The Quadrajet

We take a quick look at the pros and cons of GM's most popular 4bbl carburetor.
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[jdgimpa]

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.

[louisedwards]

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

[edwardpate]

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!

[two_number_nines]

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.

[hilleryclifford]

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.

[christiantomlin]

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.

[alexb.]

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.

[Rick-Williams]

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.

[DayRider]

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!

[johnsaum]

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

[chevelle]

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.

[ShootingMOA]

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

[bertgrau]

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.

[scottsawyer]

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.

[mlhrepairsllc]

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

[paas]

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

[jearly]

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 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.

[parkerbandy]

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.

[historybuff]

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.

[rksg]

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!