Advancing Timing

[bushbean]

What is the purpose for advancing the timing when the engine is cold?

I unplugged vacuum line #25 from the distributor, and didn't notice any difference when the engine is cold. The line had to be unplugged because there is vaccuum in line #25 even after the engine is fully warmed. I think the thermovalve is not opening properly.

[2oodoor]

Is there something wrong with the way you car is running?
there is supposed to be vacuum when warm. There are two vacuum connections at the dist. on is a little more advance than the other. the one with less advance is for cold , the other one with more advance is for warm running.

[cygnus x-1]

Right, the second port is for extra advance when cold. It's only like 4 degrees advance though so you likely won't even notice if it's not connected. The extra advance (supposedly) helps it run better when cold.

C|

[bushbean]

The car felt like it had a few less ponies, so I checked the timing. The timing is at the proper "24" mark when I disconnect line #25. The timing is not right when I reconnect line #25. All timing checks were done with engine fully warm.

I notice line #25 has vacuum all the time (even when warm). My understanding is that #25 should have no vaccuum after the cooland temperature gets warm.

[A20A1]

yes that is so, #25 should stop getting vacuum after the thermovalve is closed.
So either the valve is faulty or your coolant is low or is obstructed from getting to the valve, air bubbles can get in the way of the sensor as well.

When you set your timing you disconnect both #2 and #25 and set the distributor to TDC markings on the flywheel. Turn the distributor to adjsust if needed.

Then connect the vacuum lines and see if the other timing marks line up.
.

[2oodoor]

it is a good thing to make sure your centrifigal advance is working properley too.

once you have the timing set how you want it, remove the vacuum lines off the distributor again and hold the timing light on the mark, then very carefully throttle the engine up and see if the mark moves up when the engine is at higher rpm than idle.

[Versanick]

What if I lost track of what numbers are coming from where in the vacuum box?

Should both the vacuum ports coming from the distributor be attached to my intake manifold? Or before the throttle body on my cold air intake?

I'm confused at where these should be plugged in. I can't exactly figure it out.