Basic Q-jet idle adjustment

GT6Steve

GT6Steve

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Joined
Jul 13, 2008
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Las Vegas Nevada
I've been looking a through the books and archives but this is too basic a question to be answered.

Assuming all is good in the carb and/or freshly rebuilt.

Would I adjust the idle mixture by opening the idle screws one at a time until maximum RPM is reached then back it off a half a turn?

If so, do I do one side ata time or both back and forth alternately?


The SMOG Bitch screwed up the car so bad it'll not even run smoothly now.

Thanx in advance, Steve

And one more thing, is that idle screw tool readily available?
 
Steve, I used to have one of those tools at one time. I'm sure I still have it but not sure where. If I run across I will let you know.

I'm relatively sure that it's not too different from a Holley, screw both in until it starts to stumble, then back out 1/2 turn. But I'm no Lars.
 
Start by running both screws in to lightly seat them, then back them out 1-1/2 turns. start it, warm it up and adjust them evenly for best idle. Make sure the throttle plates are closed as much as possible. Open too much and you get into the transition and main metering circuits. Should get you close. You can plug in a vacuum gauge and adjust for best (highest) vacuum too. Just be sure and use a full vacuum port. Trying to adjust using a timed port gets things kind of silly.
 
Thanx all for that. It's a bit different than Webers but I get what was said. Is there a readily avaible tool to get under the mess at the front of the carb? I've got a right angle remote screwdriver for slotted head screws. Will NAPA have the same thing for these weird ones?

I'll do a google....
 
Hey Steve, you have a lot of experience with Webers? I'll need your expertise with a pair of Webers I just got for my 240 track car. Maybe when you come over and pick up that air cleaner, you can give me some pointers.
 
GT6Steve said:
Thanx all for that. It's a bit different than Webers but I get what was said. Is there a readily avaible tool to get under the mess at the front of the carb? I've got a right angle remote screwdriver for slotted head screws. Will NAPA have the same thing for these weird ones?

I'll do a google....
Click to expand...

I've got an old adjuster from Snapon that is roughly a curved 45° end and about afoot or so long. It takes any 1/4" drive socket. Has a knob on the other end that is marked, so you know how much you turned it. Also have an old Herbrand carb tool set in a steel box that has all the air mixture ends, gauges, flats with a collar, hex, allen and the oddball ovals.
 
I used a vacuum gauge attached to manifold vacuum port. You can see the gauge needle bounce. I adjust both sides little by little to reduce the bounce and get high vacuum. Less bounce is smoother idle.

The tool I bought a number of years ago came with several Adjuster tips (slotted, hex, Allen etc...). The tips attached at one end and the tool used what looks like heavy speedo cable for the shaft so its flexible.
 
Last edited:
daveL82 said:
The tool I bought a number of years ago came with several Adjuster tips (slotted, hex, Allen etc...). The tips attached at one end and the tool used what looks like heavy speedo cable for the shaft so its flexible.
Click to expand...
Same one I have/had. I bought it specifically to adjust Q-jets. I've been looking for it for a year now and can't find the damn thing. I know I didn't get rid of it.
 
I just bought that unit this morning. Seems to be working OK if I can secure the snap in clip better.

I'm playing with the idle screws just now. It doesn't want to idle at all. Just slowly idles down until it stalls. Just barely got started on it. If all else fails I can put the old carb back on.....
 
Also one idle jet could have gotten plugged. May have to remove the mixture screws and spray carb cleaner in the port
 
I've got it up at the nasty Queen bitch shop just now. I got it to run nicely with 3-4 turns out on the idle hets. Seems wrong to me. Then it was burbling at parial thottle which suggests the needle height is wrong, presumably the centr screw which looked way too high to my eye.

All I need is for the Queen to get it to SMOG and I can make it run aferwards.
 
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