Need a lil q-jet help!!

[Telecasterjoey]

Hey all, do I've got my q-jet apart I have a pretty good understanding of how it works and what to fix but the last carb I opened up was slightly different than this one. I need to know what this needle looking part is and what to adjust it to.

Carb no.*17086248 it's off and 86 c10 with a 305 (now 350)

The hole for the needle is between the float ceet hole and the primary metering rod holders hole. There are 3 holes in a row at the front of the carb. They are shown in pic 13 in this link:

http://www.hemmings.com/mus/stories/...feature20.html

The black plastic piece that holds down the float has a hole in it to adjust this needle.

The needle looks like one of the air mixture ones for the base of the carb but the end is dull and not tapered, it also has a spring.

Also if anyone knows what to set my float height to that would be great, my instructions don't say!


Any help would greatly be appreciated.
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[Telecasterjoey]

Bump!!
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[GruntMoanCough]

Here's a bunch of info that should keep you outta trouble for a while...

http://www.florida4x4.com/tech/quadrajet/

[jrblanke]

Have you checked your rebuild kit for this information? Ususally they have the specs to what everything needs to be set to.

[Restrorob]

That adjust the depth of the low speed metering rods in the low speed jets, If it's adjusted too far out (metering rods further out of the jets) it richens the circuit causing rich smelling exhaust. Too far in will lean the circuit and cause a hesitation on acceleration.

There's a aluminum plug in the top of the carb right above this adjuster, You can carefully tap the plug out then re-assemble. Once the carb is back on and engine running, With a tach and vacuum gauge hooked up this can be adjusted with the same tool used to adjust the front adjusters while running.

Adjust to maximum engine idle RPM and vacuum, It may take a few times going between the front and top adjusters. I haven't seen one set adjustment like X turns out, The above method adjust the carb to each individual engine.....

[classicgm]

Its called an APT (adjustable part throttle) and its for fine tuning the cruise AFR. The only accurate way I know of to tune it is on a load bearing dyno with o2 and vacuume gauge. Otherwise, start driving and adjusting until you get max vacuume reading at cruise. IIRC the starting point is 2.5 turns out but don't quote me.
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[Telecasterjoey]

Thanks for the responses guys! Glad I finally know what part it is lol, does anyone have any pics of the air horn mod to make the Apt accessible from the outside?
I'd like to do this to get the most performance outta my carb!

Thanks again for the help!
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[Telecasterjoey]

Welp got her buttoned up and the truck fired up right away, it was a little late to be revving up the truck in my neighbourhood but it idles pretty high and the idle screw is all the way out. The choke is 100% wide open and the choke pulloff is pulled in how do I get this sucker to come down a bit? The mixture screws are at 2 turns out and the apt is at 3 turns out.....

should I pull it apart again and lean out the apt or can I get the idle down with the mixture screws?

[tater502]

Originally Posted by Telecasterjoey

Welp got her buttoned up and the truck fired up right away, it was a little late to be revving up the truck in my neighbourhood but it idles pretty high and the idle screw is all the way out. The choke is 100% wide open and the choke pulloff is pulled in how do I get this sucker to come down a bit? The mixture screws are at 2 turns out and the apt is at 3 turns out.....

should I pull it apart again and lean out the apt or can I get the idle down with the mixture screws?

Check this out.. http://rmcavoy.freeshell.org/Q_Jet_bushings.html

[Telecasterjoey]

That's probably what the problem is lol I was kind of afraid of that from the beginning! That's a great link, does anyone know where I can a sheet of Teflon???

Thanks for all the help!

[ray_mcavoy]

Originally Posted by Telecasterjoey

That's a great link, does anyone know where I can a sheet of Teflon???

Thanks ... that's my website Although credit for the idea goes to fellow member HEI451.

I've heard that you can get the teflon sheet at many hobby/craft stores but I couldn't find any locally. So as I mentioned in that write-up on my website, I bought some from www.smallparts.com I noticed that the link now re-directs to www.amazonsupply.com but it appears as though they're still offering the same items.

The part number I bought a few years ago from the old smallparts.com site was STE-0015-A for a 6" x 6" x .015" sheet. Looks like the closest thing they offer now is a larger 6" x 12" x .015" sheet under the new ASIN (Amazon Standard Item Number) of B000FPC3TG.

[bilfman]

Well I will put in my few cents here. I have had gm products for over 25 years and do love the q jet. However they can be a bear to get working properly once they give er up. They are fantastic when they work and frustrating when they don't. I recently had my q-jet giving me grief on my big block. A master mechanic buddy of mine suggested I try an edelbrock. I put on a 750cfm 1411 carb and am totally impressed with it. Install was easy, all stock components work and it is so simple to dial in. The truck has great power, the 4bbl works wonderfully and starts cold like a fuel injected unit. I can just touch the key and walk away.

As much as I love the q-jet I don't think I can ever go back.

[classicgm]

I like the no drill throttle shaft fix. nice work. link added to florida4x4

I still prefer drilling and bushing, but you have to have a drill press to get it right. nice to see there is another way