Thread: Kind of a Drag

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Vacuum advance works great on a street motor, I use it on all of mine. It helps the gas millage at cruise speeds and helps motor to run cooler. Some motors like the ported advance (above throttle blades), some like it on manifold. Manifold will usually increase idle speed and is useful when trying to get idle speeds up without adding too much throttle blade.

Be careful using manifold vacuum as a crutch with a big cam to get it to idle, when you brake hard quickly after accelerating the motor will usually die because the vacuum can't recover fast enough to pull idle speed back up.