..... Holley ruled the Age Of Carbs. When I bought my new 1973 Trans Am Super Duty from Herrington Pontiac/Buick in Georgia, the dealership was putting double pumper Holleys on the Super Dutys as a 200 buck option with factory warranty. Jesus,that car was a beast... Claimed to be 340 hp by GM for insurance reasons, true hp was said to be over 400.However ,with 12 to 1 Jahns pistons, Edelbrock headers and intake manifold ,big fuel pump and the 900cfm Holley, mine dynoed at 575 hp.

I personally like the edelbrock carbs I can tune them to perfection. When the quad is on it is a beast but they are a pain in the rear 80 percent of the time. Good video.

The Rochester Quadrajet, Duojet and the Motorcraft 2100 was always my three favorite carburetors. With stock engines you could pull a Quadrajet off a 283 and bolt it right on a 400 and run it

I used to race one of these because I was required to, but I liked it. Never had an issue with heat soak or vapor lock. Just add stack another gasket under it, and don't crank it down too hard. Always smooth transition when you stomp it at the lights. If you race it you can pop that top pretty quickly without much trouble. Rejetting at the track didn't require draining fuel either. The leaky bottom was fixed with little brass pipe plugs and epoxy. Will you get the MOST out of a given car with a spreadbore? Likely not, but if your sanctioning body says you gotta use one don't despair.

Love these! BTW, I hope you’re teaching somewhere like a high school or community college because you explain everything very well, so easy to understand and a pleasant personality. Oh and you’re funny as fk! 🤣

I had an edelbrock 750 on my 454 1980 chevy truck. Worked great. Not a race truck but had some performance. The "mechanic" broke the choke and replaced the carb with an 810 quadrajet. It was very smooth. Too smooth for me. Felt like I was driving an older cadillac. I much prefer the edelbrock 750 for my truck. Which I ended up having to re purchase. 👍🏻

One thing he mentioned, was running out of gas at full throttle. That can be easily fixed by replacing the needle float valve. There is a .95 valve that will let in plenty of fuel so you don't run out at full throttle. I had a 76 Cadillac de ville, the 500 cubic inches and I rebuilt the carb made a lot of adjustments but I got it to where I got 10 MPG around town, and 15 MPG at 65 MPG on highway. Not great by no means, but for the car 5,500 pounds, the 500 engine, I felt it did pretty good. I would floor it getting onto the highway, from a dead stop all the way to 100 MPH it never ran out of gas. I turned the air cleaner top upside down so I could hear the carb better too. I love that sound when the secondaries open.

I took apart a Quadrajet once. Went down to Thrifty Auto Parts and bought a Holley 830 double pumper. I was never very smart with carbs.

@joebradley1520

5 жыл бұрын

Yep and your constantly adjusting it aren't you, i

@nhragold1922

5 жыл бұрын

@@joebradley1520 if you are clueless as to what you are doing, then probably..

@joebradley1520

5 жыл бұрын

Racing Prospector no, your clueless to try and convince yourself that you don't, but then again looks like you wouldn't even think a carb needs adjusting anyway even if it did. Everyone and their mother knows hollys are notorious for having to adjust constantly

@nhragold1922

5 жыл бұрын

@@joebradley1520 once again, if your set up is fucked up, then yes I'm sure you need to adjust it constantly. Wouldn't go that route with some you don't know on KZread. You are talking to a full time drag racer and a life long mechanic. I see first hand what works.

@ghost-jesus

5 жыл бұрын

@Malcolm Reynolds the "can't rebuild a quadrajet" statement tells all that anyone here needs to know about your carb expertise.

The old man always knew when I ran the piss out of his '68 Catalina, damn thing would always vaperlock on me when I got home. You would think after the first dozen ass kickings I would have learned not to do that.

@BlackLS1Pontiac

5 жыл бұрын

Hahahaha

@throwingsparks

5 жыл бұрын

Howlingmad Mudduck ...Nah, you were just a few more ass kickings away from learning😂

@mudduck754

5 жыл бұрын

@@throwingsparks and if I could do it all over again,looking back, I wouldn't change a thing.

@ken5ism

4 жыл бұрын

LOL!!!

This is the first time I've shared this, because if you don't do your homework ... you deserve a Holley lol.. The reason Qjets lean out on the top end is the holes for the secondary feed tube bowls are too small. Just enlarge them to fit your needs. I've had the lean out issue and after making this change I go 100 and whatever I want (usually 150) for as long as I want, no problem.

That sound when the secondaries open with a fipped air cleaner lid .... love it

@cruzinezy1968

5 жыл бұрын

Buh-WAAAA!

@scottyjones27

5 жыл бұрын

My grand dad said sounded like milk cow when I flipped the lid on his old 69 Riviera Buick !! 435engine not the front wheel drive junk

@thespiritof76..

4 жыл бұрын

And the passing gear kicks down to second, with glass packs?? Tu-WAAA!!!

You're the only other human being I've heard use the expression "went tits up" to describe a company going out of business. I'm 47 and my Dad used to say that all the time. I say it sometimes and people look at me in bewilderment. Great vid.

I've had good luck with quadrajets. You have to have a guy set your carburetor up on a test engine. They will flow 750 CFM. Once you got one that's in good condition set up by somebody that knows what they're doing they are a set it and forget it carburetor. Also when those secondaries open up they sound pretty cool. Especially when you flip over the lid on the air cleaner. Doo-whaaa! I did have a 780 Holley double pumper I was very fond of. I ran it on a weiand intake, on an LT1 with Pete Jackson Gear Drive. and on a 396 in a 66 Chevelle, on a Torquer, with a 4-speed. It was a greasy sled. Hours of enjoyment.

Lingenfelter certainly knew his way around Q Jets

I rebuilt one from a 1968 Tornado in the late 1970"s. Paid close attention to the instructions and it worked great.

Hey, great video. Been there, done that and bought the tool. Rather than trusting epoxy I tapped ever so carefully with a fine thread and inserted plugs made from set screws. I used lock-tight on them of course. I also used a large piece of aluminum as a heat sink between the intake and carb. Several hours with a hole saw and files. That was thirty years ago, not my car but the guy I did it for was a collector. I presume it’s still alive.

I love them and set them up to have a millisecond of hesitation when I jump on it I like that kick in the ass wtf just happened feeling and the look on the passengers face is priceless lol one thing you didn't cover was the fact that they will run about anything from a 262 to a 454 w out a lot of major changes the secondaries only give it what the motor calls for edelbrocks have that counterweight to accomplish the same idea but I always thought the quadrajet was as you said all around better the engineers put a lot of thought into them hell I have one I took off of a 78 trans am 400 motor that had been in someone's shed since 1999 and I bolted it right on a 305 and it's fine runs great kick in the ass secondaries etc etc i think my saving grace was the ethanol like you said in another video otherwise that carb would have been full of varnish it wasnt hit it with a can of carb cleaner and the chevy motor ate a few cobwebs and shes been running great for 6 months

mid to late 90s, we called 'em Rochester's quadra-junk, when it came to cars that didn't need smog. Only used them in the cars that had the requirement to be smogged. Holley 750 dual feed with vacuum secondaries with a good intake was a good replacement. Carter AFB was good to tame a wild engine.

@kevinsartin6059

5 жыл бұрын

I thought the "double pumpers" were mechanical secondarys only?

@tallpaul9475

5 жыл бұрын

@@kevinsartin6059 I meant dual feed, not double pumper, that would be over kill for our use, please forgive me.

I used a quadrajet once and then switched to a thermoquad and never looked back at the quadrajunk. Like you said they fall off in the upper rpm ranges, I had one on a police 318 once and did back to back comparisons with a thermoquad and the thermoquad would very noticeably pull away on the top end. Also because the GM carb throttle plates open in the same direction high mileage engines the 7 and 8 cylinders will be the first to start burning oil and fouling plugs, thermoquads open like every other 4 barrel which gives you a better mix and distribution just below the carb in the intake plenum. Yes the q-junk works decent for an average daily driver but personally I will stick with the thermobog, lol. I have a 1979 d-100 with 3.23 geared 8 3/4 that I built a 383 for 16 years ago, .070 over with 1978 stock 440 pistons for an actual compression of 9.8 to 1, I ported the 452 heads myself and used hughes engines 224-230 @ .050 and .504/.515 camshaft, stock rockers, eddy rpm intake 1 3/4 primary headers, full 3 inch dual exhaust and a thermoquad from a 440 that I tuned the crap out of and that thing would fly, it would push that truck to 150+ mph, whooped a Ford lightning with the supercharged 5.4 once also, he gave me the best race I ever had with that truck tho, in my drivers side mirror I could see him clinging onto my rear bumper at 90 mph.

awesome carburetor video once again. P.S the choke fast idle was probably active in the last part of your video if you were having a throttle plate closure issue. sometimes when you turn them over the secondary cold stop lever will hang, I use quadrajets on all my GM cars. there's a larger stainless heat sink for the underside of these available for racing applications to remedy the boiling problem.

I remember trying to fix the bog on my 84 Pontiac and getting so pissed off with it I was trying to find a used square bore intake so I could use our plentiful AVS supply. I know now it probably would have taken 30 seconds to fix. Hell of a noise it made with the air cleaner lid flipped, I loved it lol.

@will7its

3 жыл бұрын

Best sound ever....

I love this channel. Tony has a wealth of knowledge and he conveys it so it's easy to understand! Thanks Uncle Tony.

Spot on as usual! Ive been Building Q-jets for decades. Ive experimented with various ways to increase fuel flow into the float bowl, and increasing bowl capacity. Still, you are EXACTLY correct. On a hard hitter, it's a challenge to get enough fuel through it to supply engine needs. On a 4×4 truck or whatever, can't beat them. Very stable in nearly upside down operation. Lol. My rule has generally been (in the past) q-jet for mild performance and gentle off roading, Holley for real performance, and eldelbrock for long range target practice on the shooting range. I'm aware of many new carburetors on the market these days, but haven't got to play with any. Regardless, good video!!thanks UTG!!!

@joebradley1520

5 жыл бұрын

Russell Mooneyham you are aware that the years after the qjs toney is talking about have larger bowels right?

@russellmooneyham3334

5 жыл бұрын

@@joebradley1520 as I get older, my "bowels" tend to get smaller. (Or so it seems). That being said, the QJ float bowl that I'm used messing with are the models up to 1985 or 1986. Before the ridiculous electronic controlled primary jets. They still don't have enough capacity for a "heavy hitter". I'm talking about a serious guzzler. Currently building a 454 mild for my square body short step. It will sport one of my modified QJ's. But I'm sure it won't be able to keep up with "WOT" for an extended period. We shall see if it can deliver adequate fuel for 15 seconds or so in a standing start quarter mile run. At 5,300 feet of elevation. Looking forward to finding out!!!

@joebradley1520

5 жыл бұрын

Russell Mooneyham electric fuel pump, problem solved

@russellmooneyham3334

5 жыл бұрын

@@joebradley1520. Not always. It occurred to me while I was finally getting to eat my supper, that you might be under a false assumption. Hopefully this is not the case. As far as I know, the "Rochester Quadrajet" (the carberator on UTG's right), never appeared on Chrysler vehicles. (I may be wrong about this, but I'm pretty sure it was exclusive to GM vehicles), and I'm almost certain that the "Carter Thermoquad" (the one on UTG's left) never appeared on factory GM vehicles. As far as "electric fuel pump problem solved" response, I will disagree. The problem is the fuel inlet capacity. There is just not enough fuel flow opening to keep up with a ",heavy hitter". No matter how much you supply, you can only get so much through the needle and seat assembly on a Rochester Quadrajet. This is one of the places that Ive been working on modifications..... Also, there's a slight chance that I'm wrong about factory placement of these two different carburetors. Unlike many on KZread, I don't profess to know everything. Lol.

Just checking in to make sure Uncle Tony doesn't have a cigarette in his hand. Keep going!!! We're all proud of you and rooting for you!!

Great episode very insightful I was always raised to believe the “quadrapukes” were over complicated junk carbs but I’ve always heard that they make good street carbs in you know how to mess with them

Had a Q-jet on my 1967 Galaxie 500 390 car and 1971 Torino Cobra both of them ran and drove awesome with great performance

Tony a tip for you and and anyone else watching your this video the phenolic floats that came in these carbs are really bad about soaking up fuel and making them heavy causing a flooding condition.. Always weigh the float to see if its within speck or go ahead and replace if you have the carb apart.. Float adjustment is critical to this carb also.. Thanks for the video!

I've used quadrajets on my chevelle and my dad's c10, not by choice, but because it's all I had in a 4 barrel. They run smooth and efficient when rebuilt and tuned correctly, like you said. I will say, I once bolted a 780 cfm Holley on my chevelle's 350, and it's demeanor changed from when it had the quadrajet. With the Holley it just felt more aggressive and even roared differently. It was temporary, didn't even get to drive it, but I noticed the difference. Great video

Hi, Tony I worked in a general repair garage in the 1970s and you did a great job in describing the problem with he Q jet I have rebuilt many , a problem that you did not mention was when they went to the composite float that would go bad and sink and cause a flooding condition.

@allanbrogdon3078

2 жыл бұрын

Dad taught me to scratch the float with a thumbnail and look for fuel seeping from the scratch.

I just watched your video on the 2bbl, and asked you to do one on a 4bbl. We're part way there. Let's take them apart! I think the carb is the least understood part of an older car. That and auto trannys. Thank you Uncle Tony.

Thanks for the video and insight on the QJ. I had that issue with the fuel bowl emptying when it sat for long periods. Had it rebuilt and the problem addressed. I had tried a Holley spread bore a while back but didn't like the flat spot around 3 grand that I couldn't get rid of. I also use a non-conductive spacer under it to control heat dispersion.

Driving around town they give better fuel mileage than a 2 barrel. The primaries are rather small, but the punch is there when you need it. Worth a mention the little spring on the secondary air doors sometimes needs adjustment and that's often the reason they get that bog going on.

I used to make QJs run circles around a Holley..Put a Ram Air float in. Increase the bowl capacity. I miss these carbs.Used to tune the primaries by swapping metering rods and hangers..pen drilling the secondary fuel feeds, swapping rod hangers. Nothing beats the sound of those coffee cup sized secondaries opening up. Most folks were stymied by the Air Valve adjustment. Tony, I had a catalog that listed every metering rod / hanger combo with part numbers. The epoxy trick was mandatory on the bowl.

Dad had a quadrajet on his factory 350/300 70 Impala. He said he went out at lunch on a cold start and the engine spit back through the carb. Try as he might rebuilding the Quadrajet, he never could get it to idle right again. He even changed the cam since it had 80,000 miles and was getting wear. But the idle never would come back to proper adjustment. He finally just parked the car. So here I sit with it... I was never brave enough to tackle it. For one I know I'm not near as experienced as Dad. So what was the use. But you have shed light on possible causes. Thanks for a good informative video AGAIN, as always...

So uncle Tony has just taught me why it is that I really love the Quadra jet over any other street/strip carb I've ever run! My hometown track in Odena Alabama is only an 1/8 mile Track!! Haha I've been arguing about that with ppl for yrs over Q-jets. But it was my experience..... Some mite say lack of, but there was real experience in the eq

I love the q jet,such a good adjustable carb, the cam for secondary metering rods wears out,the primary throttle shaft usually needs to have bushings installed or it won't return to base idle, well plugs leak, can be sealed.sometimes you can't richen the idle enough to get rid of a lean idle bump you can usually fix that with a tip cleaner used to clean a torch,but they give good performance.id go with the electric choke.

I have one on my 67 Cadillac Deville . I'm 57 and have built and tuned these carbs for yrs . I do have the heat soak issue with modern gas . Its more problematic at ambient temps over 85 . I use 180 octane booster and lead additives . It burns a clean tailpipe . I enjoy the videos thanks !

The Rochester has an adjustable part throttle screw - the APT - that's very good at tailoring transitory response and easy to access

@NCOGNTO

5 жыл бұрын

@1967 Chevelle LM7 well I always thought thermoquads were "smog era" carbs kind of late to the party . The 60's carbs were more performance oriented . A 67 GTO or Cadillac Qjet will work good on most hotrods , but it's harder for 70's carbs because of smog restrictions they didn't have "performance" versions . The Tquad was one of the last carbs made before FI started

the BEST video on the Q-Jet I ever did see

I have a quadrajet on in my 71 gmc with a 307. It is great for daily driving. Starts easy, idles great and only bogs alittle when you stomp on it.

Tony, love this old tech thing! I graduated HS in’88. Not a mechanic. Just loved cars messing around. Still love ‘em. Good info to get up to date with old tech! Thanks!

love the Rochester, for a simple street fighter application nothing is more reliable and trouble free. it all comes down to purity of purpose.

Finally a little love for the Qjet. For what they are it’s a great carb for a daily driver and street light racing. You have the economy of a tinny 2 barrel carb and when you step on the loud pedal and those toilet bowls start to open away you go.

Love Quadrajets. Always have, always will. First carb I ever rebuilt (or tried), as an 8 year old kid.

The Quadrajet is what is on my ‘69 Buick Electra 225’s 430 V-8 Engine. Bought completely rebuilt and refurbished spare that I had intstalled and then had the Original rebuilt and refurbished and now is my back on the garage shelf. The are VERY smooth operators!

Had a 63 BelAir back in the 90s , 350 , Powerglide and a Quaddy . When those secondaries opened up it was like kicking it down a gear and taking off , good times 👍 cheers Uncle Tony from Aussie , love your channel 😉

I had no issues with my quadrajet at all,never had over spillage due to heat,but I was running an aluminum intake edelbrock plus a one inch spacer on my semi street sbc 350,love the Rochester

Your absolutely correct. There is a few tricks to make them alot better are ways to pump them up.

This is great i usually ask my dad about stuff like this because he was a mechanic for 40 years but he gets rather annoyed

I was wondering when you was going to make a video on quadrajets.

@coronapack

3 жыл бұрын

Where you "were". Not "was". That drives me nuts.

@datraktorman69

3 жыл бұрын

@@coronapack well it'll have to keep driving you nuts.

I love the Q-jets. The current one on my 72 had a "rebuilt" tag on it from some big performance shop. Never ran right. When i tore into it, the piston for the primary rods had the pin on bottom nipped off with side cutters or something. It had no APT adjustment because of this and the rods would pull all the way down into the jets under vacuum. Also, when tuning. the secondaries should only open under load. if they open when you blip the throttle parked in the driveway, the spring is too loose. I've had 7 quadrajets on cars over the years, including 2 of the electronic ones. I've had a ton of accelerator pump problems, worn butterfly shafts, bad choke pull offs, stuck needles and bad floats, and just general crud and varnish issues, but i don't think i have ever had one leak fuel from the bottom plugs.

The Quadrajet is a bit more difficult to rebuild than a AFB but I found it to be a GREAT carb over the AFB on my 1976 3/4 ton chevy truck

Love it! Always learning! I myself love thermoquads but everyone hates them!

Awesome Tony! Thanks! Do one on a Holley next. I got a 2 barrel Holley on my 78 International Scout I need to rebuild.

@MrTheHillfolk

5 жыл бұрын

Some of those are funny lookin, looks like a 4 barrel holley they forgot to cast the secondaries on to. Most of em ive seen ran well though.

Quadrajets are the best "all around" carburetor. They do everything well, but nothing really great. Depending on what you want, they get good mileage for a cruiser, they perform well for mild street racing, and they work well for towing. They perform as well as (if not better than) throttle body injection and almost as well as port injection. I use them on all of my old trucks.

For the Q-jet, use thick fiber gasket (to insulate). Use a external air duct to feed the carb.(olds bumper ducts). Also use a cool can packed with ice. If you use a electric fuel pump, use a DODGE fuel filter (3 tits) that has a small return to the tank, so the fuel line does not heat soak. One last trick, use a second bumper air duct to feed cooling 😎 air around the outside of the carb. Datsun used cooling air to the injectors on the 280 Z. Because the injectors would get so hot 🔥 and fail.

I had a buddy that drag raced with a quadrajoke carberator back in the late 70's. We all made fun of him wrapping a bag of ice around his carb, but in all fairness, he ran a pretty tight quartermile.

I rebuilt a few of these and have one on my Mazda B 2200 with a small block chevy. Works great! The other benefit is I can usually get these things for free and for the price of a kit I've got a new carburetor! ;) BTW, these videos are fantastic and we are of the same era so there is a "memory lane" vibe ever time I watch one. Thanks uncle Tony!

Horses for courses. There is no one end all do all. Have to define what you want then build for that. I love me a Big Qjet on street stuff that gets hit hard every once in a while. Or a thermoquad. Or an AFB. Once you accept the limitations and work within them life is good.

Love the Qjet! Work the bugs out of it and you will have the best street carb made.

Tony's a living car encyclopedia.

My 1st mild built 350 had a 2 brl Rochester,all I wanted was a 4 barrel and after I got the intake I went through every 4brl carb I got my hands on. But I was young still new to the "hotrodding/dogging of vehicles" and didn't know how to adjust or build anything but the old 2brl Rochester. So when I started looking for a 4brl the ones I got a hold of were already old and needing rebuilt. None done right so I put a plate on the intake and used my 2brl until one day a new "insurance"job got dumped in mines down from my house. (People always dumped stolen cars in the old mines) Somebody carried a Monte Carlo SS and set it on fire but it just burned the inside,it had a Quadrajet and I put it on my truck and it was great. Nothing sounds better than a Quadrajet when it opens up at WOT. I'd still run them on what I drive today but have always been scared to try and rebuild one so when I need a carb now I buy a new or reman Edelbrock.

Dude this vid has me watching you now, you gave a history and knowledge lesson that was well needed, spot on nail on the head about quadrajets

The professor has spoken needs no introduction he is the one and only Uncle Tony great video have a good night my friend take care

I'm in full agreement about the overall smoothness of the Quadrajet. For a carburetor it's action is very seamless. My shop teacher fabricated a dual spreadbore manifold that allowed for two Q-jets on his 396. his reasoning was that he wanted the increased fuel delivery of a dual quad set-up, but he wanted the gentle transitioning offered by these carbs. He definitely passed on the love to me, i just smile when i hear someone utter the phrase "Quadrajunk" while having to re-adjust their street avenger for the third time... Great video Uncle T! Also, we're those resin bodies on the Thermoquads ever prone to becoming brittle over time? Seems like I remember hearing of that at some point... Hrmm...

@UncleTonysGarage

5 жыл бұрын

They don't really become brittle, but there are wells at the bottom that tend to separate over time

Tony I love your videos about the carburetors really helps after years of not doing my mechanics in the backyard like I said I'm getting back into it again and it's like riding a bike but I'm relearning and yeah I'm learning about the cast iron intake that's on my engine it's got the heat risers for the to warm the carburetor up for the choke and I was told just to plug them so I plug them and doesn't get blown gasket out underneath the Edelbrock carburetor in the spacer plate now I'm fixing to get it so I can actually get some idle mixture out of it and get them and get that title all the way down to where it's supposed to be six or eight hundred RPMs I love you videos with carburetors do more if you can please

I’m mostly a fuel injection guy (I design the computers that run them as a day job) but the Quadrajet is my favourite carburetor and use them on non-emissions engines. It may not do as well in accuracy as a good EFI system - that mostly is for emissions - but the drivability and especially part throttle tip-in and transition into the main circuits on the Q-jet is very smooth. You have to understand them to tune them but it’s not really that hard. The front half is pretty simple, the back half is kind of like an SU carb.

As a chevy guy I have some experience with these. I know how they work and some of the qerks like the low fuel pressure and inability to use large needle and seats without certain float combos or especially low fuel pressure. Generally a conservatively sized holley is more straightforward to tune and give better throttle response. But I've seen some qjets run good. I had one with some lean metering rods that shouldn't have worked but the engine liked it. I had a cheap parts store aircleaner with a paper filter that was maybe 2" tall maybe 1-1/2" and I had a stock fuel pump. I tried all the normal stuff to make the car more speedy. Taller cotton gauze air cleaner, allegedly better fuel pump, thinner metering rods, shims in the rod hanger, bigger exhaust. Despite the plugs looking fine the car only went slower with new parts. For whatever reason the car liked the lean rods and low filter lid which is counter to every Dyno test I've seen on airfilters other than it not being a dropped base filter which is generally actually a good thing even if the filter isn't too tall. I don't know if high base low airfilters typically work well on qjets but I'd try it again.

Great video Tony! Maybe in the future you could do a longer video or series of videos explaining to the younger generation on how to diagnose problems with them, how to fix them & what's involved in tweaking them for optimal performance. I love the Q-jet but as you said it is not the best 4 bbl for serious drag racing use because of the one central fuel bowl, but if you run a 3/8th" fuel line like you said & a phenolic carb spacer & block off the heat riser ports either with thin metal (my friends & I used to cut up soda cans) or special intake manifold gaskets alot of the heat soak issues will be minimized. I ran a 850 cfm Q- jet on a 550 horse Pontiac 455 & ran the special carb spacer & intake gaskets & hardly ever had heat soak issues, but Pontiac engines also have an advantage alot of other engines don't in the fact that Pontiac specifically designed their intake manifold so that large quantities of air can get under the manifold to cool the intake charge dramatically as compared to other designs. It was one of the first if not the first "Air-Gap intakes"!

@UncleTonysGarage

5 жыл бұрын

BB Chrysler has the same basic design intake

Great and true review UTG. Many Ford SCJ, GM BB performance cars, and of course Chrysler cars came with great running Q jets. I love them and when right, better than anything for gas mileage and performance. If heat/vapor lock is an issue, I use a Phenolic (wood) spacer that makes all the difference!

I ran Holleys and Carters on my Mopars but i do remember The Holley spread bore carb and came close to installing one. I always loved the principle of small primaries and 55 gallon barrel size secondaries.

Love the Q-jet but with the dozen I have owned all the float bowls leak,but I drill and tap the well plugs with a 6-32 machine screw and coat the screw with epoxy when installing.

Using a long pump shot like the caddy one is crucial. Holley has a spreadbore too you know. Quadrajet for the street can’t be beat. A good shielded phenolic gasket solves the heat issue that all carbs have. Well that and a return fuel system that is set up for high volume instead of high pressure.

Both the Quadrajet and 6xxx series Thermoquad are excellent carbs, and not difficult to set up properly. I’ve gone deep 11s with both in fairly mild street cars.

Hi the Quadrajet 2 & 4 barrel carbs were used on all GM cars and trucks, the heat soak problem goes way back when they ran exhaust thru the intake manifold to run the automatic choke on V8's

I like them to, easy to repair and good over all performance.