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racing has one need, WOT. a mechanical advance with no vac can will provide this. set it and forget it. Off you go.

If you cruise around an drive it distance and varied, the vacuum is almost esential for a smmoth nice ride. with no load a performance engine may love 30-50total timming cruising part throttle. As load inscreases hills/weight/restisitance/foot the advance goes away, and the flame front hits the piston harder, with the reduced timming.

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racing has one need, WOT. a mechanical advance with no vac can will provide this. set it and forget it. Off you go.

If you cruise around an drive it distance and varied, the vacuum is almost esential for a smmoth nice ride. with no load a performance engine may love 30-50total timming cruising part throttle. As load inscreases hills/weight/restisitance/foot the advance goes away, and the flame front hits the piston harder, with the reduced timming.

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Hence the reason production vehicles have a vaccum advance. But would a MSD Pro-billet distributer,with its spring style set-up, not work the same as a vaccum advance?

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Could someone explain the differences (pros and cons) of a distributer with vaccum advance and one that is mechanical. Or when you would chose one over the other.

Thanks

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Stock has both

mechanical timing's main purpose is to compensate for timing needs, at different engine speeds. The amount you have , and when you need it will vary with application.

Vacuum advance is for improved economy at cruise.

Properly set up, a vehicle should not run or perform any different without vacuum advance. It's main purpose is economy.

As for not running vacuum....
Wilder combo's see virtually no improvement in economy with Vacuum advance(hard to imporve on 5mpg in cammed up car), and the vacuum advance can be a bit of a hinderent on wilder 4 gear cars, as it will try to ad some timing between shifts. Can cause the plate to get hung up etc...

I delete vacuum advance when curving more radical builds, but leave it on for most street cars.

FWIW, I do street drive my own, and have no vacuum advance. It has never had a drivability problem, or overheat etc..

The vacuum advance debate can get ugly. Reality is, having a good initial timing value, and a curve to match your combo is what's most important

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The weights and springs alone are the mechanical advance curve. No correspondance to load at variable throttle. Not anything like the benefit of a vacuum can.

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