Quote:
Originally Posted by Randy Rosenberg
I'm no expert here, but there seems to be a lot of discussion on the internet (google: ported vacuum advance) about whether to use "ported" or "manifold" vacuum for ignition timing advance.
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Ported spark was a failed attempt by auto makers to reduce hydrocarbons and oxides of nitrogen in the exhaust. As a result, the engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.
DO NOT, I repeat, DO NOT run ported spark. Connect your advance to a manifold (constant) vacuum source.