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 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.
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.
first tutorial ever take it easy on me. i didnt have the luxury of a vacuum
gauge around so i did a general way of tuning a carb by ear. If u want a
more perfect tune i suggest you use a vacuum gauge and or take it to a
Rochester Quadrajet, the results!
Two mishaps, the first shown here, the choke coil I got was wound
backwards, it made the choke butterfly wind up TIGHTER as the engine warmed
up. I swapped on the one from the old carburetor fast enough, the second
mishap made me feel like a crud and what did I mess up later that evening.
The car would not start leaving the Etobicoke -Queensway show. It was not
getting gas. We got it running by priming the carburetor, and boy, was I
ticked at myself. In the end it was not my fault it looks like. The new
accelerator pump umbrella and rod was a very poor and frail design, the
umbrella came detached and stayed at the bottom of the of the pump well,
and was a distressed mess. The maker will get a note from me. The upshot?
The old assembly went in, all is perfectly fine, the slight tip-in
hesitation is gone now too. Stupid lack of pride it seems these days
making parts for even simple things like an old carburetor.
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!
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)
Replacing an HEI Coil & Quadrajet Comments (Not a "How-to")
The '77 Olds 350 suddenly developed a pretty nasty miss under load, which
slowly worsened to a miss at idle too. If you got close to the distributor
with the engine running, you could hear the coil arcing all over the place!
The Delta is equipped with the usual GM HEI distributor.
'77 Chevy K20: Quadrajet Choke Pull Off and Fast Idle Cam Observations
1977 Chevy K20. 350 crate engine. Rochester Quadrajet 4MV carburetor with
Truck suffers from unexplained hesitation and bogging when in forward
gears. Tends to rev just fine after a few minutes of mixed idling and high
revving. Checking choke operations as well as a possible sticky fast idle
cam as part of the process of elimination.
- Truck is allowed to idle/warm up until 2:25 mark, at which point the
engine is revved to about 2,000 rpm, and can be heard bogging (a hissing
sound can be heard). The fast idle cam is seen dropping. Fuel flow can be
seen in the glass-cased fuel filter right before the carb as remaining
- The engine is revved again about three more time up until 3:00 minute
mark. The engine revs slightly higher, but the hissing and bogging can
still be heard.
- Engine is revved again at the 3:35 mark, slightly past the 3,000 rpm
mark. Hesitation and hissing still evident, but less so than before.
- Engine revved at the 4:25 mark to about 4,000 rpm. No hesitation or
- Transmission is slowly shift through every gear starting at 4:55 mark.
Shifted back into Park at 5:05 mark.
- Engine revved again at 5:10 and 5:17 marks to 4,000 rpm. No hesitation or
hissing is heard.
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