Quadrejet Mixture Specs HELP !! :(

[Cw72gmc]

So guys, in a previous thread I told you guys I was having a low idle, low end stutter problem, but ran fine if I was heavy on the throttle. I have a very fair and trustworthey mechanic who has a history with my family look at it. He said he feels it's the original carb, and to the looks of it hasnt been rebuilt in probably 15+ years. We put it back on so I could drive my truck home as I dont have the cash for him to refurb it. I got home and a know it all neighbor was out shoothing the Sh**. I left the truck idling while I ran inside to grab my wallet and garage opener. In that time he took it upon himself to tweek on the 2 front needles Left Fuel Right Air? ? ? Now it's sputtering all over the place, and is even backfiring on accel now around 2500 rpm and off of idle will pop a bit. So not now only was it a fuel issue, but now it's not tunable in a sense that it has issues. What are the stock settings for high altitude SLC UTAH I am in the process of a move, and am needing my truck desperately until my next check when i can have the carb refurbed. Any tips will help greatly!! Thanks!

[webfoot]

Did he mess with the timing too? Thats what it sounds like to me. Those adjustment screws on the front only affect the idle circuit. Assuming you are talking about the 2 screws on the very front of the carb which are the idle air bleeds. Clockwise rotation causes a richer mixture, CCW makes it leaner. General rule of thumb is to seat both screws and adjust out 1.5 turns which should get you ballpark.

[Cw72gmc]

Ok thanks, no he claims he just tweaked on those two. I'm having a lean issue on idle to begin with I dk if there is gunk in the fuel inlet or what, I just think my carb already having delivery issues on the low end combined with the incorrect idle settings are just causing some issues. i'll set it to that when I get of work and see how it does. Thanks so much!

[webfoot]

Cover up the primary circuit with your hand at idle to verify your lean idle suspicion.

This paper is a real good tuning aid:

http://www.corvettefaq.com/c3/QJetTuningPaper.doc

[oldgold70c10]

Turn right to lean, turn left to richen. Turn the mixture screws in until lightly seated, then back off about 2-1/2 turns. Use a good tach for this next part, one that will clearly show small changes in engine speed. With engine at normal operating temp, disconnect and plug vacuum advance at carb, set timing to spec, and
Method 1:
use idle speed screw, set idle to proper idle speed (auto trans in drive, wheels blocked, manual in neutral). Adjust idle mixture screw out to obtain the highest steady idle speed. Adjust one mixture screw in to obtain a 20rpm drop in engine speed, then adjust mixture screw out 1/4 turn. Adjust second mixture screw to obtain 20 rpm drop, then back out 1/4 turn. Reset engine to specified RPM.

Method 2:
use idle speed screw, set idle to proper idle speed plus 30 rpm (auto trans in drive, wheels blocked, manual in neutral). Turn the screws in until lightly seated, then back off 4 turns. Equally turn out both screws until the highest idle rpm is reached. Reset idle rpm to spec plus 30rpm. Turn both screws in equally until proper idle speed is reached (30 rpm drop).

Method 3:
use idle speed screw, set idle to proper idle speed (auto trans in drive, wheels blocked, manual in neutral). With a vacuum gauge, turn both screws out equally until the highest vacuum reading is obtained. Reset idle speed to spec. Turn screws in one at a time until idle speed drops 20-30 rpm, the back out 1/4 turn. Reset idle speed to spec.

I personally like method 3 best, though the other 2 work.
Hope that helps.