Do the 12a's have secondary intake ports? If so how are they opened? I was reading about how the 13b 6 ports were back pressure actuated and was wondering if the 12a was the same if it indeed does have secondary ports.

most 12A's are 4 port like the later turbo engines, they do run a 4 barrel carburetor though, so it runs from the primary 2 barrels/ports until load gets high enough and then the secondaries can open.



in japan, they DID have a 6 port 12A, its actually the precursor to the 13B EFI versions. it keeps the 4 barrel carb, but adds the 5th and 6th ports like the later engines. i believe that these did use exhaust backpressure to open the ports.

I learn something new everyday! Lol were the nikkis running large jets to go with the higher flow or any other mods of that sort?

I thought the 6 Port 12A was the the Turbo EFI one? I dont remember reading anything about a 6 port Carb version. Though i could be wrong. But I do know that The Savannah was Trubo EFI and thats why the Turbo II was dubed Turbo II. Ill have to look around to be sure. But j9fd3s is right about the 4 port carbed

Oh ok thanks man, I was just tryin to make sure I didn't completely disable anything by adding a better flowing exhaust.

6 port 12a was produced for the European market