Q-Jet Idle Circuit

I've got a 71' 350 4V GS with a Q-Jet. I rebuilt it several weeks ago and it was running better than I could have hoped for....until last weekend. At idle it runs like crap ! Off idle and under acceleration it is strong as ever. I am suspecting one of the idle circuits has stopped functioning.

My question: Is it possible to remove the mixture screw and spray some cleaner "in the hole" or am I better off to buy another kit and go through it? When I had it apart it was clean as a whistle and I put a new filter in. Any other suggestions?

Thanks

Scott

 

Injecting aerosol carb spray into the idle mixture screw hole is a very good idea. Assure that you get some spray coming out of the idle air bleed, too.

 

You shouldn't need another kit, but I'd open it back up and see what you've got in the bowl. Sounds like you have some trash in there blocking the circuit. Spraying cleaner in the idle screw hole should clear it, but you'll need to make sure there's not some more trash to plug it again. With any carb, cleanliness IS godliness! :Smarty:

Be careful not to overtighten things when you put it back together, you don't want to warp the airhorn - just beyond snug should be fine, especially on the carb-to-manifold bolts.

 

If the idle passage is blocked, you will get an unusual condition where some of the cylinders will fire, and some will not. The pattern will be unusual, such as 1,4,6,7 or 2,3,5,8 not firing. This is due to the crossfiring of the dual plane intake manifold. If this is the problem, it will affect off-idle as well, to some degree. Let me know... Ray

 

I found my problem. Its not real "cool" to admit your ugliest of screw-ups but I share in the interest of helping others ! o No:

A couple of weeks ago, I was replacing the air cleaner hold-down stud. I kept putting it into the hole and couldn't get it to "thread" properly. I then noticed I had it it the forward hole or bowl vent instead of the properly threaded hole intended for the stud ! ! ! :eek2:

I then assembled the stud, housing and hold down wing nut. The following "pleasure rides" showed something was wrong. Guess what is right below the bowl vent hole? Yup, the float ! ! I had managed to bore a nice hole in the phenolic float filling the bowl with "phenolic pieces". OUCH ! ou: ou: ou: ou: ou: ou: :jd:

So, off with the carb ! I cleaned it all out and made sure all the passages and etc. were clean and installed a new float and gaskets. Amazing how much better it runs without all that trash in there !!

Well, lesson learned...... :Smarty: If you stick it in the wrong hole, it'll make a real mess ! ! :shock:

 

:laugh: !!! Not gonna touch that one...but glad you found the problem. I've tried to put that stud in the vent before, I think everybody has at least once. :bglasses: