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low vacum

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dang:
working on  a 68 coup with a 289 2 barrel,what would cause low vacum getting only 10-12  on vacum?

Jeff73Mach1:
Vacuum is generated by the cyliders pulling air through the restriction of the carburetor.  Anything that affexts the amount of air drawn in will affect vacuum.

1st thing to look for are leaks, like a PCV port that is unplugged, then I would look at is timing,  With timing too far off the engine will not draw air through as quickly.  Idle speed can be the culprit, and then there are the mechanical issues such as worn rings not providing a good seal and even blown head gaskets.  Valves not seating can also cause problems.  here is a nifty gauge reading tool for the vacuum gauge 

http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm

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