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
How to identify 4 barrel carburetors
Here's a guide to help identify the most common 4bbl carbs including
Edelbrock, Quadrajet, Holley and Thermoquad.
There are a few older or more obsolete carbs not shown including Rochester
4G, Autolite-Motorcraft 4100/4300/4350 and Carter WCFB that I'll detail in
the future provided I can actually find one.
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.
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
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.
Rochester Quadrajet Marine Carburetor Rebuild Part 2 of 3
http://www.carburetor-parts.com is happy to provide this informational
video about rebuilding the Quadrajet marine carburetor. You can buy marine
More Quadrajet tuning, some things! Part one in this saga on Sept 13, 2010
The car has a slight stumble and surge at a light throttle cruise at about
55 to 60 MPH. By swapping out the .050 metering rods to .048 units, the
stumble and driveability concerns are now gone. Going richer would mean
worse fuel mileage one may think? No! Now that the mixture is right, LESS
throttle opening is needed now, which means higher vacuum, and this way the
metering rods will block off the correct amount of fuel, and in the proper
timing and percentages, so the car runs much smoother. As stated many
times, patience and reading up on, and understanding how these intricate
carburetors work will help out very much! Enjoy!
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.
here is a technique for re-bushing the throttle shaft without drilling.