Hello all,

I want to make sure I hook up my 4100 vacuum correctly to my vac advance distributor. It was mentioned to me that I need ported vacuum to run my distributor correctly but some other people have said that manifold vacuum will work.

Upon further investigation on the WWW I seem to find that ported vacuum is actually what I need and manifold vacuum is a whole different animal in terms of how it works.

If indeed I do need to use ported vacuum to correctly operate my vac distributor, is there a designated connection on my 1965 C6ZF_B 4100 that is meant to be used in this way? I have been led to believe that the carb has such a ported vacuum connection on it but I sure as heck fire do not know exactly which one it is.

I am sincerely thankful for any reply which may help me see the light.

You are correct in what you are saying, you do need a ported vacuum port to run your distributor, and on the 4100 you have such a port.

It is located on the passengers side, at the base just forward of the choke assembly. Probably is a fitting already there with a metal tube.

Bill White
White Automotive

The wonders of the internet and similarly those here never cease to amaze me. I do have the connection where you have mentioned and it does have the metal tube. Thank-you for your most helpful reply.

Out of sheer curiosity, on a vehicle which is destined to be on the road with performance in mind, is this ported connection meant solely as means of emissions control or does it serve to act as something which allows the engine to perform better on the whole? I ask this because I am in a area which borders upon counties which if I need to, I may title a vehicle in a non-emissions area or one that requires emissions. I was hoping for, if possible, that I may take advantage of this and connect my vacuum connection appropriately for performance. Sorry if this sounds silly and thank-you again for any help.

The ported vacuum is based on carburetor vacuum which would be based on RPM of the engine which is what you want to run your distributor vacuum advance on, as compared to manifold constant vacuum which would have your distributor running at full advance all of the time, which is a nice way to limit the life of your engine......

Bill White
White Automotive