Most experts suggest a stock engine run a ported connection. A hotter street driven engine should try a manifold connection. In all cases experts agree that a street driven engine should run vacuum advance.

Is vacuum advance ported or manifold?

The only difference between the two, is that manifold source would give you vacuum advance at idle, ported source gives you the same manifold vacuum, but only once the throttle is cracked open.

Does vacuum advance go ported vacuum?

Using a ported spark advance will still allow the vacuum advance to do its job at steady cruising, but all of the benefits of idle cooling will be lost. Heres a quick experiment you can try on your car. Plug the vacuum advance into a ported vacuum source and check the idle rpm.

What is ported manifold vacuum?

Ported vacuum is vacuum that is low at idle and increases as you give it gas. Attached to your distributor it will cause the vacuum advance to move quickly to increase performance and drop off when you let off on the gas for a smoother idle.

Where should the vacuum advance?

This can be checked with the engine running at idle with a timing light. Make sure the vacuum advance connection is removed, and now rev the engine up to around 2,500 to 2,800 rpm. Ideally, the timing now should be somewhere around 34 to 36 degrees to total advance.

What happens when vacuum advance fails?

Eventually the deterioration will reach the point that the vacuum advance no longer adjusts the timing, causing the vehicle to hesitate when the engine attempts to move the vehicles weight. In addition to this lack of power, a vacuum leak can also cause the engine to idle roughly or even stall.

Is vacuum advance necessary?

The vacuum advance provides this benefit BEFORE the Mechanical Advance provides Total Timing. Vacuum advance distributors are best for street vehicles. The vacuum advance feature has NO EFFECT on full-throttle power. They provide no benefit for engines that spend most of their life at high rpm (race engines).

When should vacuum advance start?

If your engine idles at 10 inches Hg or less, you can start the tuning process by setting the initial timing to at least 15 degrees BTDC. If your car is equipped with an automatic transmission, placing it in gear may pull the manifold vacuum down even further.

How do I know if my vacuum advance is working?

0:040:47Vacuum Advance - How to Test - YouTubeYouTube