FredMcJoe
Well-Known Member
I don't know where your vac is coming from.
Manifold vacuum at just below the throttle plates is the way cars were until the emission-minded 70s. The Carter on my 1977 Super Six slant 6 was ported to above the plates from a pipe on the upper right side of the carb. The benefit to having it at manifold vacuum is at idle, its at max vacuum advance. You want lots of advance to elongate the burn time of the relatively lean fuel mix (idle, closed throttle plates, lean mix of fuel being burned) which keeps the engine cooler.
This tended to increase emissions. The idea developed that using throttle vacuum, vacuum derived once the throttle plates opened, would reduce one of the emission particulates.. noxides comes to mind. Thus, the pipe out the right side of a Carter became the norm.
Manifold vacuum at just below the throttle plates is the way cars were until the emission-minded 70s. The Carter on my 1977 Super Six slant 6 was ported to above the plates from a pipe on the upper right side of the carb. The benefit to having it at manifold vacuum is at idle, its at max vacuum advance. You want lots of advance to elongate the burn time of the relatively lean fuel mix (idle, closed throttle plates, lean mix of fuel being burned) which keeps the engine cooler.
This tended to increase emissions. The idea developed that using throttle vacuum, vacuum derived once the throttle plates opened, would reduce one of the emission particulates.. noxides comes to mind. Thus, the pipe out the right side of a Carter became the norm.
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