Quote Originally Posted by 53 Chevy5 View Post
If I use ported vacuum, wouldn't that completely make the mechanical weights obsolete because the vacuum increases as you rev the engine up therefore advancing the timing?
No, vacuum advance wether manifold or ported sourced will not effect your mechanical, they are two separate things.

And, the only difference between manifold and ported is when the vacuum advance starts. Manifold is at idle through cruise rpm, ported is off at idle and comes on at cruise rpm. Ported is also known as TIMED because it comes on later.

Simply put, vacuum advance is an economizer, it has nothing to do with performance. In theory, at idle and cruise speeds the motor can use more advance to burn leaner mixtures. However, I'm a big believer in giving the motor what the motor wants.

If the advance at idle brings the idle speed up too high, plug it into ported, you'll still have it at cruise for economy. If it idles good on manifold great, leave it there.