idle issues and poor vacuum

[tone]

Hey folks - I've got a 64 cuda with a 273 and I'm having some idling issues with the car. When I first got the car, I had a mechanic give it a tune up - he got it running smoother (replaced the points and set the timing - to what, I'm not entirely sure), but there still appears to be some sort of vacuum leak, as it won't idle without the choke partially closed off.

The vacuum line from the distributor is split off to 2 ports on the carburetor - one on the side and one on the rear, where I'm guessing an automatic choke diaphragm was once hooked up (it's got a manual choke right now). If I put the gauge inline with the distributor hookup, I get a steady 5 in. .. if I put it inline coming off the distributor, it reads more like 9 in. (going off the top of my head). I've been unable to find any vacuum leaks - Ive used a can of starter fluid around the base of the carb as well as the intake manifold, but didn't notice any idle difference with the spray anywhere. When it's running, it does have a sucking sound but I'm guessing that's normal with the air filter off.

Another thing I don't understand is the fast idle cam - on the carb, it doesn't appear to be hooked up to anything... is this because it was converted to a manual choke?

Any ideas on what I should start troubleshooting? I don't have an awesome understanding of carburetors and how to adjust/fix them.

 

[tone]

Pinching off the vacuum advance on the distributor seems to jump the vacuum up a few inches as well. Any takers?

I don't know whether it's worth pulling the carb off and doing a rebuild or not, given that the poor idle might be related to the low vacuum.

 

[tone]

Well, since the recent posts were lost, I'll add more information again and repost the images.

I've put the vacuum gauge on both (at different times) the distributor advance port (on passengers side of carb) and on the manifold vacuum port on the back bottom of the carb and get the same readings - which confuses the hell out of me, since I've been told that the distributor advance port is ported/vented and shouldn't be pulling vacuum at idle... plugged off both ports and plugged up the PCV port and it was getting between 16-17in of vacuum, which seems reasonable. With everything plugged up, I got it idling without the choke involved (a little rough but still idles) by setting the mixture screws 1.5 out from base and setting the idle.

Anyone have any ideas why I'm getting vacuum on both the distributor advance port and the manifold vacuum port on the carb?

Here are some pictures of the carb in question.

 

[rigrunner]

not sure about a 273 but on my 318 the distributor only has one vacuume line going to it . it should be off the carb not the manifold. the manifold has constant pressure you want the distributor line on the passenger side of carb. the vacuum port on the back should be for a vacuum pull off for the original choke. would think you still need the fast idle cam for cold idle with choke on so it will run on it own without using your foot to keep it running. that port i would plug off and only run the one of the side to the distributor. hope this helps

 

[smlveightis]

x2 what rigrunner stated.

 

[tone]

Thanks for the advice. Makes sense. Rebuilding the carburetor also helped out a lot as well. I learned a lot more about how the carburetor works in the process.