Quadrajet question
Thread Starter
Racer
Joined: Apr 2006
Posts: 340
Likes: 0
From: Warrensburg MO
Quadrajet question
I am rebuilding the quadrajet on my 77 Corvette. Automatic with air, carb #17057204. I have the top off the carb. There is a well where the power piston resides, and next to this well is another, with an adjustment screw, that is supposedly set at the factory. I don't know what it does. The manual says not to mess with it, unless you believe it has been tampered with. I don't believe the carb has been apart before, but I could be wrong. Any advice or experience with this adjustment? Should I just leave it alone? Thanks
Tommy
Tommy
Le Mans Master
Joined: Mar 2004
Posts: 7,493
Likes: 1,502
From: Little Rock AR
Adjustable part throttle screw - leave it alone. 
I didn't know and read about it after I had already dissasembled it. The adjustment takes specialzed equipment to set it right OR a lot of trial and error. It has an effect on part throttle mixture. You can make a tool to adjust it and punch out a hole in the top of the carb and add a threadded plug to make fast changes in an effort to get it back to where it needs to be.
IMHO - if this one ain't broke, don't fix it.
-Mark.
I didn't know and read about it after I had already dissasembled it. The adjustment takes specialzed equipment to set it right OR a lot of trial and error. It has an effect on part throttle mixture. You can make a tool to adjust it and punch out a hole in the top of the carb and add a threadded plug to make fast changes in an effort to get it back to where it needs to be.
IMHO - if this one ain't broke, don't fix it.
-Mark.
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
If you want to remove the APT adjustment screw, screw it down until it lightly seats. Count the number of turns it takes to seat it. This will give you a reference for reinstalling it.
BigBlockk
Later.....
BigBlockk
Later.....
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
When I rebuilt my Q-jet, I used Doug Roe's book on the subject (which is excellent). I remember in it he said do not attempt any adjustment of that screw. I followed his advice and, BTW, my rebuild turned out great, much to my amazement. Good luck. 
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
Thread Starter
Racer
Joined: Apr 2006
Posts: 340
Likes: 0
From: Warrensburg MO
