Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

idles too high

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Cliff Ruggles:
Keep in mind that adding timing at idle is not needed for many applications.  In addition, a good ported source does EXACTLY the same thing as manifold vacuum right off idle, so fuel economy and engine efficieny are the same.

There are hundreds of pages of reading on this subject, some of it is very miss-leading as to how the vacuum advance works, and how it should be used.

My book describes it in detail.  There are "experts" out there that continue to advocate using MVA only, and that if you don't you are NOT doing it correctly.

The truth is that there are engine combinations out there that don't need that much timing at idle, and one quickly finds out that you can't get them to idle down and have control with the mixture screws running a lot of timing on them.  The educated tuner knows that they do NOT want that much timing.  Using a good ported source we can still give them the timing they need at light load (cruising) for best efficiency......Cliff

petro1143:
thanks cliff i have your book,,is the vacuum port on the base plate between mixture screws a ported vacuum?th only other vacuum port is up high and goes to transmission

Cliff Ruggles:
Test it with a vacuum gauge to make sure.  It should have no reading at idle, and FULL vacuum right off idle, or it isn't designed for distributor vacuum advance.....Cliff

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