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911pcars 911pcars is offline
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Join Date: Jul 2000
Location: So. Calif.
Posts: 19,910
Vacuum advance takes advantage of lean mixtures at part throttle (burn is slower), thus more ignition advance to take advantage; also increases fuel mileage.
At WOT = lower vacuum retards timing (thus no advance) from the vacuum mechanism.

If working properly, does not affect total mechanical (centrifugal) ignition advance.

Sherwood
Old 01-06-2018, 03:10 PM
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