What is the difference between mechanical advance and vacuum advance ? :confused:

 

Mechanical advance - this is a form of timing adjustment that advances the timing by using the centrifigal force that is exerted to the two weights on the distributor which propels them to pivot outward. The movement of the weights moves a pivot arm under the weights which moves and advances the timing of the engine. Mechanical advance can be adjusted by using larger/heavier weights or smaller/lighter weights, but is more commonly adjusted through the changing of the two small springs that pull the wieghts back to their "home" position when the distributor is not spinning or is not spinning with enough inertia to move them. Lighter spring allows the enigne RPM's to spin the weights out faster in the RPM band and advance timing sooner.

Vacuum Advance - this is a form of engine timing adjustment that uses the vacuum which is generated by the pistions going up and down, to be tapped into and directed to a vacuum canister on the side of the distributor on the outside of the housing. Though part of the vac canister is extended into the distributor. As the engine picks up speed and creates more vacuum, since the pistons are going up and down quickly the vacuum pulls on the diaphram inside the vac canister and this in turn pulls on a rod that is connected to a plate inside the distibutr which advaces the timing.

Put your vocabulary sheets away students. Autoshop class.....dismissed!
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"TEACH"