What is the procedure for setting the air/fuel mixture using a vacuum gauge?
 

Can anyone explain the procedure for setting air/fuel with a vacuum guage? I've never done it this way but I've heard it mentioned in the forums.

Thanks.

It's pretty simple. Get the enigne warmed up/choke off. At idle in neutral hook the gauge to a full time vacuum port using a tee. Adjust each idle mixture screw very slowly to max vacuum. You may want to go back and forth a rew times to get it maxed out. Some people will also do it again in gear with someone holding the brake if you have an automatic.

i'm just curious, what does it change when you have the truck in gear.

Thank you
 

Thank you Gentlemen. I appreciate the help.

it places a load against the motor and therefore drops the idle speed- affecting the vacuum reading at the same time..

Set the number of turns on the air / fuel mixture screws evenly. Such as 3 1/4 turn set out on each a/f screw, while maintaining the highest vacuum reading possible.

The highest vacuum method works for the most part but it may not be optimal for driveability. You may need to go slightly rich. -Just my 2¢

By "slightly rich" do you mean 1/4 turn out...1/2 turn out?

Rev your engine and check for a dead spot on the acceleration, then go out a 1/4 turn if you feel the engine should needs it, rev the engine and check if the engine response has improved.