Quadrajet Float Adjustment - Pontiac GTO Forum
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post #1 of 6 (permalink) Old 08-27-2019, 09:36 AM Thread Starter
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Quadrajet Float Adjustment

Super easy question (for you guys!)

I need to adjust my float level - I've had flooding issues on a hard stop a few times, and pretty sure a high set point is the cause. I'm familiar with this carburetor (1968 original) from rebuilding as a kid, but my question is, Do I need to fully remove the carburetor just to set the float level, or can I just remove the top to make this adjustment? Of course I get nervous about dropping the small bolts inside the primary down, but suppose a mag screwdriver would help that.

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post #2 of 6 (permalink) Old 08-27-2019, 04:04 PM
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Have seen several guys remove just the top, at race tracks, to make changes.
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post #3 of 6 (permalink) Old 08-27-2019, 08:04 PM
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Yep, you should be able to pull the top. Remove all the linkage rods first.

Your accelerator linkage most likely does not have a spring clip holding it on - early carbs did. So you will need to knock the accelerator lever pin in towards the carb body to release the accelerator lever so you can free it from the linkage rod.

Use a small diameter pin punch or even a finish nail with the end ground flat. It MUST be no larger than the pin or you will not be able to knock it through. Gently tap it in, but just far enough to free the accelerator lever so you can remove it.

To reinstall, make sure the linkage rod is in the highest hole. Insert the accelerator lever and with a small, flat bladed screw driver, gently pry the pin back through the hole in the accelerator lever and carb ears. DO NOT force it. if you break off one of the casting ears that holds the pin, the carb is basically toast. It should slide fairly easy back through the hole. If not, the accelerator lever might be slightly off, so wiggle it into position.

Two small screws are often missed in the primary barrel of the carb. Open the choke fully and look down inside, you will see them. Have the carb throttle blades closed just in case you drop 'em. I like a magnetized screw driver for this.

I typically remove the secondary hanger and rods - makes it easier when putting the top back on as you install these after the top is on. You will see that tiny screw on the hanger. The hanger rides on a plastic cam. Inspect it to make sure it looks good. You can replace it IF needed. https://quadrajetparts.com/quadrajet..****e-p-170.html

Good time to replace the needle and seat to make sure you have ethanol gas friendly parts. They come in different sizes to allow greater fuel flow. The .115" should work fine for street use. As you go bigger, the float may not be able to apply enough pressure onto the needle to over come the fuel pressure - should it be higher than stock. This is where you can get flooding and a pressure regulator may be needed. Use a wide flat bladed screw diver that fits snug in the seat slots. If you use a small blade and don't catch both side of the slot, you may simply twist away and not do anything other than damage/distort the seat slot. You will eventually get it out, but remember, you have to insert the new seat and damaging it may cause issues. https://quadrajetparts.com/needle-se...ed-p-2045.html

If the carb still has its original Nitrophyl float, I suggest the brass float replacement. The nitrophly float can over time absorb gas and become heavy - and this will affect float level settings. Just make sure you get one that is the same as yours, they have different lengths. https://quadrajetparts.com/quadrajet...-c-128_21.html

Next, get a new accelerator pump. These too go bad and you want ethanol friendly. https://quadrajetparts.com/quadrajet...2132-p-33.html

Finally, get the correct top gasket. There are a couple different ones. Use the vertical carb number found on the side of the bowl to make sure you order the correct application for your carb.

You can buy a carb kit, but it will not have the float and may or may not include the accelerator pump complete, and it will have parts you won't use at this time. So you can decide how you want to go about doing your adjustments. If me, and because I had the top off, I would do some parts replacing.

I have never used the vendor I have shown. I used them for reference so you can see what I am talking about. There are many sellers for Q-jet parts, so who you select is your choice.
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post #4 of 6 (permalink) Old 08-27-2019, 08:53 PM Thread Starter
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Awesome, thank you Jim so much for taking the time to respond at such length! I appreciate everything. Funny thing is Iím told this carb was rebuilt recently, but Iím convinced from another thread you helped me on as well that my float level is high, causing two stalls now when hard decelling. So I hope to not have to replace anything this time, just get my float to the proper level. Even so, all your tips are amazing and I appreciate it, I will follow them. Thank you!
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post #5 of 6 (permalink) Old 08-27-2019, 08:54 PM Thread Starter
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Btw, I know from the carb number itís a genuine 1968 carb, for what itís worth.....
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post #6 of 6 (permalink) Old 09-16-2019, 01:19 PM
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Excellent write up by Jim, as usual. I'll add that you need to fiddle a bit to get the choke rod back through the hole on the arm at the bottom of it's well...you can't see it and it has to be done by feel. If you can unscrew the choke rod cam at the choke plate, do that, and be careful not to bump the choke rod out of place on the lower cam.....I'm pretty good at fiddling them back on, but I've done a ton of them over the years. Be sure to let the metering rods hang straight down when you lower the carb top back onto the carb body so that they don't hang up. At this same time, guide the accelerator pump through it's hole and you will be good to go. Take your time and watch the screws and clips......I just did this on a '71 Corvette for a friend's cousin 2 weeks ago and it worked out fine. Did it a BUNCH back in the '80's when I worked in the industry doing tune up work. It looks harder than it actually is.
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