Quadrajet question

[carolinafan4life63]

how do you adjust the two idle mixture screws on the front of a quadrajet?? I know that there are two plugs that should be covering the screws ..right??but they are not there ..... telling me that it has been rebuilt or the PO adjusted them. so is there a special tool to adjust these , or what size socket would i use ? i see that the heads on the screws are oval.....also what would be the proper amount to adjust them out after turning them in and seating them???

 

[jms]

Carburetor Adjustment tool, mine was something like $16 at NAPA.
You could make your own (as illustrated in the Roe book), but the flexible handle on the NAPA tool came in handy when working on a running motor. 2 1/2 turns out ought to be a good starting point.

 

[dyeager535]

Doug Roe Quadrajet book is invaluable for learning about these carbs. It's a really good read from cover to cover IMO, and I'm not a fan of carbs, at least anymore.

2.5 turns out from fully seated as stated is a good start, and IME works 99% of the time. May not be perfect, but short of doing it the "right" way, will at least get it to idle more than likely.

IIRC, one of the better methods is to adjust them with a vacuum gauge hooked up, but I can't recall the exact process.

 

[jms]

I did an 'excuse me' lean-drop on mine - motor running at operating temperature; transmission in park, idle speed 650-700, choke open, meter connected to tach on dizzy, close both idle screws in 1/2 turn increments until idle rpm starts to drop, then open both idle screws 1/4 turn, see if idle is stable, if not, open them another 1/4 turn.
IIRC you're supposed to do it with transmission in gear, vacuum gauge on manifold vacuum, and I've forgotten whether vaccum to the dizzy needs to be disconnected. Doing this in a parking lot on a lifted truck with the front bumper in the way and all the emissions on the '85 preventing you from getting the tool on the mixture screw gets really old quickly. But it did fix my rich idle condition...

 

[76zimmer]

I've always adjusted them to the highest idle setting. I don't think it would matter if in Park or not. Just use manifold vacuum.

 

[carolinafan4life63]

cool , thanks for the help guys , much appreciated

 

[wazzabie]

The OEM shop manual calls for adjustments to be made in drive with propane. I'm not sure anyone really followed that.

Is grimreaper still on these forums? I recall him being rather knowledgeable about qjets.