82'ish Nikki 2bbl vacuum ports?

[pishta]

Forgive me in advance, I own a Mazda B2000! Anyway, I believe we share this same Nikki 2bbl carb and my question is: Are all 3 vacuum ports off the mixture screw side (3) the same ported vacuum level? My diagram shows the highest port is the Vacuum amplifier 'sense' line. Goes to that strange round thing on the package tray next to the wiper motor and then down to the EGR valve. The mid level port has a 90 bend on it and Its supposed to go to my purge control valve (via a thermo valve that opens when warm so it only pulls charcoal canister fumes when warm and off idle) and the lowest port goes to the vacuum advance. Does this sound about right? My concern is if the 2 lower ones are the same ported vacuum timing? the only thing manifold vaccum is the vacuum amp source, charcoal canister via purge control valve, anti backfire (gulp) valve and air cleaner shutter. I need all this shit to work in Cali for stupid smog inspections and I cant go easily to a Weber. Thanks in advance! 

[datzenmike]

Most all Datsuns are Hitachi carburetors. Nikki were on some '60s vehicles.

 

Hitachi's have a single ported vacuum till EGR was introduced around '73-ish. Later a TVV thermal vacuum valve was added to only allow EGR when warmed up. Usually the charcoal canister was run off the vacuum advance. Later, 720s had three ports, vacuum advance, canister purge and EGR.

 

Front one was canister purge, middle was vacuum advance and the rear one was EGR  (Last two were run through separate TVV) Later EGRs had an additional transducer valve that more closely varied the EGR in relation to exhaust back pressure. More throttle = more EGR.

 

All three were not directly connected to intake vacuum but to a port just above the throttle plate on the carburetor, so at idle it had no vacuum signal only ambient air pressure. As the throttle  plate rose up off of the idle position slowly the ports are exposed to intake vacuum. At WOT wide open throttle the vacuum signal was basically non existent so no vacuum advance or EGR.

 

If the signals were all the same and at the same throttle position only one port would be needed.