General Category > Quadrajet Carb Talk and Tips

which ported source to use.

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Cliff Ruggles:
Not sure what you are asking?

Ported vacuum to correctly operate the vacuum advance MUST supply FULL MANIFOLD VACUUM right off idle, or it will not work well.  This can be verified by using a vacuum gauge (two of them work best), on one MVA, the other on the ported source to the advance.  Off idle they should show approximately the same reading.....Cliff

68 Firebird:
Update

First off let me say, Cliff you we right.  I took your advice and tested the both vacuum ports
against a FMV source using two vacuum gauges.

 The lower left EGR port although it showed strong on takeoff it did bleed down some while cruising and never quite reached FMV.

The ported  port you added always had a strong signal off idle and remained steady at cruise.

Was interesting to watch how both gauges responded while driving.

Thanks

Gerry

Cliff Ruggles:
Cool.  Engine vacuum is based on engine load, so it always helps to do some active testing to see which port is really doing what?.....Cliff

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