Rochester Quadrajet Carburetors

[larrys2011]

I have seen several postings on what junk these carburetors are and I would like to address one of the reasons that stood out in a couple of way old posts.
#1 complaint was stumble when secondaries came in.
TWO items control secondary function.
ONE is a vacuum dashpot front left of carburetor and when you floor it and vacuum drops it lets the large upper secondaries you can see gently open. If they open too fast you get too much and it will stumble. THESE upper secondaries have an allen head lock screw and TWO is a screw to set spring tension and some manuals show actual windup of spring. Otherwise turn 1/8 of a turn until it comes in smoothly. I love my 5.7 with Quadrajet and it is good on fuel by design of the carb and will do 51 MPH. Quads can be enhances for more performance with jetting etc. SO WHEN YOU COMPLAIN ABOUT STUMBLE AND STATE YOU HAVE REBUILT IT TWO TIMES. You have not done your job correctly. Primary jet well leaks are another deal but many kits have devices to help the plugs stay seated. If you have questions feel free to contact me. I have lots of hours with Quadrajets and making them function very well.

 

[jimmbo]

The Q-jet is probably the best engineered 4 bbl carb of all time. 99% of the carbs 'problems' are users/mechanics/bench-racers who have no real clue as to how it was designed to operate and have no desire to learn.

 

[fhhuber]

The main problem with Quadrajets is people who don't know how to fine tune them.

I used to tinker with my Quadrajets on a car (yes... 2 on one car) and worked to get the best responsiveness AND good fuel mileage.

One of the simplest tricks is adjusting the spring to delay opening the secondaries. Most people end up with the secondaries opening early and the accelerator pump injecting too much fuel causing a hesitation after you increase throttle.

 

[boatman37]

i loved the Q-jets. i have rebuilt plenty and ran them in my racing days, although jet changes and metering rod changes were a real pain. the biggest issues were the well plugs leaking (JB Weld fix there) and the throttle shaft wearing out and leaking but they have a fix for that too.