Cliff's Quadrajet Parts and Rebuild Kits

Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: 59bluesilver on September 21, 2016, 05:50:52 PM

Title: Idle Mixture Screws
Post by: 59bluesilver on September 21, 2016, 05:50:52 PM
Something doesn't quite make sense to me. The air mixture screws in this quadrajet shown below are both 1 3/4 turns from the seated position. However, the right one extends much further into the venturi than the left one. Is that the way it supposed to be?
Title: Re: Idle Mixture Screws
Post by: Frank400 on September 21, 2016, 06:28:30 PM
could be two things.  You may have mismatched idle mixture screws.  I've seen different tapers thu the years. And/or, the idle discharge hole may not be the same size on both sides.  I've seen it on virgin carbs.  Have you measured both sides idle discharge holes ?
Title: Re: Idle Mixture Screws
Post by: 59bluesilver on September 22, 2016, 12:20:38 PM
The screws are the same length as is the springs.
Title: Re: Idle Mixture Screws
Post by: Jeffs68 on September 22, 2016, 01:19:13 PM
I don't think it matters. When you are making your adjustments, turn each one in, one at a time until the engine starts to run rough and Revs drop, then back it out 1/2 to full turn. You can use a vacuum gauge to assist, make adjustments that will give you the most vacuum possible.
Title: Re: Idle Mixture Screws
Post by: 59bluesilver on September 23, 2016, 06:45:54 AM
I guess I don't understand what the taper does or its function. There must be some reason why it extends into the Venturi, or not. Can someone explain it to me?
Title: Re: Idle Mixture Screws
Post by: Jeffs68 on September 23, 2016, 07:26:35 AM
That additional air bypass hole may have something to do with it?
Title: Re: Idle Mixture Screws
Post by: 59bluesilver on September 23, 2016, 09:21:32 AM
I guess, it's the only thing that makes sense.