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.
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 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: Ever since Charter "fixed" my internet and cable after the lightning
strike, it hasn't worked right. Go figure. So, if you see this posted then
I was finally successful in getting a video uploaded.
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 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 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.
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.
The last thing to be looked at on the wagon, but really, no old car project
is ever done, things keep being played with and adjusted. This is a
correct Rochester Quadrajet 4-barrel carburetor I got some time ago, and
has been renewed with new seals. The bushings and other hard parts were in
good repair, so with the new seals. T o note, I called out the first three
serial numbers as being "701" when in fact it starts with "704" . When
building up a Rochester, one has to understand they can't just throw parts
into it, they may be unhappy with the results. They should also be ready
to have to change a jet here, a metering rod there, a spring or two after
the unit is on to get the car running perfectly. The Quadrajet is a sweet
carburetor, once you understand it a bit. As I am doing. It is running
well, but will need a bit more tuning in the way of a stiffer primary
metering rod return spring. Other then that, the car has more bottom and
top end power, mid range is the same, but the bonus is, fuel mileage has
picked up, the leaky bowl of the old unit is gone!
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!
Terminator EFI Install and Overview - Chuck's Garage
Chuck installs Holley's brand new Terminator EFI system on his '70
Chevelle. First we take off the old carburetor and bolt on the new Holley
EFI Terminator throttle body. Then we mount the Terminator EFI ECU and
wiring harness and begin wiring and plugging everything up. From there we
go under the car and tackle the fuel system. After we get everything set up
with the handheld tuner we take the new Terminator EFI system on a test