I'm trying to sort out some idle/vac issues with my project and have some basic carb questions. At the dist adv port on the rear carb, what vac reading should I be getting at sub 900 RPM? Shouldn't it be much lower than manifold vac... and come in as RPMs go up? I'm getting 12in of manifold vac @ 900RPM but also am getting the exact same reading at the dist advance port. That surely can't be right. Any insight out there?

I'm ing myself

Sandy,
I have Monday off from work so it will be a day in the garage. I can take some vacuum measurements for you. I know your cam is bigger than stock so you will need to adjust for it. The ported vacuum off the carb should be almost nothing until you crack open the thottle blades. If your rear carb has the idle screws in a bit and the speed screw adjusted more in for a faster speed or to compensate for less initial distributor advance you could be seeing the higher vacuum. I don't think that you would see the same as manifold vacuum. I know on my dual point that around 8-9 inches will start to move the advance plate and I think by 15 inches I have full advance. I can call your cell mid morning to talk.

Jim