quadajet mixture screws adjusting / fuel line fitting sealer? - Team Camaro Tech
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post #1 of 5 (permalink) Old May 22nd, 02, 12:48 PM Thread Starter
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for a 1974 firebird with 400 4bbl engine/automatic,I just got the 4bbl quadrajet rebuilt & after installing & running warmed up,
do I need to turn the 2 mixture screws AT THE SAME TIME inward till the engine slows down & back them out 1/4 turn? Or is there a better procedure? Only thing is I would think both screws are not positioned the same after a rebuild!
Also, the pesky STOCK fuel line’s fitting that screws onto the carburetor's fuel inlet –I know that will leak unless I use some kind of sealant:Some say to use teflon tape, but others say gasoline will break down the tape.
Or I could use permatex gasket/sealer in a tube (the goey stuff that dries hard), but I heard that might be drawn into the carb & get into small passages. Any ideas?
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post #2 of 5 (permalink) Old May 22nd, 02, 01:44 PM
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You start with a "bench" setting on the idle mixture screws - turn them in lightly to seat, and back them out about 1-1/2 turns. Fire it up and put a vacuum gauge on a manifold vacuum source, and turn the screws individually, working back and forth between the two of them, about 1/8-turn at a time until you get the highest steady vacuum reading (you'll have to tweak the idle speed as you go along, as it will change).

No "sealer" is necessary on the fuel inlet fitting - it seals at the flare at the end of the tube, not in the threads. A little bit of teflon paste or anti-seize on the threads will help get a good mechanical seal at the flare by reducing thread friction or galling as you tighten the flare nut.

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post #3 of 5 (permalink) Old May 22nd, 02, 02:29 PM
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If you are talking about the fitting that the line screws into in the carb. (that holds the Filter in) there is a plastic seal ring (comes in the rebuild kit) that is installed on the end just below the threads on this fitting. This seal bottoms in the carb and seals the fuel. I would not recommend usin any sealant such as Permatex #2 (soft) here but, I have put a wrap of Fuel Resistant (Yellow) Teflon Tape on these if they show signs of a slight leak.
I do not put tape or sealers on the flared fuel line fittings.
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post #4 of 5 (permalink) Old May 22nd, 02, 08:01 PM
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John, I've seen teflon tape on many GM cars with quadrajet, it's on the inlet fuel line flare nut.
I don't see what this does as the flare seat seals the fitting.
Any comments??

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post #5 of 5 (permalink) Old May 23rd, 02, 07:56 AM
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I have seen it also, mainly on trucks.
The only input I would have would be it's ability to prevent the galling of the carb. fitting threads if the material is softer than the flare nut or to prevent corrosion between the two fittings in extreme (like back east!) climates with road coating issues.
It is the oil resistant (light yellow color) type like used in other truck, tractor hydralics and some automotive applications.
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