performance curve distributor

The aftermarket distributors were made to be easy to modify the advance curves. Your factory ones weren't. With an aftermarket you could try different things easily and find what works best. A lot work with a factory distributor. If you knew what you needed, as far as how fast it comes in and how much mechanical advance is in the distributor, a couple of hours on a distributor machine would be all you need. Now as far as vacuum versus mechanical advance, if its a street car, use the vacuum advance. If you just use mechanical advance, you'll see your gas milage go down a lot (20%?).

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