Thread: 30 degrees of advance at idle?

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I can't see hooking my vacuum advance to manifold vacuum instead of ported vacuum,you'd lose all vacuum advance when you open the throttle,and still waiting for the mechanical to come in. Hank

If you read the above linked article, I think it explains this better than I could defend.

I understand your point of view, I used to be there. But now I am (so far) convinced that Manifold vacuum is the right way to go when set up properly in combination with the other factors.

I conclude this from reading many articles here (mostly from C9x), and the linked article. Read these:

http://www.clubhotrod.com/forums/sho...vance+canister

http://www.clubhotrod.com/forums/sho...vance+canister

http://www.clubhotrod.com/forums/sho...=ported+vacuum

Originally Posted by DennyW

.....Besides, the vacuum wouldn't start coming in until you reached the mid-upper rpm's anyway. Same as the ported vacuum does. ...

Denny, I am very confused by this comment, do you mean the vacuum would not start coming in until mid to upper rpms with manifold vacuum? When my engine is at idle, it pulls vacuum of 20. That is the max vacuum ever from the manifold, and therefore maximum vacuum advance.

Also, the one part about this I still don't get (about the overheating issue) is that I was taught that the more advanced the timing is, the hotter the engine will run. Using manifold vacuum will have the most timing at idle when you are sitting in traffic. I'm sure there is something I'm missing if you can help clear it up for me.

So as to not throw this discussion off track, I'll post a manifold vacuum vs ported vacuum article I did a while back and - far as I know - never posted here.

Titled: More about vacuum sources and timing.