Vacuum Advance or Retard?

[Paulporsche]

My engine is a mongrel, including using an S dizzy. There is only 1 port off the vacuum unit and it is located on the top. Is this an advance or retard?

In either case, is it necessary? I do not have to worry about emissions testing, I would just like to get the best running condition.

[Bill Verburg]

Put vacuum on it and see.

[Paulporsche]

Bill,

I don't have a vacuum pump. Will ordinary lung power be sufficient? If it is a retard, will I hear the revs decrease, or if advance, increase? Or do I need to hook up a timing light?

I read an old post by (I think) Early S Man, who said these were retard units. If so, apparently I can disconnect it for a better idle. Can it remain open or should the port be plugged?

[Bill Verburg]

Lung power will do it.

At idle, retard will generally slow the engine, advance will speed it up.