[VWNate1]

To use a vacuum gauge to adjust the carby ;

First you *must* have the timing set properly to 0° ~ 6° BTDC @ idle of 700 RPM's or less , then insure the spark plugs are gapped to at least .040" (.060" if HEI) and the center electrode's shoulders are sharply squared off , if they're rounded it'll loose power .

Connect the vacuum gauge to the port below the carby so it has a constant vacuum signal , start and warm up the engine fully .

Set the idle speed to 1,000 RPM and s - l - o - w - l - y turn the idle mixture screw in as you keep an eagle eye on the vacuum gauge ~ in time it will begin to rise , as you get the screw further in the gauge's needle will begin to flicker and if you turn it in further the engine will begin to shake and miss ~

Gently play with it to get a feel for how the needle responds to your fiddling with the mixture screw and then turn it to where the needle gets it's highest , steady reading , then back it out maybe a 1/16th of a turn and let it idle longer while you blow on your seriously burned fingers , I have no idea why the hell GM put the ding-dang mixture screw right there where it's easy to see but hard to access ~ I have a 3' long 1/8" flat bladed screw driver I use for just this job, gotta watch out the back end of the screw driver doesn't get caught in the P.S. belt .

To recap : adjust the carby's mixture screw to get the gauge's highest _steady_ reading then back it off a tiny fraction and you're good to go ~ you can then fiddle the idle speed to suit if you want , 600 ~ 1,000 is the desired hot idle speed .

Once the mixture is set and the idle speed is adjusted , do not touch the mixture screw again .

If it stalls when cold started , the fast idle speed is adjusted by gently bending the vertical rod from the choke plate downwards , when the throttle is held open ~ at the bottom of the rod is a stepped fast idle plate that lifts as you gently bend the rod using two pairs of pliers ONLY AT THE PROVIDED BENDS ~ a little bit will do , don't be a jerk and pretzel the rod like Gas Station idiots do as they're impossible to find once you've ruined them .

It's is critical that the stepped fast idle cam thing toches nothing when the choke is fully open ! .

I hope this helps .