Is this port on the driver's side base plate supposed to be timed vacuum or manifold? It looks like it's supposed to be manifold to me. I get 0 vacuum at idle and only start to get a vacuum reading with increased throttle. I get 14" from a port directly on the manifold.
Also my advance canister says "16" but when hooked up it adds 33°. Whether it has the stiffest springs or weakest springs installed it's the same result. I've read of other cans doing this and installing a limiter fixed it. Are there manufacturing defects that add more timing than stated on the can?
Thanks.

 

There are advance cans with replaceable springs? Whoa. Sometimes there's a screw inside the nipple that turns to set a stroke limit. I'd definitely try a different can.
That particular port is usually for the gas vapor canister. It's a restricted port, should have a very small hole. I always thought it was manifold, but it's going to that U-shaped channel which goes to the vertical slots in the base plate which might be going to the vertical transition slots or the ported vacuum hole which is right above the transition slots. It's been a while, and I'm too lazy to walk out to the garage.

 

Manifold vacuum off the carb is really only possible on the throttle plate, so you're correct to make that deduction, but not everything there has to be manifold, like Oddball said. The manifold ports I see on the carbs are usually on the back, and they're usually for power brakes.

 

Thanks. I was hoping I didn't just have a bad vacuum leak that was killing the vacuum in that spot. I can never get the starter fluid test to work as the vapors are sucked into the intake and increases the rpm no matter how I do it. I can visually see the vapors being sucked into the top with the filter on or off. I'd need to make something like a cold air intake type of tube to stop that from happening.
The distributor springs. Just heading off the inevitable "your springs are too weak so the mechanical advance is kicking in when the rpms increase from hooking the vacuum advance back up."

 

Which is the definition of ported vacuum.

 

Correct me if I'm wrong, and I'm nearly always wrong, but I always thought you could tell what kind of port it is on a carburetor by where the port is, vertically. Those ports up high are ported vacuum. Those down low, near the manifold, are manifold vacuum.

I've labeled them in these two photos. The first photo is the front of the carburetor.





This is the rear of the carburetor. The lower port is often used for the power brakes, while the upper one is usually connected to the choke.





Again, if I'm wrong about this assumption, please let me know.

 

Correct me if I'm wrong, and I'm nearly always wrong, but I always thought you could tell what kind of port it is on a carburetor by where the port is, vertically. Those ports up high are ported vacuum. Those down low, near the manifold, are manifold vacuum. I've noticed that none of the ports is ever in the "middle."

In the first photo at the top of this thread, we can't tell what kind of vacuum is at the port circled in red because we're looking at the carburetor from the bottom. We need to see it edge on.

I've labeled them in these two photos. The first photo is the front of the carburetor.





This is the rear of the carburetor. The lower port is often used for the power brakes, while the upper one is usually connected to the choke.





Again, if I'm wrong about this assumption, please let me know.

 

From this crew???

Seriously, no, unfortunately that is not correct. For example, that port at the top rear of the car has nothing to do with vacuum. It's actually the clean air feed to the hot air choke. Keep in mind that the choke works by pulling heated air past the bimetallic coil in the choke housing. That heated air eventually goes into the intake (via the vacuum port inside the choke housing), so you want clean air to start with. This port is just a source of clean air and has no vacuum at all. Similarly, the large port high on the front of the carb is the bowl vent to the charcoal cannister, so again, not a vacuum port. The others may or may not be manifold, ported, or timed, depending on the use. And of course the ports on a Qjet are different from the ones on a Holley are different from the ones on an E-brock.

 

Cool! Thanks.