WebApr 12, 2012 · When emissions became mandated, vacuum systems went to ported. This reduced emissions (NOx I think), but if you run this way, you have to adjust your settings to prevent too much advance under load, because the ported vacuum provides advance with venturi velocity. WebAug 21, 2024 · 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. Ported …
ported vacuum on quadrajet question Team Chevelle
WebFeb 11, 2012 · Premium Member. 1970 SS454 LS6 11 second street car. Joined May 8, 1999. 19,825 Posts. #5 · Feb 9, 2012. once the throttle plates open,it doesnt matter if its ported or vacuum at that point. Manifold vacuum does help at idle if you have a large cam. My 1970 SS454 LS6 SuperCar certified stock appearing 11.90@113 MPH. WebNov 24, 2004 · Full vacuum gives you all the vacuum advance at idle, and the engine gets only the mechanical advance increase as RPMs go up. Ported vacuum allows both … crystal for positivity
ported or manifold vacuum for advance? - Ford Muscle …
WebDec 22, 2024 · the mechanical advance takes over from the vacuum as rpm goes up and vacuum decreases. There is a lot of debate on weather to use ported or full manifold vacuum and best to see which works best for each individual application. I think most around here tend to go with full manifold vacuum. WebJan 30, 2004 · The advent of smog rules in the late '60's & early '70's brought the use of ported vacuum. Vacuum advance at idle makes a car idle smoother & with less throttle opening, but it also increases emissions. Later cars with distributors designed for ported vacuum should probably use it. WebJul 9, 2007 · Discussion Starter · #1 · Jul 9, 2007. I have a 70 SS 402/350, th400, and a quadrajet carb and I cannot locate ported vacuum on the carb. I recently installed a new distributor and currently have my initial timing at 16 degrees with a total of 36 degrees with the vacuum advance unhooked from the distributor and plugged. d-way services limited