General Category > Quadrajet Carb Talk and Tips

7040202 APT

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mcx:
Cliff..I found my answer here..https://cliffshighperformance.com/simplemachinesforum/index.php?topic=1066.0

Cliff Ruggles:
Yes, 1970 was a goofy year for carburetors as the factory used TCS to the vacuum advance instead of directly from the carburetor via ported vacuum.

When a Q-jet is set-up to apply the vacuum advance via ported vacuum it is "all in" right off idle as they used a very precisely located hole in the baseplate that is completely uncovered with very little throttle movement.

Even so you'll read all over the NET that your an idiot if you don't use MVA to the distributor with rumors of extra cooling to improved fuel economy to not pinging at heavy and WOT. 

ALL of that for the most part is just regurgitated and outdate information on the subject.  The real truth is that the ONLY difference between using MVA and ported (with a correctly located source) is that you have no vacuum advance idle and coasting, it is exactly the same in all other scenarios.......Cliff

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