How to Adjust Carb with Air Screw

[EngineerDoug]

Hello all,

I have a 4160 Holley, list 3918 from '68 on my 383. I rebuilt the carb and have it running on the motor. This carb was used on 440's and has an adjustable air screw. The amount of airflow is adjusted by turning a screw just adjacent to the primary bowl vent tube. It provides some airflow below the throttle blades at idle.

My question is, does anybody have any experience adjusting a carburetor with this system? I am not sure how the various adjustments should be made - idle mixture screws, primary throttle blade position, and this airflow screw. I know you want the primary throttle blades so that the transfer slots are just uncovered, but wonder about the other two degrees of freedom.

Thanks.

 

[lewtot184]

i've never messed with the holley mopar smog carbs with an air screw but have played with them on the carter avs's. pretty sure the principal would be the seem. they introduce air in the gasoline to help meet a/f ratios. truth is you can probably close it off and just use the mixture screws in the metering block (if they are there). i just use the air screw for fine tuning on my avs,

 

[Pops1967GTX]

Holley Tune, Part 1

 

[Jcharger]

I am not familiar with this adjustment and don't see it described in my 1970 FSM. Do you have a picture of the adjuster screw. Maybe it can be found by looking at the FSM for 1968.

 

[Pops1967GTX]

Page 9 4160 carb adjustment...
1968 Chrysler Imperial Carburetor Service And Repair Highlights from the Master Technicians Service Conference Session 243


1967 Chrysler Imperial Holley Four-Barrel Carburetor Repair fom the Master Technicians Service Conference Session 235

 

[HEMI-ITIS]

Use a vacume gauge.Turn screw in 'till is starts to stumble and you will see the vacume get lower,now open untill you gat max vacume.Do the same to both screws.

 

[EngineerDoug]

The Master Technicians Guides hit the nail on the head; thanks a bunch!