abrasv

So I'm trying to adjust the Q-jet and set the timing. Just installed a Pertronix and starts right up. When going to adjust the carb needles by using a vacuum gauge plugged into the bottom front small vacuum port on the carb I get no vacuum at all from that lower port. No suction at all.but yet when the dist. is hooked up to that port it works but it isn't providing vacuum. I hooked the gauge up to a port on the intake manifold and the gauge works as it should. Why am I not getting vacuum from that from carb port?
How would you folks suggest setting the carb other then using vacuum?
Sorry, should have mentioned this is on a '69 Cutlass 350.

dc2x4drvr

Use your manifold port, not the carb to dist fitting. With that said, on a new carb, I start with the needles out around 2 1/2 to 3 turns, then start and observe the vacuum reading..

rocketraider

No vacuum at that port because it is ABOVE the throttle plates. Once the plates open above idle, you will then have vacuum at that port. It's called... PORTED VACUUM! and is useful for distributor advance because you don't want vacuum advance at idle.

Use manifold vacuum to set carb idle mixture. Set it to get highest vacuum reading at idle speed, then turn screws in, alternately and equally about 1/8 turn at a time, until idle speed drops about 50 rpm and that's a good baseline idle for your engine.

Fun71

That subject has been debated quite a bit, and which vacuum source is used can vary depending upon the specific engine setup and the desired operation.