Which Is Better Ported or Manifold Vacuum?

If you can run manifold vacuum it's certainly worth a try. It is also true that manufacturers increasingly used retarded timing strategies at idle to keep NOX emissions down. Most experts suggest a stock engine run a ported connection. A hotter street driven engine should try a manifold connection.

Does vacuum advance go to ported or manifold vacuum?

The only difference between the two, is that manifold source would give you vacuum advance at idle, ported source gives you the same manifold vacuum, but only once the throttle is cracked open.

Does ported vacuum increase with RPM?

Plug the vacuum advance into a ported vacuum source and check the idle rpm. ... Because the additional ignition timing provided by the vacuum canister and full manifold vacuum source allowed the engine to more effectively burn the air/fuel mixture. It therefore produces more power (even at idle) and rpm rises as a result.