do you have to have the dstributor vaccum line hooked up to make it run

[pete29]

wondering if you have to have the distributor vaccum line hooked up that connects the carb to distributor to make the engine run, what does it do.

[Critter]

You don't have to have it hooked up to start the engine, but it won't run right with out it. It is called "vacuum advance". Basically when the motor increases in RPM, that vacuum line activates a lever inside your distributor and adjusts the timing to match your engine speed. You would not be able to properly tune an engine if it wasn't connected. There is A LOT more to it than what I just said, but that is the basic idea. Just do a search on vacuum advance and you will find more info than you can handle.

plus look at these sites...

http://www.stoveboltengineco.com/howto/vac.htm

http://www.2quicknovas.com/happytiming.html

[Burt4x4]

Yup, first is your mechanical advance, and the RPM increases the weights inside the dist. spin faster and open up or advance the timing, the vacum advance finnishes up the final timing setting. I had an MSD dist on my 350 that you could swap the springs to adjust the mechn. timing with vac line pluged. then set final timing with vac hooked up...
somethign like that anyway...
good luck
Burt

[pumpkin]

Vacuum advance is used for fuel economy. For the most part, when I am setting up an engine to make power I don't use it. It can become a bit unpredictable and require adjustable vacuum dash pot. The best way to set your timing is to set the full advance to 38-42 degrees. The problem with this, is depending on the advance curve in the dist. you may have to rev the engine too high. One I just set up for a guy, almost doubled his power, and got rid of the pinging. one problem that can come up with a stock dist, is that the base timing can end up too much and make the engine hard to start when hot.