Thread: mechanical vs. vacuum advance

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A vacuum advance dist . will get better mileage and will run better in stop and go driving . the mechanical will get better times on the drag strip . i have tried using the vacuum then unplugging it and making a pass with the vacuum locked out the car is a .05 quicker with out vac -ad .

Would this also hold true for a blown motor?

Distributors with vacuum advance in modern engines commonly used in hot rods always have mechanical advance.


If you have the same mechanical advance curve in a distributor that also has vacuum advance then how does a racing oriented strictly mechanical advance distributor turn better times?


Mechanical advance responds to rpm and vacuum advance responds to load.

Since an engine under full power has a vacuum level very close to zero, the vacum advance is backed all the way off and all the engine gets as far as spark advance goes is what's allowed by the mechanical advance system.