I'm trying figure out the process of adjusting the air/fuel mixture screws on my 81. I've watched several videos but one part of the process has got me stumped. I've got the dwell meter and 2 adjustments tools. My question is you're adjusting 2 screws with the target 30 on the 6 cylinder scale on the meter. How do you get one adjustment close to 30 then the other adjust to 30,do you adjust one side close to 30 then adjust the other side until it comes up to 30,providing both adjustments are off? Right now the settings are both screws turned out 3 complete turns. My apologies for asking the same question that's been answered before,I can't seem to find the correct info here. Any tips,help would be greatly appreciated.

 

Well Z51JEFF I've been looking for the same procedure myself so stay tuned as there will be a lot of info from the forum
experts!!!

JJ78

 

Evidently the experts are on vacation😁 I've pretty much got it figured out after watching videos and gathering information from a number of places. I've got the dwell meter and 2 carburetor adjustment tools with the Double D sockets. After running down a vacuum leak I've got the car running a lot better. The adjustment on the air/fuel screws are:Turn both screws in until they stop,not tightened. A base setting would be turn both screws out 3 turns to start with. There is a GREEN plug not hooked up to anything in the area of the base of the carburetor,this is the diagnostic link to the computer. With a dwell meter positive hooked to this GREEN PLUG,negative lead of the dwell meter hooked to the negative to the battery. With the car warmed up,running in closed loop,the setting on the dwell meter in the 6 cylinder scale the target is close to 30. There are other more extensive adjustments but I'm only tooling to get the air/fuel mixture correct. Now these 2 adjustment screws area sealed from the factory,the carburetor needs to come off the car to remove these plugs. These 2 adjustment screws are a pain in the *** to get to but it's possible. The reading on my car when I checked was around 25. I'll adjust these when I get some time. My question is how do you get the reading of 30 when you have 2 screws,I'm assuming turn both out,in at the same time.

 

you need to measure the travel of the paddle that controls the metering rods to keep it at 4/32" plus there is a tool to adjust the idle mixture big screw in the top to keep it in sinc with the 2 screws that are used to adjust the cruise mixture. I hope this helps

 

Those are sealed from the manufacturer before they are ever installed on a car, the procedure is remove the plugs and count how many turns "in" until it stops and then re install them the same way the factory installed them, If all the bleeds and carb is all clean the air mixture screws shouldn't need adjusted provided you set everything adjustable correctly. When everything is set right the Oxygen sensor will cycle rich/lean about 4 times a second on a lab scope which is what makes the 3 way catalytic converter active, It's all about exciting the catalytic converter and while this carb will cycle rich/lean around 4 times a second the fuel injection that replaced it can cycle rich/lean around 30 times or more a second which really makes the Cat work compared to the 4 times a second of a carburetor, if I remember right those carbs mixture screws were around 4 turns out

 

With your vacuum gauge get the two screws at the base set to give you the highest vacuum. Then set the large air bleed screw on the top or get the dwell to consistent 30 degrees dwell. You will find the best combination of settings will result in the large air bleed screw being about 2 threads down, maybe 3 at max. If it is screwed down further than that you have either a vacuum leak or something else not set correctly on the carb.

Good luck, I spent many hours going down the correct procedures until I got the carb set and all vacuum leaks fixed. But once all is set up correctly you will not need to touch again. The CCC will take care of everything from there. Also, I would recommend getting a 1981 Corvette shop manual, it has all the correct procedures and trouble shooting flow charts to get you on the right track.

Keep at it, you will be happy afterwards.