I've noticed in photos of '66 Tri-Carb setups that they have ported vacuum for distributor advance taken off the center carb passenger's side. The center carbs on '66 Pontiacs were the same as the Olds, but I've never seen a Pontiac one with the ported vacuum provision. Pontiac used a hollow carb hold-down stud for manifold vacuum to the distributor advance.

There is a non-ported vacuum connection on the rear of the rear carb for vacuum to the heater controls.

I need this info for a setup I'm building for a '66 Olds. Anyone familiar with this?

 

Here's the setup I built. Ignore the Pontiac manifold. I used it since it has the same carb heights and distances as the Olds manifold. Should run great on the guy's '66 442! The linkage and lines fit very well. I added ported vacuum for the distributor advance from the center carb. Power brake vacuum comes off the front carb base same as Pontiac.

 

Good work. It looks nice.

 

A 90 deg. 1/8 NPT to 3/8" hose connection was at the rear of the center carb for PCV on the passenger side valve cover. The same sort of elbow on the back of the front carb fed the power brake booster. The distributor got vacuum from the ported 1/8 NPT source you mentioned on the center carb's fuel bowl.