Quote:
Originally Posted by DanEC
Patrick - I'm not sure I understand how that would work? If the idle is jumping up because of additional air pulled in through the vacuum circuit below the butterflies when uncapped - how would it ever be able to be equalized? What did you do other than just back your mixture screws out equally by 1-1/2 turns, or 2 turns, etc?
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My traditional vacuum gauge method was to adjust the mixture screws to achieve the highest vacuum at idle. That worked reasonably well. But, with a large overlap cam, vacuum is low and the response of the gauge needle is not instantaneous.
The old Ford service tech's method is, at least on the internet, almost totally undocumented. The only doc I could find that said the same thing was Tip #3 here:
12 Carb and Fuel System Tech Tips - Muscle Car Review Magazine
Now, I will say the "pull the vacuum plug" method gives you instant feedback. It was exceptionally easy, it resulted in different idle mixture settings from what I had with the vacuum gauge, and my car runs astoundingly well adjusting it his way. For me, and my setup, that is the way I will always do it from now on. It may not work for others. The only reason he mentioned it to me was that, after we chatted for a while, he remembered the specs of my original Ford "K" cam, along with a single four barrel, and how they dealt with getting the carb set just right when the cam was causing a lumpy, low vacuum idle.
I must admit that, at the time, I did not think his technique had any merit. But testing it out was as easy as pie....