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Old 09-02-2012, 01:03 PM
1brewmaster1 1brewmaster1 is offline
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DoubleVision is right on target... There are MANY postings on the internet that argue the issue of ported vacuum (no vacuum at idle) and manifold vacuum (constant vacuum). The engine will run better, cooler, more effecient, faster and just about everything positive that is not mentioned when running off of manifold vacuum to the vacuum advance. Either take the vacuum off of the base of the carburetor or off of the intake manifold and your vacuum will do the rest. What ever your timing spec is, it will increase 12 - 14 degrees at idle when the manifold vacuum is applied. After modifying the vacuum source, readjust your idle and idle mixture screws and reset your idle again. Ported vacuum was introduced prior to the cat when polution control started controlling emissions. Instead of BTC (before top dead center), we went to ATC (after top dead center) and ported vacuum was required. Without all of the emissions on street built engines, ported vacuum is no longer needed.
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