Hi folks, I got this truck about a month ago and I think I want to try to stick with the Nikki carb but I would like to play with the mixture. I see 3 places that look like they might be concealment plugs, and there is one thing on the valve cover side of the carb that might have a screw under it (it moves but wont come off). I'm sure if I pull the carb off I can find it, but thought I'd see if anybody can give me some guidance first. Thanks in advance!

 

I haven't messed with one of the earlier Nikki carbs.....not sure if they were a "feedback" design or not......meaning there would be a computer/ECU that controls idle mixtures.

 

I dont see an o2 sensor or a computer on this truck. Also, on the feedback quadrajets I have seen, there are still mixture screws. It's weird how there seems to be hardly anything on the internet about that carburetor. I even found a $9 haynes book on ebay and bought it and it had no procedures for carb overhaul, adjustment, testing, etc etc. I'm leaning towards just getting the repair kit from rockauto and rebuilding it. Pretty sure I'll find the hidden screw when I get that carb on the table.

 

Ok.....it should not be a feedback type carb then. That said, I would go the rebuild way myself also.

Yes, even the 1986-1993 B-truck carbs that are computer controlled, have a mixture screw on them......with a roll pin inserted in front of them so you can't adjust it......unless you remove the carb and hammer out the roll pin.

 

I'm not sure what the third screw is you're talking about, but the mixture screw is the brass double-flathead one in the aluminum sheath.

 

View from the passenger/valve cover side.

In red is the mixture screw, green (not visible, below the solenoid and in the base of the carb) is the idle speed screw, and blue controls how much fuel the throttle pump squirts out.

Pink, I believe, controls idle when the AC is running. My 84 doesn't have AC, so that's just a guess.