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How to de-bog your Quadrajet part 2

The Rochester Quadrajet has gotten a bad rap over the years, but it's actually an excellent carburetor once you understand how they work. Often referred to as "Quadrabog" or "Quadrajunk", many of the issues these units suffer stem from neglect, or "modifications" that do more harm than good. Being a spreadbore, air-valve secondary design, the Quadrajet is capable of flowing 750 or 800 cfm of airflow, eliminating the need to buy different carburetors when your set-up changes. In addition, the small primaries make for great drivability and fuel economy. In this clip, I'll discuss theory of operation on the secondary side, since that's where most problems arise. So, leave your preconceived notions at the door and let's see what makes these carburetors tick.


 


More Videos...


How to debog your Quadrajet part 3
In the first two videos we looked at operational theory of the Quadrajet. In this episode we'll explore a couple mistakes the home mechanic often makes in an effort to improve the performance of this unit.





How to de-bog your Quadrajet part 1
Sorry guys, I got the videos a bit out of order. The Rochester Quadrajet has gotten a bad rap over the years, often called a Quadrabog or Quadrajunk. In fact, this is a great multipurpose carbureter once you understand how they work and what not to do to them. In this clip I introduce you to the Quadrajet and begin explaining the theory of operation of these units. Enjoy!





The Infamous Quadrajet Moan
Making a full-throttle pull on the chassis Dyno with our 1972 Pontiac Trans Am with 455 H.O. engine.





how to minimize engine bog with a Quadrajet carb
this is to minimize engine bog when the pedal is to the metal. do not over tighten, very small spring...you want to try 1/4 turns or 1/2...q-jets are good if tuned properly. also when you are tightening screw it will have tension on it so keep the screwdriver firm. 1986 gmc sierra single straightpipe to cherrybomb. you will need a small flathead screwdriver and a 3/32 allen key. be sure not to tighten to much or else your vacuum secondary flaps wont open.





How to diagnose a Quadrajet part 3
Let's take a look inside





Why Quadrajet's are awesome part 1





How to adjust carburetor mixture screws
Here's how to find and adjust the mixture screws on your carburetor. Note that metering-block style carbs such as Holley and Demon more often have one or 2 mixture screws in each metering block depending on the number of venturi. Also those may not be located at the bottom of the carb as in factory carburetors.





re-jet your Quadrajet (part 1)
rejetting a quadrajet





Most relaxing sound for men - Old-School American V8 Corvette C3 1979 (Stingray)
Includes Cold engine idle, warm idle and a bit of revving to about 4500 RPM. I decided to create this video since my Vette now sounds quite loud thanks to the Cherrybomb glasspack Exhaust and removal of the catalyst. The Exhaust is basically stock. I think this is one of the most relaxing sounds for men who are into cars and machines :) Engine: 5.7 L (350 cid) V8 L-48 Transmission: Warner 4-Speed Manual My Corvette is generally in very good condition and it has already been restored once in USA some years before it arrived in our country. I got the car in a state where the exterior + drivetrain were fine, but the interior needed new carpet, some painting and several other components in order to look great. I'm now pretty much done with the interior. The engine used to have issues but those were mostly external (bad thermostat housing, bad spark plug wires etc.). By now the engine is a pleasure to drive, but the Rochester Quadrajet carburetor has hard time keeping the pre-selected idle speed and sometimes wants to hold it higher, then lower. It might be also some extra fuel leaking in from somewhere occasionally. There used to be some vacuum leaks but I've taken care of them. Perhaps I will replace the intake + carb with an Edelbrock setup for next driving season. The engine compression has been measured recently and the results were perfect for all cylinders. NB! We will soon try to film the Vette from another car when driving on a motorway. I'm hoping to get some good footage that way. For more information and work history on my Corvette, Suburban and ex-Jeep Grand Cherokee, please visit my blog at http://www.georgescarblog.com .





Idle Mixture Adjustment on 4 Barrel and 2 Barrel Carburetors
Setting Idle Mixture and Idle Speed on Carburetors with Idle Mixture Screws to Pass the Smog or Emissions Test with a Tachometer





Quadrajet air leak fix and warped air horn repair tutorial.
How to identify a Quadrajet with a warped air horn without diss assembly or running it on a car. These tips would have saved me time and money which is why I made this video. I also discus how to repair a warped air horn and prevent your air horn from warping in the first place. If you have a whistling noise just off idle then you got some work to do. You will never get your engine tuned right, your cold start performing or decent fuel economy unless your four barrel carburetor is just right. Special thanks to Cliff Ruggles for his book Rochester Quadrajet carburetors and to my brother Adrian who spent hours on tuning and fitting. See this video for description of the technique I used to straighten a warped air horn. http://www.youtube.com/watch?v=l_SgQiVf3_0&feature=youtu.be here is a technique for re-bushing the throttle shaft without drilling. http://rmcavoy.freeshell.org/Q_Jet_bushings.html





quadrajet-cam
See 1976 Chevrolet pickup with Rochester quadrajet upgrade on SBC 350 V8. We removed the hood, mounted a camera looking down on the air horn, and took it for a spin, running wide open on an uphill grade. See how the secondary air valve responds to rpm drop at each upshift of the THM. Also included is a smoking burnout.





Identifying Quadrajet vacuum ports
I always see a lot of questions about what various vacuum ports do on a Quadrajet. Here's a general guide that will point you in the right direction. Remember that there were many different Qjets over the years and vacuum port locations and number will vary. This video is representative of 1975-90 carbs. Enjoy!





How to adjust Quadrajet/Dualjet fast idle
Quadrajet/Dualjet Rochesters have a fast idle adjustment screw that is separate from the base idle screw.Here's how to locate it. NOTE THAT THE CHOKE ITSELF MUST BE WORKING IN ORDER FOR THE FAST IDLE TO FUNCTION.





How to rebuild a Rochester Quadrajet part 3
Finishing up the disassembly.





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