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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!


 


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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.





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





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 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.





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.





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.





re-jet your Quadrajet (part 2)
rejetting a Quadrajet





Everything you wanted to know about automatic chokes but were afraid to ask pt2
I've noticed many people drive vehicles with inoperative chokes. Even though chokes can be intimidating, repairing and adjusting them actually is very simple. So, stop pumping that accelerator and follow along as we look at how chokes work and how to repair them.





for Tim - Rochester tips





How to rebuild a Rochester Quadrajet part 2
Continuing the disassembly process.





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





750 vs. 800cfm Rochester Quadrajets-how to tell them apart
There exists a ton of misinformation regarding the actual airflow capacity of the Rochester Quadrajet. Not many people know how many variations there are or how to tell them apart. Here is a simple video explaining how to identify each size based on casting design. I will cover the "cfm-limited" carbs in a separate video.





New quadrajet set up
New air-gap manifold and custom/rebuilt q-jet. Sounds good but I still need to set the timing on the distributor and the carb is tuned already. Hope you like, nothing to fancy just a few revs and walk around...the Exhaust is true dual no x/h pipe and it has cherry bomb glasspacks(3 inch)





How to measure and adjust Quadrajet float level
I have had several requests for this, so here you go: 1. The airhorn has to be removed to do this, but the carburetor does not have to be removed from the engine. 2. Some data says to measure from the toe(end that is opposite from the hinge), some say 5/16 inward from the end, etc. I suggest following the specs for your particular carburetor. 3. With the float in the raised position and the inlet needle lightly seated, measure from the top of the float to the top edge of the carburetor with NO gasket in place. If you have to adjust the float, bend at the area that has the cutouts, 4, If you are experiencing flooding issues then it is an excellent time to install a new needle/seat and float and that should cure flooding problems that are not choke-related.





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