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Discussion Starter #1
I have an edelbrock carb and intake manifold as well as a Pertronix Ignitor II replacing the points in my distributor. Do I need to have all the vacuum hoses attached to this port:

P1030203.jpg
P1030200.jpg

As you can tell from the pics, I currently don't have any of them attached, but was wondering if I should reconnect them. Is this necessary given my current application?

I'm also looking at replacing the distributor and getting an MSD distributor that doesn't require the ignition box. Would I need this port/vacuum lines if I switch out distributors? Thoughts/recommendations?
 

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Those vacuum ports appear to be off the intake. Those ports could be used to hook up the vacuum advance if your new distributor had that or also if you use a high end fuel regulator that takes the amount of vacuum from the motor as reference in how much fuel to feed the carb. I'd suggest finding the MSD you want and researching if it takes a mechanical advance or vacuum advance, then you will know if the ports are to be used or not. Good luck :)
 

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The answer is NO, if you need vacuum for the dist. take it from the timed port of the carb..
 

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That three-port thing is what is known as a thermal vacuum switch. It screws into a coolant passage. The premise is that there is one vacuum supply line and two other vacuum ports. Below a certain temp, the vacuum goes to one, and above that temp it is switched to the other.
 

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Actually there are two vacuum sources, one from the timed port on the carb, and the other from the manifold. In most cases, when the engine starts to run hot, the vacuum source is switched to from the timed port to manifold vacuum to increase the engine idle speed. THis speeds up the water pump and also the cooling fan. In a few rare cases, it is set up exactly backwards so it slows down the engine when it starts to run hot (CJ 351C in '71 Pantera, uses electric fans for cooling)
 

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Discussion Starter #6
Thanks! This does help! Now I actually know why this thing was there. I just have to figure out which vacuum lines are needed and where they go. Thank God for Chilton's vacuum diagrams!
 
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