Not a vette question but I have a car (a Ford, sorry : ) with a cam that only produces about 14" vacuum. No idea what the specs are but it drives poorly at lower RPM. I'm thinking the VAC is not correct. The stock cans are adjustable so I'd like to make a change. The 2" rule says (I think) that full vacuum should be in at 12" for my application. So here's the question. Is there an accurate procedure for adjusting the VAC using a vacuum pump? I checked directions for aftermarket VAC's and they want you to be a "human dyno" to figure out the correct setting. Any help?? Thanks!!
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Re: VAC question
Seems there's no experience with these things. Here's the plan of attack I came up with:
Apply vacuum at 8, 10, 14" of vacuum etc.. until the VAC pulls all of the throw and adjust as needed. Thoughts??
Is having the VAC pulled all the way in at 12" correct or have I misread the 2" rule?
Duke ?? -
Re: VAC question
I'm not familiar with Ford distributors, but you have interpreted the Two-Inch Rule correctly. If idle vacuum is 14" you need a VAC that is all in at no less than about 12", and, of course, it should be connected to a full time vacuum source.
I'm not sure what total vacuum advance should be, but since most vintage Ford engines have wedge combustion chambers, similar in design to vintage Chevrolet engines, I would expect the optimum to be in the range of 12- 16 degrees.
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