i have a 1974 d200 w/ 318 engine and a simple carter 2bbl bbd carb. the large rear vacuum port has no vacuum at idle. is this normal and if so what is the best way to adjust mixture with a vacuum guage? if NOT normal, what is the fix on the carb.

 

Not sure about the large port . When adjusting mixture with vac gauge both screws should be approx the same number of turns out , Adjust to highest vac reading . may have to go back and forth a few times . I usually check ignition timing first before adjusting carb . Timing is a large factor in engine vacuum .

 

where should i hook up the vac gauge if there is no vac at the rear of the carb? thanks for the reply

 

Any port that has vacuum at idle will work .