Quote:
Originally Posted by flatjack9
If you are talking about an 8BA carb, it not ported vacuum, it is a combination of venturi and manifold vacuum and is less than manifold vacuum. On a modern engine, ported vacuum means it is closed off at idle, other than that it's the same as manifold vacuum.
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Jack, isn't it true that venturi vacuum increases when throttles open, while mainfold vacuum drops?
Isn't that why the load-a-matic distributor will retard timing instead of advance it when connected to manifold vacuum?