loss of vacuum from carb to distributor

225 Buick V-6. I bead blasted and painted my distributor, installed pertronix 1165 ignition, and reinstalled it. Set idle and timing noting that my vacuum advance didn't change the timing when I plugged the vacuum line back on. Figured it was either stuck from paint or I got some media in the pot. Driving it indicated less power than before the changes were made. No biggie. I ordered a new vacuum advance and installed it tonight. When I plugged the vacuum line on to the pot, still no change in timing as indicated by my light. Turns out that the vacuum is weak from the port on the carb. I'm using the port at the lower front left of the carburetor, where it has always been hooked and previously worked fine. My vacuum gauge in the manifold port to the left and just rear of the carb shows 20". These descriptions are as I stand in front of the jeep. Why did I lose vacuum? Oh, yesterday I noticed the pcv valve was unplugged from the valve cover, so I plugged it back in.... probably unplugged it for room when I replaced the master cylinder this weekend....not sure that matters and I saw no change when I plugged and unplugged it tonight to see. Both vacuum advance units are good as they move fully with 15" according to my hand pump. Hmmm.
Your thoughts appreciated.

 

I don't think you should have any vacuum at the port for the distrbutor advance at idle.

 

Right.
That's ported vacuum, which increases as you open the throttle, as opposed to manifold vacuum, which drops off when you open the throttle.

 

OK, Im on board with that, but I always noted an increase in timing when I hooked that vacuum line back up. It doesn't move now at all...

 

Ported vacuum is just manifold vacuum that is physically blocked off by the throttle plate at idle.

The distributor advance could be connected to either ported or manifold vacuum, depending on the engine design and the mechanic. One or the other is correct from the factory, and both will work with proper tuning.

 

If it didn't change it some, why would we unplug it to set initial timing?

 

You want as smooth an idle possible so you won't get any timing chain slap which will cause your timing mark to jump around. That is just one reason.

 

You said timing was set. Is it set the same as before? The pertronix eliminated any point or lobe wear. This could explain the difference in the performance you noticed.

 

I reset the timing after the new ignition install and again after the new vacuum advance install as I pulled the distributor to make it easier.

Heres my thing. If you unplug the vacuum line on your 225 at idle, I bet the timing changes. Plug it back on and it will go back where it was. Mine isn't doing that anymore and that is all I'm pondering.

 

No timing chain slap in this one! Probably 15 hours on a complete rebuild.

 

You should not have any ported vacuum to the distributor at idle (idle 650-700 rpm). No the timing will not and should not change at idle when removing the ported vacuum line. If it does then you have a problem with the carb. Your idle adjust screws should be out about 2-1/2 to 2-3/4 turns or there abouts and idle smooth at 6-7 hundred rpm. Are you able to achieve this?