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.
Identifying Quadrajet vacuum ports
I always see a lot of questions about what various vacuum ports do on a
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
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 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.
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.
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.
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
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.
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!