How to Rebuild a Carburetor: Quadrajet 4 Barrel - Muscle Car S4, E18

Learn everything you need to know about Quadrajet carburetors, including how to rebuild one correctly, what kind of performance to expect, and why they've gotten a bad rap. Plus, we'll show you how to apply do-it-yourself floor coating.

PARTS USED IN THIS EPISODE:

Edelbrock: Edelbrock Q-Jet Series Carburetor Calibration Kits.

Loctite: Threadlocking compounds.

UCoat It America LLC: UCoat It floor coating systems are designed for the do-it-yourself-er. Every UCoat It Kit comes complete with applicator tools, instructional video, applicator guide, and all the coating materials necessary for application.

O'Reilly Auto Parts: Choke Thermostat

O'Reilly Auto Parts: Carb. Rebuild Kit, Float

O'Reilly Auto Parts: Choke Pull Off, Float, Filter

O'Reilly Auto Parts: Carb. Cleaner 5 Gallon

O'Reilly Auto Parts: Miscellaneous

O'Reilly Auto Parts: Case of Brake Clean

O'Reilly Auto Parts: Touch Up Paint, Primer, MetalCast

O'Reilly Auto Parts: Spray Gun Brush Kit

The Eastwood Company: CARB. RE-COAT GOLD AND SILVER 2 EACH, CARB PREP (6)

WD-40: Multi-Purpose Penetrant and Lubricants.

[streetwise-]

Back in the 70's when I was in my 20's I bet I rebuilt 30+ Q-jets when I was a mechanic working on boats with GM motors and friends muscle cars. Watching your video I was surprised how much I forgot over the years. Good video, thanks for the memories.

[robertwest]

The Quadrajet is the closest you will come to fuel injection results without actually going to fuel injection. You can control and tune every aspect and range you need with these carburetors.

One thing I am surprised they never addressed was the throttle shaft wear. The base plates should have had bronze bushings installed from the factory.

[robertemmons]

Its been a long time since I had rebuilt a Q-Jet. When I use to run them back in the 80's and early 90's I had nothing but great results using them on my '70 Nova, '77 El Camino, '67 Catalina, and '82 Trans-Am.

[gvi]

Low budget project from this channel? That's rare

[billiebobthemechanic]

Q-jets are great carbs! I would grab every one off the big block caddy’s in the junk yard and build them for my small blocks. If you kept your foot out of it they would get great mileage but when you stomp on them they made the best throaty sound when the toilet bowl secondaries opened up. And I was familiar with all the tricks they talked about in the video.

[johneason]

In the 70s I had hundreds of the Qjets apart. When built right they worked fantastic. I had a custom one off that I built for my LT1 never had anything else on the engine!

[petersd]

Quadrajets rule, best carburetor ever conceived, once properly tuned delivers glorious acceleration

[haydenc]

Brown recluse spider ya got right there...
Nice rebuild..thanks

[westogarage]

ripped the TBI fuel injection off my truck for one of these. ABSOLUTELY LOVE THEM!!! i’m convinced these are the best damn carburetors out there!

[nbowlingtrio]

I always hang my carbs upside down to check float level when they're in that position installed. It is a very important part as you said.

[larryhutchens]

Been building Q-jets for a while & You guys did a fair job but missed a few critical items. First off the Q-jet is a fairly complex carb w/real good metering aspects, the small primary bores will give your engine good throttle response at low speeds. After using one a square bore will feel mushy at low speed by comparison. Spread bore unlike any other? What about the Carter thermo quad? To remove the screws holding the throttle butterflies in place better grind off the part of the screw that extends beyond the throttle shaft or you will likely break the head off the screw & will have hell removing what's left of the screw. The end of the screw is staked at the factory to prevent them from backing out. I use a Dremel grinder w/ a small carbide burr to do the job. Screws for the bottom plug, 7/16" NF tap will work better. I have a length of 7/16" aluminum rod threaded to use for plugs. Base needs to be resurfaced on a large belt sander, they can be really warped. Same w/ the main body. The most common mistake owners make when they have a problem is to over torque the hold down bolts & warp everything. Easy way to check the main body for warpage is to look at the slots where the secondary divider plate goes. If they are wider at the top than the bottom then the main body is warped. I have a way of straightening this part but it is difficult & the process is too lengthy for discussion here. You neglected to cover the installation of the choke lever onto the choke shaft, a very frustrating process. On the chevy carbs the plug at the back of the fuel inlet is also prone to leak. Most times this can be corrected by driving the plug in tighter (it is a tapered plug) & re-peening the area around the plug. Lot of critical adjustments to make also, especially the choke pull off which controls the rate of opening for the secondary air valves. If not done properly the carb will bog at WOT or the secondary air valves will open too slow causing disappointing performance. You guys did a fair job otherwise.

[dannieves]

Epoxy is fine for sealing the soft plugs over kill to drill & tap them. 25 year ago i rebuild the computer controlled version of this caburator then set and adjusted them for AZ state emissions.

[jameswalton]

Done several of these over the years.
Brings back memorys.

[Thelongmanable]

*_There is something satisfying about watching them rebuild something completely reached out..._*

[andhag]

Whoa, I just took a quadrajet appart for a rebuild! Nice timing!

[christophersallee]

years ago the Holley on my 73 mustang mysteriously got damaged during the engine rebuild. my friend offered me a quardrajet cheeper than replacing the Holley. I was young and broke so I went with it. he installed it and tuned it.... it was a massive upgrade on that little 351w compared to the factory Holley.

[arthurgay]

Something I only recently found out is that when mercruiser marine first started using Chevy engines in the mid 80s they had their own version of a q- jet. It looks the same but it's already been modified for performance with bigger jets and passages. Marine application means no restrictions for emissions or power. They are also made up of a different kind of aluminum alloy that will not oxidize at all. My boat has a 307 out of a 73 Chevelle. I put the cam and lifters and the heads from a 300 horsepower 350 mercruiser that was sunken in salt water for a week. Then brought out of the water and sat on the shore for 5 years without being drained. The block was destroyed by freezing but the carburetor survived except for the little springs inside. That tiny little spring on the low speed metering rods was completely dissolved from the salt water and being left for 5 years. The inside of the carb just needed a can of brake clean with a straw and it looked like new. The exterior is already covered in black powder coat from the factory. All mercruiser carburetors have an aluminum tag with a part number to make it easier to get the right kit. Mine is from a 1985 four winns 25 foot cuddy. I had to scrap an old carb just for the tiny springs and I had to drill out the port and install a tube for the vacuum advance . Marine carburetors don't have any vacuum ports at all. If you need to hook up a brake booster you will also need to either drill and tap the port for the vacuum or even use a throttle plate from another carburetor that is the same. Just the fact that there is absolutely no corrosion anywhere inside or outside just blew my mind. It spent a week sunk at the dock and then 5 years on shore without being drained... Try that with an automotive carb !!!

[mindeloman]

I had an old ponitac that was in dry storage for 12 years - put up on jack stands. 400 engine with Q-jet and a 400 trans. Gas tank was emptied and the radiator/engine block drained. After 12 years i rolled it out into the sunlight, topped off fluids, and installed a battery. I primed the fuel bowl with gas, turbed the key and guess what I had to file the points. After filing and the points the engine fired and ran on choke like it was just parked yesterday. When it got warm i bumped the throttle and it came down to idle. I drove it to the gas station to top-off the tank. That was 5 years ago and it still runs great. Even the accelerator pump works fine. I haven't made a single adjustment on the carburetor. I never understood the hate surrounding Q-jets. They are a great carb if you know how to work on them.

[Friedbrain]

Actually they went to 850 cfm and i love Quadrajets. Used to make a bushing for the center also...worked wonders for tuning. You didn't need to put threaded plugs in it though. File down and then epoxy over the stock plugs and it good to go. Vinyl interior wasn't exactly "luxury" LOL and neither was the abhorrently bad fuel mileage

[nFlames]

If one uses a 72 jet & a 49 primary metering rod with a lite power piston spring over 20 miles a gallon can be had in the 396 & 402s. The 350 would get 24mph sometimes better with that set up. One would also have to tune the dist advance curve.
Setting the secondaries for power one could enjoy both worlds mpgs & tons of power.
The secondaries would take some drilling on some of the orifices & grinding on the metering rods.
The Q jets were fun to work on to get max MPGs & Max Power.
There was no other carbs that I built that could do the same.