What is the purpose of a timed carb vacuum port? My Carter 9637 SA AFB has three vacuum ports in front at base of carb. The middle one goes to the PCV valve, the right one (from front of engine) is at full vacuum and is plugged. The left one is connected to a TVS that has control over vacuum advance. At engine idle there is no vacuum at the timed port.
mike
"goodnigh" wrote in news:BvQ0h.1120$zf.58 @newsread3.news.pas.earthlink.net:
Because you don't want distributor advance at idle. You want it under acceleration and at speed.
On most carburettors, we are given acces to both manifold vacuum and "ported" vacuum... Ported vacuum is derived from above the throttle plate but below the venturi.... Some carbs also have provisions for venturi vacuum... but this is a very weak signal at the best of times.
Ford has used ported vacuum extensively for vacuum advance application. During the late 70s/early80s, they also used both ported and manifold vacuum for the distributor through a temperature sensitive vacuum valve (manifold vacuum when cold - ported vacuum after warm-up). Ported vacuum has also been used for EGR operation. Venturi vacuum was used in some years to control a vacuum amplifier which, in turn, controlled the EGR....
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