Ported vs full time vacum port

[greenpigs]

I set my timing to 15 adv like sugested. When I pluged my up to my full time port it didnt go up like before. It used to be 6 btdc and I use an eldebrock 750. So do I need to use the ported outlet? Is the motor "maxed" out making vacum so it didnt shoot up in idle. I could just switch using the ports but I would like to know why.

[elacruze]

What are you trying to do?

[Nacho-RT74]

distributor vacuum should use a ported vacuum source from carb. Hooks on to a non ported one, is the same that get it allways vacuum advanced, so the same than remove the vacuum and set it definitelly on that timming

[greenpigs]

I googled it and am preaty sure the ported port is what I should use also. All I want is the car to run as good as possible. MPG isn't important.

[TylerCharger69]

Set the timing with the distributor hose disconnected from the carb and the vacuum port plugged.....If that's what you are asking....

[greenpigs]

I was using full time or manifold  vacume. After timing change from 6 btdc to 15 advance manifold vacume doesn't seem to do much. So I use a ported source now and just wondered why I should.

[TylerCharger69]

but when you set the timing....that vacuum hose needs to be disconnected....

[maxwellwedge]

Here is a good little tuning tutorial for the "tinkerers".  http://www.sweptline.com/tech/engine2.html

[maxwellwedge]

Vacuum drawn from an opening ahead of the throttle is called ported vacuum. Throttle opening affects ported vacuum opposite to the way it affects manifold vacuum. For example, at closed throttle, manifold vacuum is at its peak. But there is no significant vacuum at a port ahead of the throttle plate when the throttle is closed. Vacuum appears at such a port only when the throttle opens.

It's important to remember that manifold vacuum is used to power vehicle systems that need a steady supply of low-pressure air under all engine operating conditions. These systems include power brake boosters, a/c vacuum motors and some emissions controls.
Ported vacuum is used to control vehicle systems in relation to engine load. These include distributor vacuum advance diaphragms and carburetor assist devices. They also include many emissions control devices and transmission shift points. Under some engine load conditions, ported vacuum may equal manifold vacuum, but it can never exceed it.

[greenpigs]

The vacum advance was disconected and the line pluged Tylar when I set timing.

[TylerCharger69]

okay....just checking....

[A383Wing]

Here's more: www.setyourtiming.com