Carter AFB carb vacuum port question

[Ken47]

Hi. I am wondering in anyone on here can help explain the vacuum ports on the Carter carb I have. It is a Competition Series 9635SA carb. It’s 625 CFM. It’s new (ie not used before). It’s about 20 years old.
When I put the vacuum gauge on the drivers side port I get no vacuum reading at idle. Everything I have read online is that there should be full manifold vacuum there. I understand that I should hook up the distributor vacuum advance to full manifold vacuum (not ported). However when I crack the throttle open it instantly shows manifold vacuum on the driver’s side port. The passenger side port shows about 5” Hg at idle.
Is this the way it is supposed to be? I have read that the Carter carb is that way and have read that it isn’t i.e.it’s the same as an Edelbrock. If it is operating as it is supposed to, what kind of timing set up would suit that mode of operation?

 

[enjenjo]

The passenger side should show manifold vacuum at idle, the drivers side is ported vacuum and is above the throttle blade. If you are showing low vacuum at idle on the right side, run some cleaner through the passages, you might even blow some air through it.

 

[Ken47]

I found a fellow here in Calgary that helped tune the carb and ignition timing. He adjusted the accelerator pump on the carb (more volume). Adjusted the idle mixture, changed springs in the mechanical advance (advance in sooner), connected vacuum advance to ported side (passenger), set the idle speed (raised it). I had the initial and total timing set ok so that stayed the same. On a test run at 100 km/h the engine runs good but there is a significant vibration which looks like incorrect driveshaft U joint angles. Tomorrow it’s off to a driveline shop to see if three is an easy (cheap) fix. The angle problem is a direct result of not having the full car weight on the chassis when I set it up. Oh well, live and learn

 

[enjenjo]

The passenger side should show manifold vacuum at idle, the drivers side is ported vacuum and is above the throttle blade. If you are showing low vacuum at idle on the right side, run some cleaner through the passages, you might even blow some air through it.

I mis-spoke, the drivers side is manifold vacuum. The ported vacuum is used on emission controlled engines, Manifold vacuum for non-emission engines. If you have a heating issue at idle, manifold vacuum may clear it up.

 

[fraso]

If you're not sure, take the carb off and spray some carb cleaner in each vacuum nozzle. That'll clean out any crud and you'll see exactly the source of the nozzle's vacuum.

For a car with an automatic transmission, I find that using ported vacuum gives smoother transition from park/neutral into drive.