Confused about vacuum advance

[lexicon]

Hi all - first post.

I'm running a Rover 3.5 with a Mallory DP dizzy and Holley 390 carb.
Currently fiddling with the ignition timing but I'm confused by what I've read about the vac advance. Some say it's connected to a ported vac line which has no effect at idle, others say when you re-connect the vac at idle you will see the timing advance, which is a direct contradiction.

What's the truth please - should the vauum advance be connected to ported or manifold vacuum?

Thanks in advance (no pun intended).

[GreenV8S]

As standard on the RV8 it is taken from a throttle edge tapping ('ported' as you put it). But it may still see some vacuum at idle, depending on the position of the port and how much throttle it takes at idle.

It seems tyo work fine (better in some ways) with the vac advance removed so I suspect it isn't that big a deal exactly how you plumb it up.

>> Edited by GreenV8S on Sunday 12th June 13:01

[lexicon]

OK, thanks.
I've been fiddling with it this afternoon and it's plumbed to the ported line - as you say it doesn't seem to make a lot of difference, connected or not.

[eliot]

I had mine plumbed into Manifold vacuum. Having vacuum advance at Idle is fine. Vac advance gives better mid/part throttle response (and apparentley fuel economy) - It makes no difference to wide open throttle. There was a very good and long explanation of how it should be plumbed. I think it was in the ultima forum, try searching or try Chris @ rpi.